Posted on 05/11/2004 7:56:43 AM PDT by cogitator
Observations Not Models
NASAs James Hansen widely is credited as the father of the global warming issue because of his 1988 congressional testimony concerning his detection of a human influence on world climate. His work with a General Circulation Model developed at the Goddard Institute for Space Studies led him to that conclusion, just as GCMs subsequently led others to the offer up scary scenarios of our climate future. It is remarkable, then, when Hansen writes in the March 2004 edition of Scientific American (PDF) that the climate change scenarios put forth in the Intergovernmental Panel on Climate Changes (IPCC) 2001 Third Assessment Report may be unduly pessimistic and that the IPCC extreme scenarios are implausible.
In Defusing the Global Warming Time Bomb Hansen argues that the observed trends in atmospheric carbon dioxide and methane concentrations for the past several years fall below all IPCC scenarios. As a consequence, he concludes, future temperature rise will most likely be about 0.75ºC over the next fifty years.
In reaching this conclusion, Hansen relies on simple empirical evidence he considers more precise and reliable than model results 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. As a consequence, he and the University of Virginias Patrick Michaels, a climatologist characterized by many as representing the opposite pole of scientific opinion on this issue, find themselves in agreement.
Michaels, like Hansen, believes the IPCC scenarios in large part overestimate the potential temperature rise in the coming century. And like Hansen, Michaels relies on observations for his insight into future climate behavior. In his 2002 Climate Research paper Revised 21st century temperature projections, Michaels writes, [Observations] are the perfect integrators of all processes that are currently active and thus avoid the varying degrees of uncertainties surrounding every aspect of the models.
Michaels used observations of the rate of the observed buildup of carbon dioxide in the atmosphere, along with observations of the global temperature change during the past twenty-five years or so, to determine, Our adjustments of the projected temperature trends for the 21st century all produce warming trends that cluster in the lower portion of the IPCC TAR range. Michaels concludes the warming during the next fifty years will be somewhere near 0.75ºC precisely the conclusion at which Hansen arrived two years later. Sadly, this is where most of the agreement between the two climate researchers ends. Note from the poster: this is double the rate of warming in the 20th century.
Hansen says it is imperative that we undertake concerted and organized efforts to lower this warming rate even further in order to avoid what he describes as dangerous human interference with the climate system (thereby echoing the words of the 1989 United Nations Framework Convention on Climate Change, a/k/a the Rio Treaty). He declares the emphasis should be on mitigating the changes rather than just adapting to them.
Michaels argues such a likely and modest temperature rise is one to which earth and its inhabitants can readily adapt. He contends it may even offer great advantages longer growing seasons, reduced heating costs, enhanced global vegetation, and so forth. Because the rate of climate change is manageable, Michaels believes, it isnt necessary to induce changes in the global energy structure. He advocates allowing market forces to dictate change because fossil fuels are finite and mankind will have to develop alternative energy sources.
How can two scientists who base their conclusion upon a collection of empirical evidence end up so at odds?
Hansen says his biggest concern is the potential for a large rise in sea-level. Yet empirical evidence shows that the rate of sea-level rise over the course of the 20th century (during which there was about 0.75ºC of warming) was about 1.8 mm per year. Therefore the cumulative rise over the past 100 years has been about 7 inches. Double that rate, as implied by a continued steady rise in temperature, and in most places there are no problems that cannot be controlled or adapted to. **see note below in comment
Other lines of evidence demonstrate the potential for positive impacts. Research by Ramakrishna Nemani and colleagues (who studied variations in global vegetation patterns based upon data collected from satellites) shows a remarkable enhancement of the growth of global vegetation. They attribute the growth to two decades of change in the climate and to the increased atmospheric concentration of carbon dioxide, which acts as a plant fertilizer.
The litany of dire consequences that could result from global warming generally is in step with the magnitude of the warming. In the IPCCs Third Assessment Report the range of potential warming manifest by 2100 is presented as being between 1.4ºC and 5.8ºC. The IPCC does not indicate which value is more likely. However claims of drastic future consequences are based upon the possibility of temperatures ending up on high end of the IPCC range (for instance see the claims made by the environmental organization The Bluewater Network which are reportedly behind some recent climate actions by Senators John McCain (R-AZ) and Ernest Hollings (D-SC), http://www.co2andclimate.org/wca/2004/wca_14c).
If one looks at actual evidence (rather than modeled responses), as do Hansen and Michaels, it is the lower end of the range that is more likely. The impacts associated with warming at the low end of the IPCC TAR range are far less dramatic and infinitely more manageable than those that accompany high-end warming.
It seems about time to dispense with the notion that future warming will be catastrophic and begin to focus on the implications of a modest warming where benefits are likely to outweigh costs.
(click on article link for references)
Good point. There is kind of an awakening to the utility of ethics these days. Scientists probably don't study much philosophy while they are getting their academic credentials and so don't become fully aware of their responsibilities until the real world intrudes. There has been some neglect there, and eventually neglect will demand payment.
"A majority believe that the longer trend will be downward."
- U of Wisconsin climatologist Reid Bryson, in his 1976 preface to Lowell Ponte's book :'The Cooling'
It sounds as if Micheals is being disengenuous, but this statement by Hansen is disingenuous as well. This period of most rapid melt also occurred when glacial ice was located as far south as the Washington DC region and is not applicable to the present day scenario where glacial ice is found only in Greenland and Antarctica. And rapid desalination of the North Atlantic from this melting of mid-latitude glaciers would have accelerated the warming/melting of glacial ice. Also not applicable to present day scenarios - but Hansen implies that the present day warming trend will similarily affect near-polar region glaciers.
That is known to be false. Sorry. He just takes past warming and past CO2 and gets one coefficient between them (a slope, in effect). And then current trends in CO2, which he projects forward. Then he imputes a change as large as the CO2 change to the temperature response.
But we know that the CO2 change cannot cause a temperature response that big. It does not produce enough power. Additional power effects equilibrium temperature as the 4th root of the power. Increasing CO2 gives slightly less than linear increases in power (near linear for small changes, but less for large ones as there is some saturation diminishing returns as the sky becomes opaque from below in CO2 frequencies).
The known physical relationship is more CO2 means slightly less than linearly more power, and more power gives a fourth root response in temperature. Instead he just uses linear. The handwaving that this is "simple and empirical" is still hand waving. For a small change you can project the current temperature trend - which is less than this, half. To predict a doubling in the current temperature trend based on the CO2 trend, when we know to a physical certainty the CO2 change cannot cause that big a temperature response, is just the correlation as causation fallacy.
They can't name the power source even for 0.75C in 50 years. 0.4C in 100 years is a more likely figure, from the power sources they can actually name. What we are seeing here is some pressure for realism entering, from the scientific as opposed to the activist side, as it becomes clearer and clearer they have no energy budget to support their scare quote predictions. Meanwhile we get Hollywood nonsense more extreme than the stuff being admitted here to be unfounded.
Hanson has come about half way to reality with this change in his projection. He still has half way more to go.
Understand what happened here. The headline predictions implied huge new power terms to sustain the higher temperature. Skeptics looked for where the models were supposedly going to get all the power from. And it just wasn't there.
They had power terms an order of magnitude too small for their predictions, from real verifible causes like direct CO2 greenhouse. They don't even pretend to know where the rest of it is supposed to come from. They waved their hands and said maybe feedbacks and maybe water vapor, and over time a half a dozen other candidates.
So people went and looked. And these extra power sources were always an order of magnitude too small and they had randomly distributed signs (plus or minus, forcing or damping) to boot.
And they then said the models have no cloths. The predictions are assertions they can't defend, as they have no power budget for them.
So what the leading adopter of those predictions originally has now done, is abandon model predictions and retreat to a linearly correlation and projection of current slope of one variable, atmospheric CO2, the one item for which they can actually show it does really give them power and enough of it to cause measurable warming.
But the power analysis already done has shown that the CO2 can only account for half of the trend he is now projecting, on this correlation alone basis. In a miraculous coincidence, the current directly measured temperature trend is half his correlation alone projection.
The known power terms and the known temperature trend agree. It is only a quarter of the UN's lowest projection and a tenth their mid range projection. Hanson is now projecting double the known power terms and known temperature trend. But to defend that twice as much, all he has is a linear correlation to a term (CO2) that we know, for physical reasons, can't cause a change that big.
It would be charitable to say the present real uncertainty, on the real science, is between Hanson and half of Hanson's figure, aka about the present trend. The present trend is a simple linear projection. It also just happens to agree with the expected response from the identifiable power. Hanson's is a simple linear correlation, to a projected accelerating variable, that can't name the other power source(s) that are supposed to provide the other half of the power.
And the UN and scare reports, the 3 to 5 C stuff? Just fantasy. Demolished by now, as science. But not abandoned by Hollywood, you can be sure.
Overall the process is working, but quite slowly, dragged kicking and screaming, because the hyper-political nature of the issue, and investments around it from outside of science, slow everything down and make everybody more than usually stubborn. But we will get there.
It will be interesting to see if Hanson now directs any of his fire at the continued IPCC-UN types, or instead insists that his own lower estimate is "still dangerous" yada yada. Whether he is trying to get the science right or to keep some defensible scare prediction, somehow.
You should read the linked Scientific American article before reiterating your points. You've always been very confident that you're correct; however, I think that your treatment is simplistic and doesn't take into account a myriad of climate feedback effects, the type of thing that predictive climate models use.
Read the article and then comment.
I'm afraid I don't see the relevance. The original poster inquired as to what factors initiated and terminated the glacial cycles that we refer to as "Ice Ages". My response was that the initiation and termination is primarily due to Milankovitch forcing. The Milankovitch cycles operate on several-thousand-year time-frames. I.e., the decrease in insolation leading to a glacial epoch due to Milankovitch forcing will take place over a period of several thousand years. There are feedbacks; as the insolation decreases, there can be a slow increase in the snow/ice cover. This increases the Earth's albedo, reflecting more sunlight back into space, leaving less to warm the Earth. Etc. These processes can "accumulate" slowly, to a tipping point where there is a fairly rapid (over a period of several hundred years) change in climate regimes, from warm to cold or vice versa.
So while your point was interesting, I'm not sure how it related to my point.
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