Rushing to Judgment (Global Warming Questioned

Is Earth warming? The planet has warmed since the mid-1800s, but before that it cooled for more than five centuries. Cycles of warming and cooling have been part of Earth’s natural climate history for millions of years. So what is the global warming debate about? It’s about the proposition that human use of fossil fuels has contributed significantly to the past century’s warming, and that expected future warming may have catastrophic global consequences. But hard evidence for this human contribution simply does not exist; the evidence we have is suggestive at best. Does that mean the human effects are not occurring? Not necessarily. But media coverage of global warming has been so alarmist that it fails to convey how flimsy the evidence really is. Most people don’t realize that many strong statements about a human contribution to global warming are based more on politics than on science. Indeed, the climate change issue has become so highly politicized that its scientific and political aspects are now almost indistinguishable. The United Nations Intergovernmental Panel on Climate Change (IPCC), upon which governments everywhere have depended for the best scientific information, has been transformed from a bona fide effort in international scientific cooperation into what one of its leading participants terms “a hybrid scientific/political organization.”

Yet apart from the overheated politics, climate change remains a fascinating and important scientific subject. Climate dynamics and climate history are extraordinarily complex, and despite intensive study for decades, scientists are not yet able to explain satisfactorily such basic phenomena as extreme weather events (hurricanes, tornadoes, droughts), El Niño variations, historical climate cycles, and trends of atmospheric temperatures. The scientific uncertainties about all these matters are great, and not surprisingly, competent scientists disagree in their interpretations of what is and is not known. In the current politicized atmosphere, however, legitimate scientific differences about climate change have been lost in the noise of politics.

For some, global warming has become the ultimate symbol of pessimism about the environmental future. Writer Bill McKibben, for example, says, “If we had to pick one problem to obsess about over the next 50 years, we’d do well to make it carbon dioxide.” I believe that we’d be far wiser to obsess about poverty than about carbon dioxide.

Fossil fuels (coal, oil, and natural gas) are the major culprits of the global warming controversy and happen also to be the principal energy sources for both rich and poor countries. Governments of the industrial countries have generally accepted the position, promoted by the IPCC, that humankind’s use of fossil fuels is a major contributor to global warming, and in 1997 they forged an international agreement (the Kyoto Climate Change Protocol) mandating that worldwide fossil fuel use be drastically reduced as a precaution against future warming. In contrast, the developing nations for the most part do not accept global warming as a high-priority issue and, as yet, are not subject to the Kyoto agreement. Thus, the affluent nations and the developing nations have set themselves on a collision course over environmental policy relating to fossil fuel use.

The debate about global warming focuses on carbon dioxide, a gas emitted into the atmosphere when fossil fuels are burned. Environmentalists generally label carbon dioxide as a pollutant; the Sierra Club, for example, in referring to carbon dioxide, states that “we are choking our planet in a cloud of this pollution.” But to introduce the term pollution in this context is misleading because carbon dioxide is neither scientifically nor legally considered a pollutant. Though present in Earth’s atmosphere in small amounts, carbon dioxide plays an essential role in maintaining life and as part of Earth’s temperature control system.

Those who have had the pleasure of an elementary chemistry course will recall that carbon dioxide is one of the two main products of the combustion in air of any fossil fuel, the other being water. These products are generally emitted into the atmosphere, no matter whether the combustion takes place in power plants, household gas stoves and heaters, manufacturing facilities, automobiles, or other sources. The core scientific issue of the global warming debate is the extent to which atmospheric carbon dioxide from fossil fuel burning affects global climate.

When residing in the atmosphere, carbon dioxide and water vapor are called “greenhouse gases,” so named because they trap some of Earth’s heat in the same way that the glass canopy of a greenhouse prevents some of its internal heat from escaping, thereby warming the interior of the greenhouse. By this type of heating, greenhouse gases occurring naturally in the atmosphere perform a critical function. In fact, without greenhouse gases Earth would be too cold, all water on the planet would be frozen, and life as we know it would never have developed. In addition to its role in greenhouse warming, carbon dioxide is essential for plant physiology; without it, all plant life would die.

A number of greenhouse gases other than carbon dioxide and water vapor occur naturally in Earth’s atmosphere and have been there for millennia. What’s new is that during the industrial era, humankind’s burning of fossil fuels has been adding carbon dioxide to the atmospheric mix of greenhouse gases over and above the amounts naturally present. The preindustrial level of 287 parts per million (ppm) of carbon dioxide in the atmosphere has increased almost 30 percent, to 367 ppm (as of 1998).

Few, if any, scientists question the measurements showing that atmospheric carbon dioxide has increased by almost a third. Nor do most scientists question that humans are the cause of most or all of the carbon dioxide increase. Yet the media continually point to these two facts as the major evidence that humans are causing the global warming Earth has recently experienced. The weak link in this argument is that empirical science has not established an unambiguous connection between the carbon dioxide increase and the observed global warming. The real scientific controversy about global warming is not about the presence of additional carbon dioxide in the atmosphere from human activities, which is well established, but about the extent to which that additional carbon dioxide affects climate, now or in the future.

Earth’s climate is constantly changing from natural causes that, for the most part, are not understood. How are we to distinguish the human contribution, which may be very small, from the natural contribution, which may be small or large? Put another way, is the additional carbon dioxide humans are adding to the atmosphere likely to have a measurable effect on global temperature, which is in any case changing continually from natural causes? Or is the temperature effect from the additional carbon dioxide likely to be imperceptible, and therefore unimportant as a practical matter?

Global warming is not something that happened only recently. In Earth’s long history, climate change is the rule rather than the exception, and studies of Earth’s temperature record going back a million years clearly reveal a number of climate cycles—warming and cooling trends. Their causes are multiple—possibly including periodic changes in solar output and variations in Earth’s tilt and orbit—but poorly understood. In recent times, Earth entered a warming period. From thermometer records, we know that the air at Earth’s surface warmed about 0.6ºC over the period from the 1860s to the present. The observed warming, however, does not correlate well with the growth in fossil fuel use during that period. About half of the observed warming took place before 1940, though it was only after 1940 that the amounts of greenhouse gases produced by fossil fuel burning rose rapidly, as a result of the heavy industrial expansions of World War II and the postwar boom (80 percent of the carbon dioxide from human activities was added to the air after 1940).

Surprisingly, from about 1940 until about 1980, during a period of rapid increase in fossil fuel burning, global surface temperatures actually displayed a slight cooling trend rather than an acceleration of the warming trend that would have been expected from greenhouse gases. During the 1970s some scientists even became concerned about the possibility of a new ice age from an extended period of global cooling (a report of the U.S. National Academy of Sciences reflected that concern). Physicist Freeman Dyson notes that “the onset of the next ice age [would be] a far more severe catastrophe than anything associated with warming.”

Earth’s cooling trend did not continue beyond 1980, but neither has there been an unambiguous warming trend. Since 1980, precise temperature measurements have been made in Earth’s atmosphere and on its surface, but the results do not agree. The surface air measurements indicate significant warming (0.25 to 0.4ºC), but the atmospheric measurements show very little, if any, warming.

Briefly, then, the record is this: From 1860 to 1940, Earth’s surface warmed about 0.4ºC. Then Earth’s surface cooled about 0.1ºC in the first four decades after 1940 and warmed about 0.3ºC in the next two. For those two most recent decades, temperature measurements of the atmosphere have also been available, and, while these measurements are subject to significant uncertainty, they indicate that the atmosphere’s temperature has remained essentially unchanged. Thus, the actual temperature record does not support the claims widely found in environmental literature and the media that Earth has been steadily warming over the past century. (A new study that may shed more light on this question—one of a number sure to come—has been circulated but is being revised and has not yet been published.)

For the probable disparity between the surface and atmospheric temperature trends of the past 20 years, several explanations have been offered. The first is that large urban centers create artificial heating zones—“heat islands”—that can contribute to an increase of surface temperature (though one analysis concludes that the heat island effect is too small to explain the discrepancy fully). The second explanation is that soot and dust from volcanic eruptions may have contributed to cooling of the atmosphere by blocking the Sun’s heat (though this cooling should have affected both surface and atmospheric temperatures). In the United States, despite the presence of large urban areas, surface cooling after 1930 far exceeded that of Earth as a whole, and the surface temperature has subsequently warmed only to the level of the 1930s.

It’s frequently claimed that the recent increases in surface temperature are uniquely hazardous to Earth’s ecosystems because of the rapidity with which they are occurring—more than 0.1ºC in a decade. That may be true, but some past climate changes were rapid as well. For example, around 14,700 years ago, temperatures in Greenland apparently jumped 5ºC in less than 20 years—almost three times the warming from greenhouse gases predicted to occur in this entire century by the most pessimistic scientists.

Whatever the current rate of surface warming, there is little justification for the view that Earth’s climate should be unchanging, and that any climate change now occurring must have been caused by humans and should therefore be fixed by humans. In fact, as noted earlier, changing climate patterns and cycles have occurred throughout Earth’s history. For millions of years, ice sheets regularly waxed and waned as global heating and cooling processes took place. During the most recent ice age, some 50,000 years ago, ice sheets covered much of North America, northern Europe, and northern Asia. About 12,000 years ago a warming trend began, signaling the start of an interglacial period that continues to this day. This warm period may have peaked 5,000 to 6,000 years ago, when global ice melting accelerated and global temperatures became higher than today’s. Interglacial periods are thought to persist for about 10,000 years, so the next ice age may be coming soon—that is, in 500 to 1,000 years.

Within the current interglacial period, smaller cyclic patterns have emerged. In the most recent millennium, several cycles occurred during which Earth alternately warmed and cooled. There’s evidence for an unusually warm period over at least parts of the globe from the end of the first millennium to about 1300. A mild climate in the Northern Hemisphere during those centuries probably facilitated the migration of Scandinavian peoples to Greenland and Iceland, as well as their first landing on the North American continent, just after 1000. The settlements in Greenland and Iceland thrived for several hundred years but eventually were abandoned when the climate turned colder, after about 1450. The cold period, which lasted until the late 1800s, is often called the Little Ice Age. Agricultural productivity fell, and the mass exodus to North America of many Europeans is attributed at least in part to catastrophic crop failures such as the potato famine in Ireland.

A plausible interpretation of most or all of the observed surface warming over the past century is that Earth is in the process of coming out of the Little Ice Age cold cycle that began 600 years ago. The current warming trend could last for centuries, until the expected arrival of the next ice age, or it could be punctuated by transient warm and cold periods, as were experienced in the recent millennium.

A great deal of global warming rhetoric gives the impression that science has established beyond doubt that the recent warming is mostly due to human activities. But that has not been established. Though human use of fossil fuels might contribute to global warming in the future, there’s no hard scientific evidence that it is already doing so, and the difficulty of establishing a human contribution by empirical observation is formidable. One would need to detect a very small amount of warming caused by human activity in the presence of a much larger background of naturally occurring climate change—a search for the proverbial needle in a haystack.

Still, understanding climate change is by no means beyond science’s reach, and research is proceeding in several complementary ways. Paleoclimatologists have been probing Earth’s past climatic changes and are uncovering exciting new information about Earth’s climate history going back thousands, and even millions, of years. This paleohistory will help eventually to produce a definitive picture of Earth’s evolving climate, and help in turn to clarify the climate changes we’re experiencing in our own era. But we are far from knowing enough to be able to predict what the future may hold for Earth’s climate.

Mindful of the limited empirical knowledge about climate, some climate scientists have been attempting to understand possible future changes by using computer modeling techniques. By running several scenarios, the modelers obtain a set of theoretical projections of how global temperature might change in the future in response to assumed inputs, governed mainly by the levels of fossil fuel use. But like all computer modeling, even state-of-the-art climate modeling has significant limitations. For example, the current models cannot simulate the natural variability of climate over century-long time periods. A further major shortcoming is that they project only gradual climate change, whereas the most serious impacts of climate change could come about from abrupt changes. (A simple analogy is to the abrupt formation of frost, causing leaf damage and plant death, when the ambient air temperature gradually dips below the freezing point.) Given the shortcomings, policymakers should exercise considerable caution in using current climate models as quantitative indicators of future global warming.

Scientists have long been aware that physical factors other than greenhouse gases can influence atmospheric temperature. Among the most important are aerosols—tiny particles (sulfates, black carbon, organic compounds, and so forth) introduced into the atmosphere by a variety of pollution sources, including automobiles and coal-burning electricity generators, as well as by natural sources such as sea spray and desert dust. Some aerosols, such as black carbon, normally contribute to heating of the atmosphere because they absorb the Sun’s heat (though black carbon aerosols residing at high altitudes can actually cool Earth’s surface because they block the Sun’s rays from getting through to it). Other aerosols, composed of sulfates and organic compounds, cool the atmosphere because they reflect or scatter the Sun’s rays away from Earth. Current evidence indicates that aerosols may be responsible for cooling effects at Earth’s surface and warming effects in Earth’s atmosphere. But the impacts of pollution on Earth’s climate are very uncertain. The factors involved are difficult to simulate, but they must be included in computer models if the models are to be useful indicators of future climate. When climate models are finally able to incorporate the full complexity of pollution effects, especially from aerosols, the projected global temperature change could be either higher or lower than current projections, depending on the chemistry, altitude, and geographic region of the particular aerosols involved. Or, it could even be zero.

In addition to pollution, other physical factors that can influence surface and atmospheric temperature are methane (another greenhouse gas), dust from volcanic activity, and changes in cloud cover, ocean circulation patterns, air-sea interactions, and the Sun’s energy output. “The forcings that drive long-term climate change,” concludes James Hansen, one of the pioneers of climate change science, “are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases, which are well measured, cause a strong positive forcing [warming]. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming.” And as if the physical factors were not challenging enough, the inherent complexity of the climate system will always be present to thwart attempts to predict future climate.

In view of climate’s complexity and the limitations of today’s climate simulations, one might expect that pronouncements as to human culpability for climate change would be made with considerable circumspection, especially pronouncements made in the name of the scientific community. So it was disturbing to many scientists that a summary report of the IPCC issued in 1996 contained the assertion that “the balance of evidence suggests a discernible climate change due to human activities.” The latest IPCC report (2001) goes even further, claiming that “there is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.” But most of this evidence comes from new computer simulations and does not satisfactorily address either the disparity in the empirical temperature record between surface and atmosphere or the large uncertainties in the contributions of aerosols and other factors. A report issued by the National Academy of Sciences in 2001 says this about the model simulations:

Because of the large and still uncertain level of natural variability inherent in the climate record and the uncertainties in the time histories of the various forcing agents (and presumably aerosols), a causal linkage between the buildup of greenhouse gases in the atmosphere and the observed climate changes during the 20th century cannot be unequivocally established. The fact that the magnitude of the observed warming is large in comparison to natural variability as simulated in climate models is suggestive of such a linkage, but it does not constitute proof of one because the model simulations could be deficient in natural variability on the decadal to century time scale.

These IPCC reports have been adopted as the centerpiece of most current popularizations of global warming in the media and in the environmental literature, and their political impact has been enormous. The 1996 report was the principal basis for government climate policy in most industrial countries, including the United States. The IPCC advised in the report that drastic reductions in the burning of fossil fuels would be required to avoid a disastrous global temperature increase. That advice was the driving force behind the adoption in 1997 of the Kyoto protocol to reduce carbon dioxide emissions in the near future.

In its original form, the protocol had many flaws. First, it exempted developing countries, including China, India, and Brazil, from the emission cutbacks; such countries are increasingly dependent on fossil fuels, and their current greenhouse gas emissions already exceed those of the developed countries. Second, it mandated short-term reductions in fossil fuel use to reach the emission targets without regard to the costs of achieving those targets. Forced cutbacks in fossil fuel use could have severe economic consequences for industrial countries (the protocol would require the United States to cut back its fossil fuel combustion by over 30 percent to reach the targeted reduction of carbon dioxide emissions by 2010), and even greater consequences for poor countries should they ultimately agree to be included in the emissions targets. The costs of the cutbacks would have to be paid up front, whereas the assumed benefits would come only many decades later. Third, the fossil fuel cutbacks mandated by the protocol are too small to be effective—averting, by one estimate, only 0.06ºC of global warming by 2050.

The Kyoto protocol was signed in 1997 by many industrial countries, including the United States, but to have legal status, it must be ratified by nations that together account for 55 percent of global greenhouse gas emissions. As of June 2002, the protocol had been ratified by 73 countries, including Japan and all 15 nations of the European Union. These countries are responsible, in all, for only 36 percent of emissions, but the 55 percent requirement may be met by Russia’s expected ratification. Nonetheless, the treaty is unlikely to have real force without ratification by the United States. The Bush administration opposes the treaty, on the grounds of its likely negative economic impact on America, and has thus far not sought Senate ratification. Even the Clinton administration did not seek ratification, despite its having signed the initial protocol, because it was aware that the U.S. Senate had unanimously adopted a resolution rejecting in principle any climate change treaty that does not include meaningful participation by developing countries.

With the United States retaining its lone dissent, 165 nations agreed in November 2001 to a modified version of Kyoto that would ease the task of reducing carbon dioxide emissions by allowing nations to trade their rights to emit carbon dioxide, and by giving nations credit for the expansion of forests and farmland, which soak up carbon dioxide from the atmosphere. A study by economist William Nordhaus in Science magazine (Nov. 9, 2001) finds that a Kyoto treaty modified along these lines would incur substantial costs, bring little progress toward its objective, and, because of the huge fund transfers that would result from the practice of emissions trading, stir political disputes. Nordhaus concludes that participation in the treaty would have cost the United States some $2.3 trillion over the coming decades—more than twice the combined cost to all other participants. It does not require sympathy with overall U.S. climate change policy to understand the nation’s reluctance to be so unequal a partner in the Kyoto enterprise.

Though the political controversy continues, the science has moved away from its earlier narrow focus on carbon dioxide as a predictor of global warming to an increasing realization that the world’s future climate is likely to be determined by a changing mix of complex and countervailing factors, many of which are not under human control and all of which are insufficiently understood. But regardless of the causes, we do know that Earth’s surface has warmed during the past century. Although we don’t know the extent to which it will warm in the future, or whether it will warm at all, we can’t help but ask a couple of critical questions: How much does global warming matter? What would be the consequences if the global average temperature did actually rise during the current century by, say, some 2ºC?

Some environmentalists have predicted dire consequences from the warming, including extremes of weather, the loss of agricultural productivity, a destructive rise in sea level, and the spread of diseases. Activists press for international commitments much stronger than the Kyoto protocol to reduce the combustion of fossil fuels, and they justify the measures as precautionary. Others counter that the social and economic impacts of forced reductions in fossil fuel use would be more serious than the effects of a temperature rise, which could be small, or even beneficial.

Although the debate over human impacts on climate probably won’t be resolved for decades, a case can be made for adopting a less alarmist view of a warmer world. In any event, the warmer world is already here. In the past 2,500 years, global temperatures have varied by more than 3ºC, and some of the changes have been much more abrupt than the gradual changes projected by the IPCC. During all of recorded history, humans have survived and prospered in climate zones far more different from one another than those that might result from the changes in global temperatures now being discussed.

Those who predict agricultural losses from a warmer climate have most likely got it backwards. Warm periods have historically benefited the development of civilization, and cold periods have been detrimental. For example, the Medieval Warm Period, from about 900 to 1300, facilitated the Viking settlement of Iceland and Greenland, whereas the subsequent Little Ice Age led to crop failures, famines, and disease. Even a small temperature increase brings a longer and more frost-free growing season—an advantage for many farmers, especially those in large, cold countries such as Russia and Canada. Agronomists know that the enrichment of atmospheric carbon dioxide stimulates plant growth and development in greenhouses; such enrichment at the global level might be expected to increase vegetative and biological productivity and water-use efficiency. Studies of the issue from an economic perspective have reached the same conclusion: that moderate global warming would most likely produce net economic benefits, especially for the agriculture and forestry sectors. Of course, such projections are subject to great uncertainty and cannot exclude the possibility that unexpected negative impacts would occur.

As for the concern that warmer temperatures would spread insect-borne diseases such as malaria, dengue fever, and yellow fever, there’s no solid evidence to support it. Although the spread of disease is a complex matter, the main carriers of these diseases—which were common in North America, western Europe, and Russia during the 19th century, when the world was colder than it is today—are most likely humans traveling the globe and insects traveling with people and goods. The strongest ally against future disease is surely not a cold climate but concerted improvement in regional insect control, water quality, and public health. As poverty recedes and people’s living conditions improve in the developing world, the level of disease, and its spread, can be expected to decrease. Paul Reiter, a specialist in insect-borne diseases, puts it this way:

Insect-borne diseases are not diseases of climate but of poverty. Whatever the climate, developing countries will remain at risk until they acquire window screens, air conditioning, modern medicine, and other amenities most Americans take for granted. As a matter of social policy, the best precaution is to improve living standards in general and health infrastructures in particular.

One of the direst (and most highly publicized) predictions of global warming theorists is that greenhouse gas warming will cause sea level to rise and that, as a result, many oceanic islands and lowland areas, such as Bangladesh, may be submerged. But in fact, sea level—which once was low enough to expose a land bridge between Siberia and Alaska—is rising now, and has been rising for thousands of years. Recent analyses suggest that sea level rose at a rate of about one to two centimeters per century (0.4 to 0.8 inch) over the past 3,000 years. Some studies have interpreted direct sea-level measurements made throughout the 20th century to show that the level is now rising at a much faster rate, about 10 to 25 centimeters per century (4 to 10 inches), but other studies conclude that the rate is much lower than that. To whatever extent sea-level rise may have accelerated, the change is thought to have taken place before the period of industrialization.

Before considering whether the ongoing sea-level rise has anything to do with human use of fossil fuels, let’s examine what science has to say about how global temperature change may relate to sea-level change. The matter is more complicated than it first appears. Water expands as it warms, which would contribute to rising sea level. But warming increases the evaporation of ocean water, which could increase the snowfall on the Arctic and Antarctic ice sheets, remove water from the ocean, and lower sea level. The relative importance of these two factors is not known.

We do know from studies of the West Antarctic Ice Sheet that it has been melting continuously since the last great ice age, about 20,000 years ago, and that sea level has been rising ever since. Continued melting of the ice sheet until the next ice age may be inevitable, in which case sea level would rise by 15 to 18 feet when the sheet was completely melted. Other mechanisms have been suggested for natural sea-level rise, including tectonic changes in the shape of the ocean basins. The theoretical computer climate models attribute most of the sea-level rise to thermal expansion of the oceans, and thus they predict that further global temperature increase (presumably from human activities) will accelerate the sea-level rise. But because these models cannot deal adequately with the totality of the natural phenomena involved, their predictions about sea-level rise should be viewed skeptically.

The natural causes of sea-level rise are part of Earth’s evolution. They have nothing to do with human activities, and there’s nothing that humans can do about them. Civilization has always adjusted to such changes, just as it has adjusted to earthquakes and other natural phenomena. This is not to say that adjusting to natural changes is not sometimes painful, but if there’s nothing we can do about certain natural phenomena, we do adjust to them, however painfully. Sea-level rise is, most likely, one of those phenomena over which humans have no control.

Some environmentalists claim that weather-related natural disasters have been increasing in frequency and severity, presumably as a result of human-caused global warming, but the record does not support their claims. On the contrary, several recent statistical studies have found that natural disasters—hurricanes, typhoons, tropical storms, floods, blizzards, wildfires, heat waves, and earthquakes—are not on the increase. The costs of losses from natural disasters are indeed rising, to the dismay of insurance companies and government emergency agencies, but that’s because people in affluent societies construct expensive properties in places vulnerable to natural hazards, such as coastlines, steep hills, and forested areas.

Because society has choices, we must ask what the likely effects would be, on the one hand, if people decided to adjust to climate change, regardless of its causes, and, on the other, if governments implemented drastic policies to attempt to lessen the presumed human contribution to the change. From an economic perspective at least, adjusting to the change would almost surely come out ahead. Several analyses have projected that the overall cost of the worst-case consequences of warming would be no more than about a two percent reduction in world output. Given that average per capita income will probably quadruple during the next century, the potential loss seems small indeed. A recent economic study emphasizing adaptation to climate change indicates that in the market economy of the United States the overall impacts of modest global warming are even likely to be beneficial rather than damaging, though the amount of net benefit would be small, about 0.2 percent of the economy. (We need always to keep in mind the statistical uncertainties inherent in such analyses; there are small probabilities that the benefits or costs could turn out to be much greater than or much less than the most probable outcomes.)

In contrast, the economic costs of governmental actions restricting the use of fossil fuels could be large indeed, as suggested by the Nordhaus study cited earlier on the costs of compliance with the Kyoto treaty. One U.S. government study proposed that a cost-effective way of bringing about fossil fuel reductions would be a combination of carbon taxes and international trading in emissions rights. Emissions rights trading was, in fact, included in the modified Kyoto agreement. But such a trading scheme would result in huge income transfers, as rich nations paid poor nations for emissions quotas that the latter would probably not have used anyway—and it’s not reasonable to assume that rich nations would be willing to do this.

Taking into account the large uncertainties in estimating the future growth of the world economy, and the corresponding growth in fossil fuel use, one group of economists puts the costs of greenhouse gas reduction in the neighborhood of one percent of world output, while another group puts it at around five percent of output. The costs would be considerably higher if large reductions were forced upon the global economy over a short time period, or if, as is likely, the most economically efficient schemes to bring about the reductions were not actually employed. Political economists Henry Jacoby, Ronald Prinn, and Richard Schmalensee put the matter bluntly: “It will be nearly impossible to slow climate warming appreciably without condemning much of the world to poverty, unless energy sources that emit little or no carbon dioxide become competitive with conventional fossil fuels.”

Some global warming has been under way for more than a century, at least partly from natural causes, and the world has been adjusting to it as it did to earlier climate changes. If human activity is finally judged to be adding to the natural warming, the amount of the addition is probably small, and society can adjust to that as well, at relatively low cost or even net benefit. But the industrial nations are not likely to carry out inefficient, Kyoto-type mandated reductions in fossil fuel use on the basis of so incomplete a scientific foundation as currently exists. The costs of so doing could well exceed the potential benefits. Far more effective would be policies and actions by the industrial countries to accelerate the development, in the near term, of technologies that utilize fossil fuels (and all resources) more efficiently and, in the longer term, of technologies that do not require the use of fossil fuels.

If climate science is to have any credibility in the future, its pursuit must be kept separate from global politics. The affluent nations should support research programs that improve the theoretical understanding of climate change, build an empirical database about factors that influence long-term climate change, and increase our understanding of short-term weather dynamics. Such research is fundamental to the greenhouse gas issue. But its rewards may be greater still, for it will also improve our ability to cope with extreme weather events such as hurricanes, tornadoes, and floods, whatever their causes.

Jack M. Hollander is professor emeritus of energy and resources at the University of California, Berkeley. His many books include The Energy-Environment Connection (1992) and The Real Environmental Crisis: Why Poverty, Not Affluence, Is the World’s Number One Enemy (2003), published by the University of California Press, from which this essay has been adapted. Copyright © 2003 by the Regents of the University of California.

Nice reply; I want to ponder it for the rest of the day (I've been working quite hard on my replies to you over the past couple of days, and I have other things to do). But in short:

OOPS I let a bit of an error creep in that Solar calculation of reply #100. You may wish to re-assess your opinion.

Albedo (0.3) is a measure of reflectivity of the earth, not absorption. Therefore the equations governing Solar forcing at the earth's surface must be changed somewhat using (1-albedo)=0.7 instead of albedo=0.3.

So on a second try with corrected figures and modified conclusions in red:

So let me ask you a pretty straightforward question: do you think that 0.75 C per 1 W m-2 of radiative forcing is a reasonable value for climate sensitivity?

hehe not-so-Easily checked:

The solar flux normally exhibits a p-p variation of 0.1% over an 11 year sunspot cycle(see: graph 40yr solar irradiation). That is 1.4wm^-2 (0.001*1366.5wm^-2)_p-p (i.e. 0.367 wm^-2 = [irradiance*(1-albedo)/4] *1.5 for back radiation from water vapor direct radiative forcing and other GHGs forcing manifested as a cyclic climate temperature variation).

Using this forcing and the GCM postulated feedbacks giving rise to climate sensitivity of 0.75^oC/wm^-2, we should expect to see a 0.28^oC p-p variation in global tropospheric temperatures with an 11 year solar cycle period. Observations indicate that the temperature oscillation is less than 0.05 C and it is difficult to detect.

This implies

1) the "feedbacks" postulated in the GCMs are manifested in the real world at fifth that level or
2) there is a long time constant damping radiative forcing effects on surface temperature.

Looking at longterm secular change in solar irradiation since 1800-1996AD removes shorterm damping effect. Long term change in solar effects has been about 4 times the magnitude of the sunspot related cycles, about 4.3wm^-2 overall change in Top Of Atmosphere(TOA) solar flux:

Hoyt, D. V. & Schatten, K. H.: The role of the sun in climate change. New York-Oxford, Oxford University Press, 1997, 61, 70, 86, 184,188,194, 214.
http://www.vision.net.au/~daly/solar/fig5.gif
Long Term changes in Solar Irradiance,Solanki &Figge, Page 7 figure 6
http://www.astro.phys.ethz.ch/papers/fligge/solspa_2.pdf

That gives us a change 4.3*0.7/4 = 0.7525 wm^-2 available for surface heating with an additional 50% re-radiated back to the surface from atmospheric water vapor(95%) & other GHGs(5%) yielding a total 1.129wm^-2.

The actual peak change in global surface temperature since 1900-1995 has been about 0.65^oC and has tracked with change in solar irradiation ±0.14^oC_peak.

Friis-Christensens E., Lassen K., 1994, Journal of Atmospheric and Terrestrial Physics 57(8), 835
http://web.dmi.dk/solar-terrestrial/space_weather/

http://www.astro.phys.ethz.ch/research/fligge/paleo_fig3_nf.html
http://solar-center.stanford.edu/sun-on-earth/glob-warm.html

Using the IPCC/GCM figure of 10 to 1 feedback, i.e. 0.75^oC/w * 1.129 wm^-2 = 0.84^oC_peak

That leaves nil for other factors for that period in comparison to the ±0.14^oC_peak. (i.e. 0.28^oC_p-p) curve fit error of the solar activity charts.

Seems we must attribute 100% of the 20th century change to changes in solar irradiation and net nil to all other driving changes using the UN/IPCC GCM average 0.75^oC/wm^-2 climate forcing.

Or, we seem to have a case of some missing in action climate feedback in the real world when testing global temperatures against radiative forcing from solar activity.

100% solar to nil% solar unrelated forcings leaves the IPCC/GCM 10 to 1 forcing multiplier an interesting number not allowing CO2 forced temperature change across the period from 1900 to 1995.

I had hoped to keep most of our discussion on this thread, so that we can reference it to others when other global warming topics arise on FR. Sadly, some of our give-and-take on the solar variability issue, particularly the Friis-Christensen results that you posted and to which I responded, has slopped into another thread. I'm going to attempt to bring it back here, but first: some pertinent new developments in the scientific evaluation of the Shaviv and Veizer paper.

It would appear that the scientists responding to Shaviv and Veizer are addressing a similar situation to what has occurred with the McIntyre and McKitrick "audit" paper on the Mann et al. research. In essence, a global-warming skeptical paper gets published, it gets promoted by the media and by global-warming-skeptical Web sites, and while the science is properly questioned in the give-and-take of published scientific journals (such as the Crowley and Berner article that I have referenced), a meta-debate ensues in the media in which the actual scientific results of a given publication are bent and stretched by various interest groups. That's the background for what I'm providing here.

Here are the links in chronological order, with relevant excerpts:

Galactic dust cooling Earth?

"They conclude that cosmic rays alone can account for 75% of the change in global climate during that period, and that less than half of the global warming seen since the beginning of the twentieth century is due to greenhouse gases."

Speculation on the influence of galactic cosmic rays on climate is scientifically untenable

"According to many climate scientists, the analyses made by Shaviv and Veizer and especially their conclusions are scientifically not well founded. The data of cosmic rays and temperature so far in the past are extremely uncertain. The reconstruction of cosmic rays is only based on about 50 meteorites, which are interpreted in a completelyvery very different way by other experts. In addition, the two curves only show a statistical correlation because the time scale of the cosmic data was arbitrarily stretched to obtain a match - the unadulterated data show no significant correlation."

continuing (emphasis added):

"Even if the analyses by Shaviv and Veizer were methodologically correct, it would yield no new insights about the ongoing climate change. The authors emphasize themselves that the correlation found is only valid for time scales of several million years. The current climate warming, however, occurs over a time scale of a few hundred years, for which completely different mechanisms are relevant. It is well known that on different time-scales different external forcing factors influence climate. Over millions of years this is, e.g., the shifting of continents, while over hundreds of thousands of years there are changes in orbital parameters. The latter e.g. initiate or terminate ice ages. But for time periods of years, decades or centuries these processes are irrelevant. Volcanic eruptions, changes in solar activity or the concentration of greenhouse gases, as well as internal oscillations of the climate system, are crucial here. Nevertheless, in someone german media reports (WirtschaftsBild, 6 Oct. 2003) the suggested cycle of Shaviv and Veizer has been cited as the cause of the warming of the past two decades. Even if this cycle were real, with 3 degrees C warming over 70 million years it would at most cause a warming of a few millionths of a degree over 250 years."

Discussion of the Statement on Shaviv & Veizer's paper

Dr. Nir Shaviv writing:

"> I carefully read the letter written by the cosigners and was quite bewildered by it. First, it is strange that they decided to hold a scientific debate by press releases. While I am sure that this debate is of interest to the general public, the nature of the medium allows them to bring forth accusations without actually presenting any supporting evidence. This is hardly a scientific approach, made even worse with general claims, such as "methodically very doubtful". To counter such a claim, we would have to show that all the steps we have taken were done carefully. Obviously I cannot condense about 75 journal pages of detailed analysis, published in 6 articles, and reviewed by 10 referees. I will, however, show how specific concerns are invalid."

Cosigners response:

"We agree that a proper scientific discussion needs to take place in the scientific journals, and to our knowledge one such journal article has been submitted and a second one is in preparation. As you know, such articles take many months to appear in print. We took the decision to make a public statement after careful consideration, because strong political claims were being made based on your publication. We would like to point out that you published a media release yourself on 12 August, titled "Global warming not a man-made phenomenon". This starts as follows: "Global warming will not be helped much by efforts to reduce carbon dioxide emission into the atmosphere, say two scientists who have studied the matter". You are cited as saying: "The operative significance of our research is that a significant reduction of the release of greenhouse gases will not significantly lower the global temperature, since only about a third of the warming over the past century should be attributed to man." Even if your scientific analysis were completely correct, your paper would have merely provided one intriguing piece of evidence pitted against many other studies that come to a different conclusion, and it would have been irresponsible to publish such a far-reaching statement in a press release, especially since your paper does not study 20th Century warming. After making such a strong claim about the "operative significance" of your work in the media, you can hardly be surprised that this will be scrutinised and criticised also in the public arena."

So that is the summary of the new developments regarding the Shaviv and Veizer paper. I think it's sufficient to say that the problem of time-scale and climatic setting make it extremely difficult to make direct inferences about how atmospheric CO2 concentrations affected past climates on multi-million year time-scales and relate them to how rising atmospheric CO2 concentrations may affect climate on decadal or century time-scales. And that's what we have to be concerned with now. I have attempted to show that the general view of the paleoclimatic community is that atmospheric CO2 concentrations have been a significant forcing factor over Phanerozoic time, which is at odds with your presentation of paleoclimate data.

So the next step is to address the influence of solar variability. I will start on that tomorrow, while conducting more research today.

So that is the summary of the new developments regarding the Shaviv and Veizer paper. I think it's sufficient to say that the problem of time-scale and climatic setting make it extremely difficult to make direct inferences about how atmospheric CO2 concentrations affected past climates on multi-million year time-scales and relate them to how rising atmospheric CO2 concentrations may affect climate on decadal or century time-scales.

And that's what we have to be concerned with now.

So lets bring things to the present and on a decadal basis shall we?

Shaviv and Veizer analyzed the impact on solar irradiation of the surface to be due to changes in cloud cover & albedo generally as a concequence of motion through the galaxy modulating impact of cosmic radiation.

This same effect has been characterized by many in the effect the solar wind has upon our climate through modulating a lesser level of cosmic radiation than the GRBs of Shaviv and Veizer.

Cosmic ray influence on the current climate are well represented in current solar studies, supporting Shaviv & Veizer's analysis what ever the "general view of the paleoclimatic community" may be:

SOLAR ACTIVITY:
A DOMINANT FACTOR IN CLIMATE DYNAMICS
Dr Theodor Landscheidt
Schroeter Institute for Research in Cycles of Solar Activity
Nova Scotia, Canada

4. Cosmic Radiation, Solar Wind, and Global Cloud Coverage
The most convincing argument yet, supporting a strong impact of the sun’s activity on climate change, is a direct connection between cloud coverage and cosmic rays, discovered by H. Svensmark and E. Friis-Christensen [111] in 1996. It is shown in Figure 6. Clouds have a hundred times stronger effect on weather and climate than carbon dioxide in the atmosphere. Even if the atmosphere’s CO2 content doubled, its effect would be cancelled out if the cloud cover expanded by 1%, as shown by H. E. Landsberg [53]. Svensmark’s and Friis-Christensen’s result is therefore of great importance. The thin curve in Figure 6 presents the monthly mean counting rates of neutrons measured by the ground-based monitor in Climax, Colorado (right scale). This is an indirect measure of the strength of galactic and solar cosmic rays. The thick curve plots the 12-month running average of the global cloud cover expressed as change in percent (left scale). It is based on homogeneous observations made by geostationary satellites over the oceans. The two curves show a close correlation. The correlation coefficient is
r = 0.95.
Short-range variations in the intensity of cosmic rays, caused by energetic solar eruptions, have the same effect, though shorter. The plot shows that strong cosmic rays go along with a larger cloud cover, whereas weak cosmic rays shrink the cloud cover. The global cloud coverage diminished from its peak at the end of 1986 to its bottom in the middle of 1990 by more than 3%. According to observations by V. Ramanathan, B. R. Barkstrom, and E. F. Harrison [91], clouds have a net cooling effect of -17 W/m² . Svensmark and Friis-Christensen [111] conclude from the diminution of this cooling effect between 1986 and 1990 that the solar irradiance has increased by about 1.5 W/m² within these three and a half years. A change of this order is quite remarkable, since the total radiative forcing by carbon dioxide accumulated since 1750 has been estimated by the IPCC not to go beyond 1.5 W/m² . This means that cosmic rays, strongly modulated by solar activity, achieve an effect within three and a half years for which the accumulation of carbon dioxide in the atmosphere needs centuries. This shows clearly to what extent the greenhouse effect has been overestimated in comparison with the solar contribution to climate change, which turns out to be the most important factor.
There is also a physical explanation of the effect: the secondary ions produced by the cosmic rays serve as condensation nuclei with hygroscopic properties that enhance the formation of clouds [4, 15, 23]. Meanwhile, H. Svensmark [112] has extended his investigation that now covers the interval 1980 to 1996. As before, the correlation between cloud cover and cosmic rays is very close. Indirect measurements of the intensity of cosmic rays, which register myons instead of neutrons, go back to 1937. When H. Svensmark [112] compared these data with global temperature in the Northern Hemisphere, he again found a strong correlation which indicates that the connection between cosmic rays, cloud cover, and global temperature is real.
The primary cause of the solar modulation of cosmic rays is not the level of sunspot activity, but the varying strength of the solar wind. This supersonic outflow of plasma originates in the very hot corona of the sun and carries ionized particles and magnetic field lines from the sun. While it is expanding towards the boundary of the solar system, cosmic ray particles interacting with it lose energy. When the solar wind blows heavily, cosmic rays are weak, and when the solar wind is in a lull, cosmic rays become strong. The highest velocities in the solar wind are caused by energetic solar eruptions and coronal holes. Strong eruptions (flares and eruptive prominences) avoid sunspot maxima and even occur close to sunspot minima. So sunspots are not a good indicator of solar wind strength [65]. As cosmic rays, which have such a strong impact on cloud cover, are strongly modulated by eruptional features of the sun’s activity, the solar contribution to climate change can no longer be considered negligible. This is all the more so as the already described changes in irradiance have an additional effect.
D. Rind and J. Overpeck [93] have shown that at least half of the rise in temperature since the end of the Little Ice Age can be attributed to the parallel rise in the sun’s irradiance. D. Hoyt and K. H. Schatten [39] judge their elaborate results as follows: “From the record, we believe the sun plays a major role in natural secular climatic changes on time scales of decades to centuries.". E. S. Posmentier, W. H. Soon, and S. L. Baliunas [88, 107] eventually derive from a model based on the same solar factors as in the Hoyt-Schatten-model that 78% of the rise in temperature between 1885 and 1987 can be explained by the sun’s varying irradiance. An additional statistical experiment corroborates this result, though it omits the Svensmark effect and other solar-terrestrial relationships which are independent from irradiance. There is not much room left for the anthropogenic greenhouse effect. H. N. Priem [90] aptly remarks:

“Recent studies show that solar variability rather than changing CO pressure is an important, probably the dominant climate forcing factor ... The current and anticipated fleet of spacecraft devoted to the study of solar and solar-terrestrial physics will therefore pobably prove to have more bearing on the understanding and forecasting of climate change than the orchestrated assessments by politically motivated international panels biased towards global warming exclusively by the enhanced greenhouse effect.”

I have attempted to show that the general view of the paleoclimatic community is that atmospheric CO2 concentrations have been a significant forcing factor over Phanerozoic time, which is at odds with your presentation of paleoclimate data.

And will remain at odds as long as solar factors, of necessity, have the dominant role in initiating changes in the climate.

For however you may try try to turn, the simple fact is that Temperature leads CO2 concentrations, demonstrating the lack of causality necessary for CO2 concentrations to be a dominant driver.

Global warming and global dioxide emission and concentration:
a Granger causality analysis
http://isi-eh.usc.es/trabajos/122_41_fullpaper.pdf

"We find, in opposition to previous studies, that there is no evidence of Granger causality from global carbon dioxide emission to global surface temperature. Further, we could not find robust empirical evidence for the causal nexus from global carbon dioxide concentration to global surface temperature."

And is why we find such a strong correlation as well as the obvious causual link between solar activity and surface temperature operating on the order of 10X temperature feedback( the Climate Sensitivity for radiant forcing as it is referred to by UN/IPCC modellers) over just the direct solar flux expressed as temperature through Stefan-Boltzmann:

http://web.dmi.dk/solar-terrestrial/space_weather/

The red curve illustrates the solar activity, which is generally increasing through an interval of 100 years, since the cycle lenght has decreased from around 11.5 years to less than 10 years. Within the same interval the Earth's average temperature as indicated by the blue curve has increased by approximately 0.7 degree C. Even the finer structures in the two curves have similar appearances.
(Reference: Friis-Christensen, E., and K. Lassen, Length of the solar cycle: An indicator of solar activity closely associated with climate, Science, 254, 698-700, 1991).

I'll provide a few starting points for discussion.

On the length of the solar cycle and the Earth's climate (PDF), a paper by Jon Egill Kristjansson, says this:

"Laut and Gundermann (1998a) questioned the methodology used by Lassen and Friis-Christensen (1995) and demonstrated that if fictitious temperature trends were added to the correct temperature series, then the correlations from Lassen and Friis-Christensen's method were equally convincing. Thus, according to Laut and Gundermann (1998a), the method cannot be used to unequivocally estimate the sun's contribution to the temperature variations. The same researchers (Laut and Gundermann 1998b) also pointed out inconsistencies in Lassen and Friis-Christensen's way of processing the temperature data. After removing these consistencies [sic], Laut and Gundermann (1998b) showed that the correlation became significantly stronger if the effects of anthropogenic greenhouse gases and aerosols were removed. These effects were calculated using a simple climate model. This suggests that the solar-cycle hypothesis actually supports rather than refutes the theory of an anthropogenic contribution to temperature changes.

Read the rest; summary sentence: "These findings appear to be in line with the conclusions of others such as Lean and Rind (1998), who believe that most of the warming since 1975 is human-induced."

What's Driving Climate Change in the 20th Century - Changes in Solar Radiation or the Buildup of Greenhouse Gases?

Excerpt (long):

"Climate models with realistic sensitivities simulate surface temperature changes of a few tenths of a degree C in response to plausible climate forcing due to changes in solar radiation over the past few hundred years. The simulations can account for two hundred years of surface temperature fluctuations prior to the industrial epoch (from 1600-1800). The solar-related warming in response to a solar forcing of 0.6 Wm-2 (from 1650 to the present) is calculated globally to be 0.45°C, but with strong regional signatures. Less than 0.25°C of this warming occurs from 1900-1990 when, for comparison, measured surface temperatures over this same period of time increased 0.6°C. In suggesting that the Sun's variability accounts for less than half the 0.6°C surface warming in the industrial period, the climate change model simulations are in good agreement with the pre-industrial empirical Sun-climate associations. A larger role for the Sun in explaining the observed climate warming over the twentieth century, is inconsistent with direct measurements of solar output, and with proxy evidence of solar variability during the pre-industrial era.

During the past two decades (1976-1996) direct observations of solar irradiance suggest negligible long-term solar forcing of climate. Over this observational period, solar radiation levels remained approximately constant, exhibiting no change during two successive solar cycle minima (1986 and 1996) while observed surface temperatures nevertheless increased by 0.2°C over the same period of time. Of course, even in the absence of long-term trends, climate variability may be associated with the 11-year irradiance cycle in ways implied by empirical associations, but not presently understood or accounted for in climate models.

Solar activity is presently at high levels relative to the historical record of the past 8,000 years. This suggests that future levels of solar radiation will probably be comparable to or less than present levels, and that future solar forcing will either be small, or negative relative to the climate forcing due to greenhouse gases, while projected concentrations of greenhouse gases continue to increase. Furthermore, solar activity levels during the past 8,000 years have ranged, typically, from low levels similar to the "Maunder Minimum" (a period of low solar irradiance circa 1650) to higher levels, on a par with the present. A warming on the order of 0.5°C that present scientific understanding and analyses attribute to this increase in solar forcing since 1650, possibly represents an upper limit to the observed surface temperature change attributable to solar radiation. Were solar activity to undergo another "Maunder Minimum" type event over the next 200 years, surface cooling would likely be 0.5°C or less, as a result. However, projections of future solar activity are exceedingly difficult for even one 11-year solar cycle, and are essentially impossible for the long-term. Ultimately, a more refined determination of the Sun's role in climate change requires a much longer record of measurements of solar radiation than the present meager 20-year database. Continuous, precise solar monitoring is crucial for the indefinite future. Improved understanding of the processes by which solar radiation interacts with the Earth is similarly essential to better specify climate's response to direct solar forcing of climate by fluctuations in solar radiation, and indirect solar forcing of climate via solar-related changes in atmospheric ozone.

The sun or mankind - Which is the strongest in climate change? (dated March 27 2003)

Opening paragraph:

"Climate researchers have been debating for some time whether the influence of changing solar activity or that of mankind exerts the greatest influence on climate change. The latest study from the Potsdam Institute for Climate Impact Research (PIK) shows that until the mid-19th century, climate changes are mainly traceable to changed sun activity and volcanic eruptions. Since that time, however, mankind has played the decisive role in climate change."

Excerpted paragraph:

"Since the start of industrialisation around 1850, increasing concentrations of greenhouse gases in the atmosphere have led to increasing warming. This warming is offset by the effect of deforestation, since the Earth's surface is lighter following deforestation and reflects more sunlight. The new study contains the surprising result that the Little Ice Age was prolonged in the 19th century by the effect of deforestation, although natural factors such as changes in solar activity and a reduction in volcanic activity would otherwise have led to warming earlier."

Lean, J., and D. Rind 1998. Climate forcing by changing solar radiation. J. Climate 11, 3069-3094

Full abstract:

"By how much does changing radiation from the sun influence the earth's climate, presently and in the recent past, compared with other matural and anthropogenic processes? Current knowledge of the amplitudes and timescales of solar radiative output variability needed to address this question is described from contemporary solar monitoring and historical reconstructions. The 17-yr observational database of space-based solar monitoring exhibits an 11-yr irradiance cycle with amplitude of about 0.1%. Larger amplitude solar total radiative output changes -- of 0.24% relative to present levels -- are estimated for the seventeenth-century Maunder Minimum by parameterizing the variability mechanisms identified for the 11-yr cycle, using proxies of solar and stellar variability. The 11- and 22-yr period evident in solar activity proxies appear in many climate and paleoclimate records, and some solar and climate time series correlate strongly over multidecadal and centennial timescales. These statistical relationships suggest a response of the climate system to the changing sun. The correlation of reconstructed solar irradiance and Northern Hemisphere (NH) surface temperature anomalies is 0.86 in the pre-industrial period from 1610 to 1800, implying a predominant solar influence. Extending this correlation to the present suggests that solar forcing may have contributed about half of the observed 0.55°C surface warming since 1900 and one-third of the warming since 1970. Climate model simulations using irradiance reconstructions provide a tool with which to identify potential physical mechanisms for these implied connections. An equilibrium simulation by the Goddard Institute for Space Studies GCM predicts an NH surface temperature change of 0.51°C for a 0.25% solar irradiance reduction, in general agreement with the preindustrial parameterization. But attributing a significant fraction of recent climate warming to solar forcing presents serious ambiguities about the impact of increasing greenhouse gas concentrations whose radiative forcing has been significantly larger than solar forcing over this time period. Present inability to adequately specify climate frocing by changing solar radiation has implications for policy making regarding anthropogenic global change, which must be detected against natural climate variability."

That should be enough for the first part of a point-counterpoint presentation. I haven't had a chance to look closely at your previous calculations yet; that will have to wait until next week.

Laut and Gundermann (1998b) showed that the correlation became significantly stronger if the effects of anthropogenic greenhouse gases and aerosols were removed.
***
. This suggests that the solar-cycle hypothesis actually supports rather than refutes the theory of an anthropogenic contribution to temperature changes.

LOL, nice doubletalk.

When one recognizes that temperature historically leads changes in CO2 concentration. The evidence of causation necessary for CO2 to be a substantive causative element of climate change is simply missing.

Global warming and global dioxide emission and concentration:
a Granger causality analysis
http://isi-eh.usc.es/trabajos/122_41_fullpaper.pdf

"We find, in opposition to previous studies, that there is no evidence of Granger causality from global carbon dioxide emission to global surface temperature. Further, we could not find robust empirical evidence for the causal nexus from global carbon dioxide concentration to global surface temperature.

"These findings appear to be in line with the conclusions of others such as Lean and Rind (1998), who believe that most of the warming since 1975 is human-induced."

An expression of "belief" hardly consititutes the necessary level of evidence that any such is true. The clear evidence says otherwise:

CO2-Temperature Correlations

"(1) correlation does not prove causation, (2) cause must precede effect, and (3) when attempting to evaluate claims of causal relationships between different parameters, it is important to have as much data as possible in order to weed out spurious correlations.

***

Consider, for example, the study of Fischer et al. (1999), who examined trends of atmospheric CO2 and air temperature derived from Antarctic ice core data that extended back in time a quarter of a million years. Over this extended period, the three most dramatic warming events experienced on earth were those associated with the terminations of the last three ice ages; and for each of these climatic transitions, earth's air temperature rose well in advance of any increase in atmospheric CO2. In fact, the air's CO2 content did not begin to rise until 400 to 1,000 years after the planet began to warm. Such findings have been corroborated by Mudelsee (2001), who examined the leads/lags of atmospheric CO2 concentration and air temperature over an even longer time period, finding that variations in atmospheric CO2 concentration lagged behind variations in air temperature by 1,300 to 5,000 years over the past 420,000 years."

[ see also: Indermuhle et al. (2000), Monnin et al. (2001), Yokoyama et al. (2000), Clark and Mix (2000) ]

"Other studies periodically demonstrate a complete uncoupling of CO2 and temperature "

[see: Petit et al. (1999), Staufer et al. (1998), Cheddadi et al., (1998), Raymo et al., 1998, Pagani et al. (1999), Pearson and Palmer (1999), Pearson and Palmer, (2000) ]

"Considered in their entirety, these several results present a truly chaotic picture with respect to any possible effect that variations in atmospheric CO2 concentration may have on global temperature. Clearly, atmospheric CO2 is not the all-important driver of global climate change the climate alarmists make it out to be.

"Climate models with realistic sensitivities simulate surface temperature changes of a few tenths of a degree C in response to plausible climate forcing due to changes in solar radiation over the past few hundred years.

What precisely are these "realistic sensitivities? You quote (0.75C/wm^-2) as the number for Climate Sensitivity derived from these climate models.

"Present estimates of climate sensitivity rest entirely on climate model calculations."
Stephen E Schwartz
Brookhaven National Laboratory
PDF 2/12/2003

of this warming occurs from 1900-1990 when, for comparison, measured surface temperatures over this same period of time increased 0.6°C.

The 0.6°C of the 1900-1990 period must of necessity be due to Solar Activity, For as I have amply shown in reply #105 above, going so far as to use the IPCC/GCM Climate Sensitivity value you apparently accept, i.e. 0.75^oC/wm^-2.

Using the UN/IPCC Climate Sensitivity of 0.75^oC/wm^-2results in a temperature change due to surface irradiation 1890-1995, comparable to the change in surface temperatures of that period, 0.75^oC/wm^-2 * 1.129 wm^-2 = 0.84^oC_p-p:

Top of Atmosphere Solar Irradiation left(dottedline),
Relative Temperature (solidline, 1750 base) right scale.
Hoyt and Schatten 1997

With nil residual temperature left over as a role for CO2, and says the (0.75C/wm^-2) UN/IPCC climate Sensitivity (feedback) iif we assign 100% of the change in temperatures to Solar Activity. And grossly too high if we don't.

Sorry I don't buy the anthropogenic CO2/Global Warming baloney and neither should the American public.

Sorry for the delay in responding. I had to take a mental break, and I also had to recover somewhat from a very persistent respiratory virus.

I took a look at the "Granger causality" paper. One of the overriding concepts that can be gleaned from the IPCC reports is the complexity of the problem of extracting the CO2 contribution to warming in the context of climate variability. (This has a bearing on the Laut and Gundermann result, which I will comment on later.)

It therefore seems rather simplistic to think that statistically, one can test to see if CO2 has a clearly-defined causal relationship to global temperature variability, given that numerous researchers are on record as indicating there is no such simple causal relationship. Thus, I expect that Triacca's paper has had little impact on the subject.

(The following addresses the section in the post being replied to (112), beginning "CO2-temperature Correlations".)

There is far more interesting material to examine. As noted several times previously, there is no dispute about the fact that when the Earth warms due to (apparently) astronomical factors such as Milankovitch forcing, CO2 responds to the warming by increasing. This was noted by Hansen in the cited article, who then emphasizes that the CO2 concentration contributes to the maintenance/ persistence of either warm or cold conditions. I've said the same thing in our discussions. What is particularly noteworthy about the CO2 concentration record over the past 420,000 years is that it did not exceed 280 ppmv: and now that the concentration is 80+ ppmv above that apparently natural bound, and rising, the consequences of this are unpredictable and modeling is one way of examining the potential effects.

What would be needed to test this? What about an atmospheric increase during a period devoid of any other major climate forcing factors? And we've also discussed this; posts 94 and this thread:

Evidence of global warming in the past supports greenhouse theory

Regarding this event, I'll point out something important which I have not noted previously. The time-scale for the event is a duration of ~100,000 years. It cannot be determined how quickly (on time-scales of centuries) how rapidly the Earth's climate responded with a temperature increase to the forcing of the released GHGs. According to the related articles, radiative forcing could have ranged between 1.5-13.3 W m-2, centering on about 3 W m-2, and the global temperature increase was about 5 degrees C. (Which is a climate sensitivity of 1.6, not 0.75, but this was a different climate regime than present-day.)

Also note that the GHG of primary interest is methane, not CO2. And methane is better by about 4x in terms of longwave radiation absorption. Nevertheless, it's a good test, as it indicates that there will be a climate response to greenhouse-gas induced changes in radiative forcing. You have been consistently arguing against any significant GHG radiative forcing or measurable temperature response.

HAVING SAID ALL THAT, now I can examine some of the solar activity information.

Let's look at Hoyt and Schatten. While I credit the output of your calculations, I can't say the same for the input:

Figure 6.5: Reconstructions of total solar irradiance (TSI) by Lean et al. (1995, solid red curve), Hoyt and Schatten (1993, data updated by the authors to 1999, solid black curve), Solanki and Fligge (1998, dotted blue curves), and Lockwood and Stamper (1999, heavy dash-dot green curve); the grey curve shows group sunspot numbers (Hoyt and Schatten, 1998) scaled to Nimbus-7 observations for 1979 to 1993.

So Hoyt and Schatten's reconstruction shows a maximum range of variability of about 4 W m-2 TSI in the 20th century, while three other groups show a maximum range of variability of about 2 W m-2. Very interesting. If you then note that Hoyt and Schatten (and others) indicate that they think that the Sun is responsible for all of the observed 20th century warming, and that the other groups (such as Lean and Rind, whom you maligned unfairly with your characterization of their research) say that it's about half -- then the source of the discrepancy would appear to be the difference in the solar variability reconstructions.

(It's somewhat amusing to me that many of your references and supporting arguments come from the CO2science Web site. They are presenting their skeptical case, and it's obviously a one-sided presentation. When one investigates what other data and information can be assessed, it is clear that the CO2science Web site is excluding quite a bit.)

Now I will ask you: what happens if you amend your calculations with only a 2 W m-2 change in solar variability, rather than 4? Is there then "room" for the influence of GHGs, particularly in the latter part of the 20th century (and early 21st) when there is no evidence of a particularly large increase in TSI since 1979?

Now here's what the IPCC has to say in conclusion about solar variability:

The estimate for solar radiative forcing since 1750 of 0.3 Wm-2, shown in Figure 6.6, is based on the values in Figure 6.5 (taking the 11-year cycle minimum values in 1744 and 1996). Clearly the starting date of 1750 (chosen for the date of the pre-industrial atmosphere in Figure 6.6) is crucial here: a choice of 1700 would give values about twice as large; a choice of 1776 would give smaller values (particularly using the Hoyt and Schatten series). The range of 0.1 to 0.5 Wm-2 given in Figure 6.6 is based on the variability of the series, the differences between the reconstructions and uncertainties concerning stratospheric adjustment (see Section 6.11.2.1). However, because of the large uncertainty in the absolute value of TSI and the reconstruction methods our assessment of the "level of scientific understanding" is "very low".

SO: to use one group's numbers as the last word on the influence of solar variability is dangerous; to make a conclusion that the solar variability issue is settled would be wrong. The Sun could still end up being a more dominant forcing factor than the IPCC (and the position that I am defending) indicate. But the issue is not by any means fully clarified.

Regarding Laut and Gundermann's result:

Here's their abstract:

"Since the discovery of a striking correlation between 1-2-2-2-1 filtered solar cycle lengths and the 11-year running average of Northern Hemisphere land air temperatures there have been widespread speculations as to whether these findings would rule out any significant contributions to global warming from the enhanced concentrations of greenhouse gases. The "solar hypothesis" (as we will term this assumption) claims that solar activity causes a significant component of the global mean temperature to vary in phase opposite to the filtered solar cycle lengths. In an earlier paper we have demonstrated that for data covering the period 1860-1980 the solar hypothesis does not rule out any significant contribution from man-made greenhouse gases and sulphate aerosols. The present analysis goes a step further. We analyse the period 1579-1987 and find that the solar hypothesis - instead of contradicting - appears to support the assumption of a significant warming due to human activities. We have tentatively "corrected" the historical Northern Hemisphere land air temperature anomalies by removing the assumed effects of human activities. These are represented by Northern Hemisphere land air temperature anomalies calculated as the contributions from man-made greenhouse gases and sulphate aerosols by using an upwelling diffusion-energy balance model similar to the model of Wigley and Raper employed in the Second Assessment Report of The Intergovernmental Panel on Climate Change. It turns out that the agreement of the filtered solar cycle lengths with the "corrected" temperature anomalies is substantially better than with the historical anomalies, with the mean square deviation reduced by 36 % for a climate sensitivity of 2.5 oC, the central value of the IPCC assessment, and by 43 % for the best-fit value of 1.7 C. Therefore our findings support a total reversal of the common assumption that a verification of the solar hypothesis would challenge the IPCC assessment of man-made global warming." (emphasis mine)

The way I read this: when you take out the temperature effects of GHGs and aerosols, the remaining temperature signal is better correlated with solar variability than when all of the forcing factor contributions are included. I.e., the Sun is part of what's happening, but by removing the other contributing causes is the relationship between temperature and solar variability becomes clearer. This means that the current (late 19th - early 21st century) pattern of climate variability results from a combination of GHG forcing, aerosol forcing, and solar forcing. If it is true that there has not been significant solar variability since 1979, then the observed warming is predominantly caused by other forcing factors.

Now I will ask you: what happens if you amend your calculations with only a 2 W m-2 change in solar variability, rather than 4?

Halving the deviation of incident radiant flux would only change the imperical determination of the magnitude of the solar-wind component necessary to account for that faction of solar activity that occurs in conjunction with changes in radiant flux.

Is there then "room" for the influence of GHGs, particularly in the latter part of the 20th century (and early 21st) when there is no evidence of a particularly large increase in TSI since 1979?

No because a linear regession of solar activity alone (direct irradiation and the solar wind effect on cloud cover through modulation of gamma radiation flux) accounts for the total change in temperature.

Top of Atmosphere Solar Irradiation left(dottedline),
Relative Temperature (solidline, 1750 base) right scale.
Hoyt and Schatten 1997

The point is that direct irradiation by the sun is not the sole operative factor. If it were we would only see a .1^oC change with solar activity.

Solar activity is a function of both intensity of solar wind (affecting cloud cover) and direct irradiation.

The variation in direct irradiation incident with the surface from direct irradiation is modulated with a correlated change in cloud cover induced through variation of the solar wind affecting gamma radiation intensity.

Clouds have a hundred times stronger effect on weather and climate than carbon dioxide in the atmosphere. Even if the atmosphere’s CO2 content doubled, its effect would be cancelled out if the cloud cover expanded by 1%, as shown by H. E. Landsberg: Man-made climatic changes. In: Proceedings of the symposium on physical and dynamic climatology of the World Meteorological Organization 347 (1974), 262.

Cosmic ray flux modulated by solar activity, from Svensmark & Friis-Christensen:

The thin curve in Figure 6 presents the monthly mean counting rates of neutrons measured by the ground-based monitor in Climax, Colorado (right scale). This is an indirect measure of the strength of galactic and solar cosmic rays. The thick curve plots the 12-month running average of the global cloud cover expressed as change in percent (left scale). It is based on homogeneous observations made by geostationary satellites over the oceans. The two curves show a close correlation. The correlation coefficient is
r = 0.95.

CO₂ as a GHG simply has only minimal connection with any feedback of the like of Solar Activity and cloud cover. That is especially true, concidering CO₂'s minority status as a GHG on earth as compared to water vapor comprising 95% of the greenhouse effect on the earth's atmosphere.

http://www.clearlight.com/~mhieb/WVFossils/greenhouse_data.html
Anthropogenic (man-made) Contribution to the "Greenhouse
Effect," expressed as % of Total (water vapor INCLUDED)

Based on concentrations (ppb) adjusted for heat retention characteristics % of All Greenhouse Gases
% Natural

% Man-made

Water vapor 95.000%
94.999%
0.001%

Carbon Dioxide (CO2) 3.618%
3.502%
0.117%

Methane (CH4) 0.360%
0.294%
0.066%

Nitrous Oxide (N2O) 0.950%
0.903%
0.047%

Misc. gases ( CFC's, etc.) 0.072%
0.025%
0.047%

Total 100.00%
99.72
0.28%

Now here's what the IPCC has to say in conclusion about solar variability:

The estimate for solar radiative forcing since 1750 of 0.3 Wm-2, shown in Figure 6.6, is based on the values in Figure 6.5 (taking the 11-year cycle minimum values in 1744 and 1996).

Since solar activity is not a function of radiant flux alone, and includes the effect of solar wind as well as long term (decadal & secular) variations. Statements concerning the 11 year cycle alone is not germane and was discarded as the main source of variation per our calculations:

Refer reply #105:

"The solar flux normally exhibits a p-p variation of 0.1% over an 11 year sunspot cycle(see: graph 40yr solar irradiation). That is 1.4wm^-2 (0.001*1366.5wm^-2)_p-p (i.e. 0.367 wm^-2 = [irradiance*(1-albedo)/4] *1.5 for back radiation from water vapor direct radiative forcing and other GHGs forcing manifested as a cyclic climate temperature variation).
Using this forcing and the GCM postulated feedbacks giving rise to climate sensitivity of 0.75^oC/wm^-2, we should expect to see a 0.28^oC p-p variation in global tropospheric temperatures with an 11 year solar cycle period. Observations indicate that the temperature oscillation is less than 0.05 C and it is difficult to detect.
This implies

1) the "feedbacks" postulated in the GCMs are manifested in the real world at fifth that level or
2) there is a long time constant damping radiative forcing effects on surface temperature."

to use one group's numbers as the last word on the influence of solar variability is dangerous; to make a conclusion that the solar variability issue is settled would be wrong. The Sun could still end up being a more dominant forcing factor than the IPCC (and the position that I am defending) indicate. But the issue is not by any means fully clarified.

Which is precisely why basing world economic & political policies on UN/IPCC storylines,

http://www.pacificresearch.org/pub/cap/2003/cap_03-02-20.html

"The Economist, which provides the best environmental reporting of any major news source, carried a small story last week about a simple methodological error in the latest U.N. global warming report that has huge implications. The article, "Hot Potato: The Intergovernmental Panel on Climate Change (IPCC) Had Better Check Its Calculations" (February 15 print edition), reviews the work of two Australian statisticians who note an anomaly in the way the IPCC estimated world carbon dioxide emissions for the 21st century."
......
"The IPCC's method has the effect of vastly overestimating future economic growth (and, therefore, CO2 emissions) by developing nations. The fine print of the IPCC's projections, for example, calls for the real per-capita incomes of Argentina, South Africa, Algeria, Turkey, and even North Korea to surpass real per-capita income in the United States by the end of the century. Algeria? North Korea? The IPCC must be inhaling its own emissions to believe this."

and their GC Model outputs is folly in the highest degree:

Global Warming Score Card

As our "Greenhouse Warming Scorecard" shows below, the IPCC models are false in many ways. Let's just highlight a few things where the models disagree with observations:

1) The models predict the recent warming due to greenhouse gases should occur equally during the day and night. Observations show nearly all the warming is occurring at night ***
2) Several models now published have model global temperatures and measured temperatures paralleling each other over time remarkably well. These models "explain" the warming to 1940 by anthropogenic carbon dioxide, the cooling from 1940 to 1970 by anthropogenic sulfate aerosols, and resumed warming from 1970 to the present by the anthropogenic carbon dioxide warming again become dominant. These models make an implicit unstated (and frankly bizarre) assumption that without these anthropogenic forcings, the natural climate would have been perfectly flat for 100+ years. No century has ever had such a stable climate, but for the anthropogenic forcing models to work, this assumption must be made. ***
3) The models predict that cloud cover should be decreasing, and, in fact, such a decrease is crucial to amplify the greenhouse effect so it becomes the "enhanced" greenhouse effect. All measurements show cloud cover is increasing. ***
4) The models predict that the global annual cycle of temperatures should have decreased by 0.5 to 1.1 C during this century if greenhouse gases are forcing climate change. Measurements show only a 0.1 C decrease, thus invalidating the greenhouse warming hypothesis.
5) The models attribute the cooling from about 1940 to 1970 to sulfate aerosols. The quantity of aerosols they used are not based upon measurements, but are themselves model results. One prediction of this model is a maximum amount of aerosols in central Europe. Observations of atmospheric transmission in Davos Switzerland, right in the middle of the region where the model maximum in sulfates presumably existed, show no change in atmospheric transmission, contrary to the IPCC predictions. Observations in Belgium, Ireland, and other locations also falsify the IPCC modeled amounts of sulfate aerosols.
6) The models predict sulfate aerosols will cause a cooling forcing of 0.6 to 0.9 W/m². Actual field measurements of the scattering properties of sulfate aerosols show that the models overestimate their cooling potential by a factor of 3 to 5. These measurements falsify the model's radiative treatment of sulfates and show that the cooling from 1940 to 1970 cannot be attributed to anthropogenic aerosols.
7) The models neglect to include soot particles, which warm. Measurements show that the warming by soot offsets any cooling by sulfates, particularly in urban regions.
8) The models predict a warming of about 0.35 C per decade in the mid-troposphere. Two satellites (MSU and TOVS) and radiosondes show a cooling, thus falsifying the IPCC models. [measures since this statement still only show +.07C per decade (1/5th that of the IPCC models)]
9) The models predict a warming of 1.0 to 3.0 C should have occurred in the polar regions between 1940 and now. Thermometer measurements show a cooling over this time period for the arctic as a whole, thus falsifying the models. ***
10) The models predict the phase of the global annual cycle of temperatures should have shifted by minus 1.7 days in the twentieth century. Observations show a phase shift of +0.8 days, opposite in sign to what the models predict, thus falsifying the IPCC models.
11) The models predict a 0.50 cm/yr rise in sea level. The TOPEX/POSEIDEN observations show a 0.06 cm/yr rise, thus falsifying the IPCC models.

These eleven tests all falsify the IPCC climate models. There are many additional ways the models fail, some of which are covered in the scorecard below. A common feature of these falsifications is that the models tend to overestimate signals by a factor of 3 to 10. This suggests the predicted warming of 2.5 C for a doubling of greenhouse gases will really be between 0.25 and 0.8 C.

Seems to me even you admit there there is room for substantial doubt as to the magnitude or even sign of any effect "human created" CO2, Methane etc. may have on our Climate future.

and it is premature to state either a) solar variability is well-enough quantified to say that it only partially contributes to the observed warming trend, or b) solar variability is well-enough quantified that it is clearly the overriding cause of the observed warming trend.

And is substantially more invalid, to presume anthropogentic CO₂ to be the prime driver in global climate change on earth as an axiom built into the UN/IPCC GCM's with a total lack of emperical evidence to support its role as such:

CO₂-Temperature Correlations

"(1) correlation does not prove causation, (2) cause must precede effect, and (3) when attempting to evaluate claims of causal relationships between different parameters, it is important to have as much data as possible in order to weed out spurious correlations.

***

Consider, for example, the study of Fischer et al. (1999), who examined trends of atmospheric CO2 and air temperature derived from Antarctic ice core data that extended back in time a quarter of a million years. Over this extended period, the three most dramatic warming events experienced on earth were those associated with the terminations of the last three ice ages; and for each of these climatic transitions, earth's air temperature rose well in advance of any increase in atmospheric CO2. In fact, the air's CO2 content did not begin to rise until 400 to 1,000 years after the planet began to warm. Such findings have been corroborated by Mudelsee (2001), who examined the leads/lags of atmospheric CO2 concentration and air temperature over an even longer time period, finding that variations in atmospheric CO2 concentration lagged behind variations in air temperature by 1,300 to 5,000 years over the past 420,000 years."

[ see also: Indermuhle et al. (2000), Monnin et al. (2001), Yokoyama et al. (2000), Clark and Mix (2000) ]

"Other studies periodically demonstrate a complete uncoupling of CO2 and temperature "

[see: Petit et al. (1999), Staufer et al. (1998), Cheddadi et al., (1998), Raymo et al., 1998, Pagani et al. (1999), Pearson and Palmer (1999), Pearson and Palmer, (2000) ]

"Considered in their entirety, these several results present a truly chaotic picture with respect to any possible effect that variations in atmospheric CO2 concentration may have on global temperature. Clearly, atmospheric CO2 is not the all-important driver of global climate change the climate alarmists make it out to be."

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Based on concentrations (ppb) adjusted for heat retention characteristics	% of All Greenhouse Gases	% Natural	% Man-made
Water vapor	95.000%	94.999%	0.001%
Carbon Dioxide (CO2)	3.618%	3.502%	0.117%
Methane (CH4)	0.360%	0.294%	0.066%
Nitrous Oxide (N2O)	0.950%	0.903%	0.047%
Misc. gases ( CFC's, etc.)	0.072%	0.025%	0.047%
Total	100.00%	99.72	0.28%