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.

I would trust the man who is not being paid, he has nothing to lose by telling the truth and nothing to gain by distorting the truth to please his politically motivated patrons.

I will grant that the opinions of informed individuals on subjects that lie outside of their area of expertise can be valuable, if those individuals are truly well-informed. However, the ability to be "truly" well-informed on a particular topic becomes more difficult as the complexity of the topic increases. An uninformed opinion, or an opinion based only a skewed awareness of the information that is relevant to the topic, is not very valuable. If uninformed or skewed opinions are presented as being equivalent to well-informed opinions, then the validity of any conclusions that can be drawn about the topic from a compilation of such opinions is marginal.

Let's break this down to a very simple example (which happened to me recently). You're driving through an unfamiliar town trying to find the local post office. You can ask anybody you see how to get there. You happen to spot a mail carrier delivering mail to the businesses along a central street in the town.

Would you prefer to ask the mail carrier for directions to the post office, or just anyone who is walking on the street? (You can assume that most people walking on the street are local and might know how to get to the post office.) Explain your answer.

Extend this a bit. Just imagine that you can survey two groups in the town to get directions to the post office from a given location. One group is made up exclusively of the town's mail carriers; the other is a random group of town citizens. When you examine the two sets of responses, would you expect the quality of the responses from the mail carriers to be generally better than the quality of responses from the random group of citizens?

Now let's go one step further. Imagine that instead of mail carriers, you have one group made of citizens of the town, and another group composed of citizens from the state that the town is located in. The only criterion for inclusion in the latter group is that the citizens can locate the town on a map of the state.

Which of these groups will likely provide the better set of directions to the post office?

Who do you think might have a better understanding of global warming -- a meteorologist or a microbiologist? Now, the meteorologist could be a dunce and the microbiologist a brilliant person who knows a lot about a lot of things (including global warming): but without knowing anything other than their profession, who would you choose?

There simply is not sufficient evidence to support the viewpoint that significant danger is posed to the planet by mankind's meager contribution to "greenhouse gasses" and supporting a radical change in our economy.

All I can find, that holds up under close scrutiny, seems to support that view.

For purposes of clarity and a reality check against the UN/IPCC model outputs, the following is a summary of my position concerning the relationship between CO2 concentration and global surface temperatures.

I would appreaciate any evaluation or correction you may care to provide.

Note that the doubling of CO2 used here as a measurement basis is merely for convience of discussion consistent with terms used by the IPCC. It does not represent what I believe to be a reasonable projection of changes in the CO2 concentration for the future century.

From observed data:

0.27^oC change in Earth's surface temperature for CO₂ doubling is depicted in the following graphic:

The upper horizontal redline represents a temperature of 22.8^oC at the chart Cambrian CO₂ peak of 7000ppm.

The second and descending redline is a rough approximation of the average peak temperatures connecting similar conditions of albedo and near constant climate factors, the downtrending redline terminates at approximately 21.6^oC and today's 320ppm CO2 concentration.

Which appears to merely be a confirmation of what can determined from first principles:

Given:

The temperature of the Earth's surface with an atmosphere is 288^oK (+15^oC).
and the blackbody temperature of the Earth without atmosphere at 255^oK (-18^oC)

One may apply the Stefan-Boltzman relation:

E=sT⁴
where:
E = total amount of radiation emitted by an object per square meter (Watts m^-2)
s is a constant called the Stefan-Boltzman constant = 5.67 x 10^-8 Watts m^-2 K^-4
T is the temperature of the object in K

to determine the total GHG radiative forcing necessary to maintain the atmosphere/surface greenhouse temperature at the current 288^oK surface temperature of the earth.

Under constant albedo conditions (CO2 does not contribute to earth's albedo) The total flux at the Earth's troposphere/surface system due to greenhouse factors is:

Flux (E₂₈₈) at the Earth's surface with atmosphere               = 5.67*10^-8(288^oK)⁴ = 390.08 w/m²
Blackbody flux (E₂₅₅) without atmosphere                          = 5.67*10^-8(255^oK)⁴ = 279.74 w/m²==================================================================
                                                                                                            difference = 110.34 w/m²

The (natural + anthropogenic) CO2 contribution is 3.6% of atmospheric greenhouse warming. When expressed in terms of overall radiative forcing acting on both atmosphere and surface all radiative flux associated with CO2 must, of necessity, be:

0.036*110.34 w/m² = 3.97 w/m²

However, CO2 IR flux at surface temperature from CO2 concentrations in the atmosphere is less than half that total CO2 contribution of 3.97w/m²to the system, (at least half of the CO2 IR flux is radiated and/or scattered by clouds & dust upward to be lost to space and atmospheric heating rather than contributing towards surface warming.)

Re-cycling of Infra-Red Energy

According to Dr Hugh Ellsaesser's IPCC submission, "The direct increase in radiative heating of the lower atmosphere (tropopause level) due to doubling CO2 is 4 wm^-2. At the surface it is 0.5 - 1.5 wm^-2". Schlesinger & Mitchell (1985), estimated this surface flux at 2 wm^-2. Thus, depending on the model, or modeler, the estimates for increased surface flux following a CO2 doubling, varies between +0.5 and +2 wm^-2. An above-averaged figure of +1.5 wm^-2will be assumed here for purposes of analysis and comparison.

Doubling the atmospheric CO2 concentration can only add 1.5w/m² at the surface for a total surface radiative forcing of

390.08+3.97 = 391.58w/m2

Giving us

(391.58/5.67*10^-8)^0.25-288^oK = 0.277^oK (C)increase in surface temperature for doubling of atmospheric CO2 concentration.

A result well within any reasonable expectation of our rough graphic estimate of 0.27oC associated with CO2 doubling derived from the paleo CO2-temperature record in my prior replies.

OK. This will be a shorter reply than I had planned; I have numerous activities pressing on me both professional and personal (foremost among them a birthday party for toddler twins) as well as coping with a nasty respiratory infection that just will not let go. Let this provide some talking points for next week.

Number 1: is the derivation of average global temperature something that you did as an analysis, or is it taken from an accessible publication? I.e., is there any justification other than your own ideas for your running a trendline through peak global temperatures to show the correspondence of CO2 and temperature? The main reason that I'm asking this is that I will contrast it with the CO2 + sun forcing plot that is provided in the aforementioned Crowley and Berner paper. Radiative forcing varies from a minimum value of -13.5 W m-2 to a maximum of 10+ W m-2 over the Phanerozoic. On the same plot they provide a scaled del oxygen 18 temperature data from deep-sea sediments over the past 100 million years, which shows a temperature decrease from the Cretaceous of about 4.5 C. (The decrease into the Holocene is right on the edge of the graph.) The latter data agrees with what we see on the right side of your graph.

Sooo... while Crowley and Berner show major variations in net forcing due to CO2 variability, your analysis does not. I do not know how to reconcile this discrepancy. In essence, the radiative forcing during glacial periods is shown as roughly 20 W/m -2 compared to non-glacial periods.

Your analysis indicates that for a 20 W m-2 forcing difference, which corresponds to a 10 deg C change in global temperature over the same time period, only 1 deg C of that change is due to CO2? That's the BIG discrepancy of which I speak. Feel free to explain; please concentrate on this point.

Two short points. Crowley and Berner say this directly about the Ordovician glaciation:

"In the case of the relatively short-lived Ordovician glaciation (about 440 Ma) which occurred at a time of high net radiative forcing, climate models suggest that the unusual continental configuration of Gondwanaland (essentially a large landmass tangent to the South Pole) could result in conditions where high CO2 and glaciation can co-exist. A brief negative excursion of CO2 at this time may also have contributed to this glaciation. *" (Latter text also refers to other processes that could have affected ocean heat transport.)

* not very large, according to the graph

Last point, regarding the temperature and CO2 variability over the past 420,000 years. It is indeed true that temperature increase preceded CO2 rise each time. This is fairly obvious, and likely primarily due to release of CO2 from a warmer ocean. The current situation, however, is without precedent, as the CO2 concentration has exceeded the boundary conditions for atmospheric CO2 concentrations over that interval by about 80 ppmv. This is why predictions of what will happen are difficult to compare to the paleoclimate record.

Next week I want to re-examine the relationship between radiative forcing and climate sensitivity, and determine if what I mean by "climate sensitivity" is the same or different than what you mean by it.

Sorry for the necessary brevity of this response; we will continue next week.

is the derivation of average global temperature something that you did as an analysis,

http://www.doc.mmu.ac.uk/aric/eae/Climate/Older/Global_Climate.html

"Today, the global average surface temperature is about 15°C. This is 33°C warmer than the average surface temperature of the moon, which is about the same distance from the Sun as the Earth. The moon, of course, does not have an atmosphere, and therefore no greenhouse gases to trap extra heat."

Though any value in the range from 13.38 through 14.4^oC for yr 2000 might be more precise refer to chart: http://carto.eu.org/article2480.html would provide a more precise calculation.

Just do a google search on [ earth average surface temperature ], and pick an article to your liking.

I.e., is there any justification other than your own ideas for your running a trendline through peak global temperatures to show the correspondence of CO2 and temperature?

Yes, the clear limitations set by the Stefan-Boltman relation laid out in reply #90, the HITRAN analysis of IR absorption in CO2 watervapor system done by Hug, the joint paper with additional additional investigation done by Hug & Barret presented to the the DECHEMA colloquium, 2001,

Sooo... while Crowley and Berner show major variations in net forcing due to CO2 variability, your analysis does not.

Crowley and Berner show major variation in net forcing due to many factors of which CO2 is only one offered possibility. You are leaving out the other obvious and primary factors claimed for the initiation of deep iceages such as Plate Tectonics, Gamma Ray Bursts, meteoric and volcanic events, etc. All of which initiate atmospheric cooling incident to the creation of high altitude cloud cover & icefields altering the albedo of the earth.

I do not know how to reconcile this discrepancy.

Albedo effects from changing cloud cover & especially the creation of glacier ice, lower overall absorbed irradiation of the earths surface and hence cools the surface into ice age conditions. Under such conditions the major multi-million year iceages are induced.

Remove those effects from the overall record. What is left behind is a residual that can be perceived as the 1^oC change across a 500 million year record. A 1^oC change for more than 4 doublings of CO2 concetration consistant with:

the limits derived from the Stefan-Boltzman relation, in reply #90;
Pagani et al. (1999);
Pearson and Palmer (1999);
Pearson and Palmer (2000);
Cheddadi et al., 1998;
Raymo et al., 1998;

and many more.

Last point, regarding the temperature and CO2 variability over the past 420,000 years. It is indeed true that temperature increase preceded CO2 rise each time. This is fairly obvious, and likely primarily due to release of CO2 from a warmer ocean. The current situation, however, is without precedent, as the CO2 concentration has exceeded the boundary conditions for atmospheric CO2 concentrations over that interval by about 80 ppmv. This is why predictions of what will happen are difficult to compare to the paleoclimate record.

Not difficult at all, at least for estimating the effects of CO2 on climate. 0.277_oC per doubling of CO2 regurdless of the source of that CO2.

Now any other changes in global temperature can be due to many factors GHG's being only a portion of the issue, but CO2's contribution is so low in comparison with Water Vapor and the effects of Ice and Clouds on albedo, that CO2 can be essentially neglected as a substantive contributor to Earth's climate.

TABLE 4a.

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%

And now for the next installment of our discussion.

Based on what we've discussed so far, you've created an analysis of peak global temperatures in the Phanerozoic that purports to show a maximum 1 deg C influence from variable atmospheric CO2 concentration. This analysis is based on the Hug and Barrett spectroscopic results that indicate the maximum amount of heat/energy (?) that can be generated by the radiative forcing of atmospheric CO2. This is what I have gathered so far, and I will note that we have previously discussed this. I will return to Hug and Barrett further down.

In the course of this discussion, the first aspect of the discussion was addressing the paleoclimate temperature curve, where CO2 concentrations are superimposed; the CO2 concentrations are from Berner's modeling work, which is why I had the idea to bring him and his work into the discussion. It was fortuitous that the publication of Veizer et al.'s work prompted both the publication of Crowley and Berner's Science paper and commentary from Dr. Lee Kump.

The 'conventional' view of Crowley and Berner, and Kump, is that atmospheric CO2 concentrations are a driving factor in Phanerozoic climate. The radiative forcing due to CO2 is only modified by variable solar luminosity. Peak radiative forcing periods correspond with warm epochs, and minimum radiative forcing periods correspond to glacial epochs. The primary exception to this is the short Late Ordovician glaciation, which is explained as due to a unique continental arrangement where the Gondwanaland continent was very close to the South Pole.

Berner's modeling work incorporates plate tectonics and erosional weathering as a major aspect generating and controlling atmospheric CO2 concentrations over Phanerozoic time; therefore, plate tectonics are not an "alternative" explanation for the variation in radiative forcing, as you suggested. It strains credibility that gamma-ray bursts would influence climate over the multi-million year range covered by the Phanerozoic model to such an extent as determining Earth's major glacial epochs. Crowley and Berner due allow that the complexities of climate modeling may possibly provide an explanation of Veizer et al.'s results, which indicated that CO2 was not a strong influence on long-term climate patterns. This explanation is only deemed necessary IF Veizer et al.'s results are confirmed by "further scrutiny", which has not yet taken place.

Many researchers on climate and paleoclimate have called what humans are doing, i.e., increasing the CO2 concentration of the atmosphere due to fossil fuel burning and land-use changes, a "great global experiment", the results of which are difficult to predict. That is quite true; the fact that the CO2 concentration range shown in the Vostok ice core (which I have found according to one reference is accurate to +/- 5 ppmv) has now been exceeded by 80+ ppmv in a span of less than 200 years makes the outcome of such a perturbation difficult to determine, particularly if the radiative forcing due to CO2 and climate sensitivity are in alignment with conventional, rather than unconventional, climate research results.

New to this discussion is the published paper indicating that the Paleocene- Eocene Thermal Maximum, likely caused by a major methane hydrate release and subsequent CO2 production, was due to the radiative forcing of atmospheric methane and CO2. This event fulfills many of the requirements that would be desirable in a natural analogue to modern-day conditions, i.e., the natural release of greenhouse gases and an indication that the temperature response of the climate is in accord with theoretical prediction. An alternate theory based on unconventional science would have to provide a plausible explanation for the observed data (much as conventional science must provide a plausible explanation for the Late Ordovician glaciation occurring during a period of high atmospheric CO2 concentrations and high radiative forcing).

We can then bring up the subject of climate sensitivity. In essence, the position that CO2 has a minimum effect on climate is due to two factors: a posited low radiative forcing due to CO2, and a posited low climate sensitivity to variable radiative forcing factors. Below is a discussion, gleaned from other sources, that provides some indications of why the low radiative forcing indicated by Hug and Barrett may be erroneous. However, prior to that, a short explanation of the 'conventional' view of modern-day climate sensitivity.

As a note, this Web site has a large number of publications relevant to climate sensitivity studies:

Climate Sensitivity Research Lounge

The following text was excerpted from this Web page:
The Lessons of History

"When the temperature, CO2 and CH4 curves are carefully compared, it is found that temperature changes usually precede CO2 and CH4 changes by 500-1000 years on average. This indicates that climate change causes CO2 and CH4 changes. However, these greenhouse gas changes are a positive feedback that contributes to the large magnitude of the climate swings."

"Climatologists are still developing a quantitative understanding of the mechanisms by which the ocean and land release CO2 and CH4 as the Earth warms, but the paleoclimate data are already a goldmine of information. The most critical insight provided by the ice age climate swings is an empirical measure of climate sensitivity."

"The composition of the ice age atmosphere is known precisely from air bubbles trapped as the Antarctic and Greenland ice sheets and numerous mountain glaciers built up from annual snowfall. The geographical distributions of the ice sheets, vegetation cover, and coastlines during the ice age are well mapped. From these data, we know that the change in climate forcing between the ice age and today was about 6 1/2 W/m2 (Figure 3). This forcing maintains a global temperature difference of 5 °C, implying a climate sensitivity of 3/4 ± 1/4 °C per W/m2. Although climate models yield a similar climate sensitivity, the empirical result is more precise and reliable because it includes all the processes operating in the real world, even those we have not yet been smart enough to include in the models." (all emphases are my own additions, above and below)

I apologize for the overly dramatic nature of the art accompanying this figure, but it was the only representation of it that I could find on the Web. It reproduces a figure that I viewed in a previous online presentation.

The following text was excerpted from this Web page:
Global warming

"As summarized in Box 4, most of the energy imbalance has been heat going into the ocean. Sydney Levitus (Reference 4) has analyzed ocean temperature changes of the past 50 years, finding that the world ocean heat content increased about 10 watt-years, consistent with the time integral of the planetary energy imbalance. Levitus also found that the rate of ocean heat storage in recent years is consistent with our estimate that the energy balance of the Earth is now out by 0.5 to 1 W/m2. Note that the amount of heat required to melt enough ice to raise sea level 1 m is about 12 watt-years (averaged over the planet), energy that could be accumulated in 12 years if the planet is out of balance by 1 W/m2."

So that is the conventional view of current radiative forcing, paleoclimate radiative forcing, and climate sensitivity. Note also that a direct query to Dr. Hansen elicited that the major climate positive feedbacks are relative humidity increase (thus the primary radiative forcing contribution of water vapor is not ignored, as some would suggest), and ice sheet/glacier albedo effects. NASA research results that were prominent in the media last week indicated that the Arctic perennial sea ice cover is in a state of decline. This is a positive feedback factor for two reasons; one, the albedo of the large ice area is reduced, and two, the heat absorption capability of dark ocean (compared to reflective ice) is increased.

Below is some discussion of Hug and Barrett's research work, excerpted from a newsgroup thread on that topic. I am not qualified to judge the accuracy of the comments, but I feel that they are relevant as criticism to those who understand this area far better than I do.

"As Barrett, Braterman and Courtney have all correctly noted, the principal infrared absorption bands of carbon dioxide are optically thick under atmospheric conditions. How, then can an increase in atmospheric CO2 result in increased absorption of infrared energy by the atmosphere? This is an argument that goes back to the early years of the 20th century. While the global warming potential (GWP) of CO2 is indeed smaller than that of other greenhouse gases, such as methane, nitrous oxide, CFCs and CFC replacement compounds, it is nevertheless not zero. It was already recognized in the 1950s that hot bands, high rotational levels and most importantly wing absorption of pressure broadened lines all contribute to a net radiative forcing by incremental CO2. Furthermore, this effect is not uniform throughout the atmosphere---the variation of pressure, composition, temperature and radiative flux with altitude must be explicitly taken into account when evaluating the overall GWP. These effects are all included in the radiative transport codes incorporated into the General Circulation Models from which a net radiative forcing of ~4W/m2 is estimated for doubled CO2 content in the atmosphere (which is one possible scenario for the mid-21st century)"

"Returning to Barrett and the other comments, they all omit (although I believe that it is well known to Shine and Houghton) that although the forcing directly due to increases in the CO2 mixing ratio is less than linear, any additional forcing will increase the vapor pressure of water vapor, amplifying the net effect. I believe this is included in the 4W/m2 figure quoted above."

"Perhaps the simplest way of looking at this is that at 300 K there will be a steady state population of CO2 in the lowest excited mode of about 7% assuming local thermodynamic equilibrium. For a mixing ration of 300 ppm this corresponds to a density of vibrationally excited CO2 of 4 x 10^14 molecules/cc. Why won't they emit IR radiation?? Remember, that for local thermodynamic equilibrium, for every one of these that de-excites via collision (and it takes many collisions to loose vibrational energy in a gas where the density of states in the collision partners is small) another is excited by collision. The situation looks a lot like the Hinschelwood mechanism

CO2 + M -----> CO2* + M k1 rate

CO2* + M -----> CO2 + M k(-1)

CO2* -----> CO2 + hv kr = ln2/tau

where tau is the radiative half life. the ratio of k1/k(-1) = [CO2*]/[CO2] so the rate of radiation is kr k1/k(-1) [CO2] and you can calculate the ratio of [CO2*]/[CO2] from the Boltzmann equation.

The following is from a different newsgroup thread; in previous FR correspondence I provided the first part of this quote.

"Comment on "The roles of carbon dioxide and water vapour in warming and cooling the Earth's troposphere" "
John Houghton
Spectrochimica Acta v.51A, p.1391-1392 ( 1995 )

"Sir John very politely, and carefully points out the problems, and goes on to explain that as the concentration of CO2 in the atmosphere increases, so too does the average height (about 6km) from which CO2 emits radiation in space. Since atmospheric temperature in the lower atmosphere falls with altitude, if nothing changes other than the amount of CO2, the amount of radiation to space is reduced. For atmospheric CO2, this reduction is about 4Wm^-2. To restore the Earth's energy balance the temperature thoughout the lower atmosphere has to increase - hence the enhanced greenhouse effect."

"There is also a response from K.P.Shine, whose "constructive criticism of a previous version of this paper" is acknowledged in Barrett's paper. He notes that the previous paper had been submitted to another journal, and he "firmly recommended rejection of that paper and continue to profoundly disagree with the conclusions he reaches" in his review. He then goes on to repeat the points of Sir John, with another couple added for good measure. All in good, clear English that is too often missing from such journals. ( Spectrochim.Acta Part A 51 p.1393-4 (1995) )"

-------------------

That should be sufficient 'fodder' for additional discussion on many aspects of this topic. I look forward to it. Already this discussion and related information acquisition has provided me with knowledge of a remarkable era in paleohistory, the Paleocene-Eocene Thermal Maximum, about which I had been previously unaware.

Based on what we've discussed so far, you've created an analysis of peak global temperatures in the Phanerozoic that purports to show a maximum 1 deg C influence from variable atmospheric CO2 concentration.

True, at least across that data that depicts most nearly constant factors other than CO2 and is of the magnitude of direct radiative forcing. One should remove data representing ice ages which can be attributible to many factors such as continental drift, catastrophic Volcanic & metoric events (e.g. K-T extinction) and Gamma Ray Burst events as the earth moves through the galactic arms ...

This analysis is based on the Hug and Barrett spectroscopic results that indicate the maximum amount of heat/energy (?) that can be generated by the radiative forcing of atmospheric CO2.

No it is based on the the Stefan-Boltzmann relation:

E=sT⁴

equating direct radiative forcing E(w/m²) with temperature T(^oK) at blackbody radiative equilibrium through the Stefan-Boltzmann constant.

Ramanthan (JGR, vol. 84, pp. 4949-4958) states:

"the direct radiative effects of doubled CO2 can cause a maximum surface warming [at the equator] of about 0.2 K, and hence roughly 90% of the 2.0-2.5 K surface warming obtained by the GCM is caused by atmospheric feedback processes described above."

From my rough Stephan-Boltzmann estimate

(391.58/5.67*10^-8)^0.25-288^oK = 0.277^oK (C)increase in surface temperature for doubling of atmospheric CO2 concentration.

And from the Phanerozoic CO2 vs T chart above:

0.27^oC change in Earth's surface temperature for CO₂ doubling is depicted in the following graphic:

Please note the phrase "is depicted". and merely showing while confirming the first principles of the Stefan-Boltzmann relation as it regards 4.45 doublings of CO₂ concentration going backward 540 million years to 7000 ppmv CO₂.

The addition of the red lines merely illustrates the magnitude of Stefan-Boltzmann. And the statements of Ramanthan as to the direct radiative forcing of a doubling of CO₂ concentration.

Hug Barrett and others merely attempt to quantify the effects that a nitrogen and water vapor atmosphere have on CO₂ radiative absorption/emission so that the amount of forcing attributable to changes CO₂.concentration can be isolated and measured.

Equating change in radiative forcing expressed as watt/m² with temperature change is a separate issue altogether.

The amount of direct radiative forcing (w/m²) must have the same effect on temperature ^oK regardless of source of that radiative forcing and that relationship is expressed by Stefan-Boltzmann.

To the contrary, the direct radiative forcing of CO2 is very much limited by Stefan-Boltzmann as previously shown ~0.2-0.3oC per doubling and this alone would invalidates a reliance on changing CO2 concentrations as a major causative factor of ice ages whether inducing one or ending such.

Now we're talking about two different things. A major glacial epoch is not the same as a glacial period (when the contrasting period is an interglacial). It would be helpful if you could see the Crowley and Berner figure, but I can explain it pretty easily. The whole Pleistocene period of glacial-interglacial oscillations counts to Berner as a glacial epoch, a period in which continental ice sheets were present. His Phanerozoic climate model doesn't have the time resolution capability of distinguishing glacial advance and retreat and the causes of them. I.e., the concentration of CO2 in the atmosphere, in concert with the global tectonic setting (meaning the continental arrangement, the presence, location, and height of mountain ranges) is the main determinant of global climate over periods of millions of years.

Other factors, particularly astronomical factors (though I did read a VERY recent paper by oceanographer Carl Wunsch that addresses Milankovitch forcing factors; he indicates that their influence should be much less than as has been promoted and understood, but the statistics are way, way beyond me) will determine climate change and global temperature over periods that are considerably less than "millions of years". It's obvious from the graph that we've shared that atmospheric CO2 concentration responds to these other factors. Did you notice that Hansen said, as I have said many times, that in this case CO2 acts as a "a positive feedback that contributes to the large magnitude of the climate swings"? Note that this means CO2 and other GHG concentrations act to magnify change in both directions, meaning increasing or decreasing global temperature, because of their radiative forcing effects! To whit, when global temperatures decrease, CO2 and other GHG concentrations decrease, which amplifies (perhaps even accelerates) the climate trend.

Changes in aldebo from melting ice today can no more be placed at the doorstep of anthropogenic CO2 change than temperature across time due to other factors.

That's disputable but not provable. Many of the scientists who have observed the loss of perennial Arctic sea ice have taken pains to make sure that they don't say that the melting ice is a direct consequence of global warming, i.e., GHG-induced climate change or global temperature increase. At the same time, they attribute the melting ice to the observed general warming over the Arctic, which has occurred in the same timeframe (obviously) as the global temperature trend. What I was trying to point out was that the radiative forcing due to ice loss is the same positive forcing factor that is found in Hansen's figure. So no matter what the cause of the melting Arctic ice, the result is a positive radiative forcing term.

What must be determined is the initiator of such warming & cooling events, and changes in CO2 concentration simply does not qualify for lagging in time as well as lack as an IR active substance in comparison with even very small concentrations of water vapor, coupled with the effect of high altitude ice clouds from Solar, interplanetary, and inter galactic events modifying albedo.

Here you state a vital point of convergence in our discussion. Yes, CO2 does not qualify as the initiator of warming and cooling events in the recent (420,000 year, or Pleistocene glacial period) paleoclimate record. I totally agree. Let me reemphasize: I totally agree. But what I have been pushing very strongly in our discussion is the fact that CO2 is a radiative forcing component of Earth's climate system. Increasing atmospheric CO2 concentrations (and the concentrations of other GHGs) should lead to increasing global temperature. The remarkable case of the Paleocene-Eocene Thermal Maximum seems to demonstrate an event in which most other climate components were stable (~unchanging), so that the only change was a rather dramatic increase in CH4 and then CO2 atmospheric concentrations, leading to an apparent large increase in global temperature. (Note also that this event was about 150,000 years long, not 200, leaving the question of how rapidly the climate would respond to this increase wide open -- and that's a very significant question.)

And then the bottom line is: since the mid-1800s, atmospheric CO2 concentrations have increased about 80 ppmv, and they will not stop increasing for decades. There are very few other radiative forcing changes happening in the Earth's climate system right now, though if the Sun launches a few more giant solar flares at us during what is supposedly the down phase of the solar cycle, I might have to change that statement. In the absence of other factors, the rapid increase in atmospheric CO2 concentrations, and the radiative forcing that results from that process, will have an effect on Earth's climate system. Since there is still considerable uncertainty about the magnitude of some negative forcings (particularly clouds), the net result of the GHG forcing is still quite uncertain. Hansen has stated that controlling black soot emissions would do much more than Kyoto x 10, and that technological advance can significantly slow the growth rate of CO2 in the atmosphere. Taken together, that would result in much less forcing than a "no change in current trends" scenario. I think he's right; I've said that before.

That's a lot to say. If there is any justification in calling "global warming" a "global warming hoax", it lies with the media that promote worst-case dire scenarios as if they were as plausible as the midrange, average, mean predictions. Obviously they aren't, but the headlines are more strident. Factually, atmospheric CO2 concentration is increasing, as are the concentrations of other GHGs, though I believe methane has hit a plateau for unexplained reasons. Increasing atmospheric CO2 concentrations are a positive radiative forcing factor. Increased radiative forcing is expected to have a noticeable effect on global climate.

The last three statements are straightforward, factual, and no hoax. Saying otherwise is not contributing to the effort to understand how Earth's climate responds to forcing factors, be they radiative or something else.

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?

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. 0.262 wm^-2 (irradiance*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 0.20^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 quarter 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*0.3/4 = 0.325 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 0.4875wm^-2, the remainder radiated to space.

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_rms.

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 * 0.53 wm^-2 = 0.4^oC_peak

That leaves as much as 0.25^oC_peak arising from other factors for that period in comparison to the ±0.14^oC_rms. (i.e. ±0.20^oC_p-p) curve fit error.

We must attribute 60% of the 20th century change to changes in solar irradiation with a remaining 40% to all other driving changes:

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

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.

60% solar to 40% solar unrelate forcings seems to be a reasonable division when using the IPCC/GCM 10 to 1 forcing multiplier.

As to whether or not that 10 to 1 multiplication bucketing multiple complex processes (volcanic action, dust & smoke airosols, etc) gives us any understanding of where that remainder 40% of forcing comes from is another issue altogether.

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.