Thank you for asking me to present this paper. I think it is an important juncture, especially given the recent Nobel Prize. Buchanan won the Nobel Prize for the concept called public choice, which predicts among other things that organizations that are largely in the public venue will have some sort of resistance to types of change that might change their role. It is very hard, when one tries to produce a scientific consensus with an organization like the United Nations for this concept not to intrude.
I would like to spend a few minutes showing you how difficult consensus is to form, and how consensus changes. In 1990, the United Nations produced its first scientific assessment of climate change. I was asked by my friend, Tom Karl, to review it. I was asked anonymously to review it, because at that point the issue had already been so politicized that some people who were thought to give critical reviews were not invited to the process.
In 1990, I wrote that the models that were being used were probably producing too much warming, and it was likely that there was something that was mitigating the warming. The review hypothesized, because of the increases that were being observed in cloudiness, that it would possibly be some type of aerosol or something like that. The review was profoundly ignored, which is not surprising.
In fact, the UN wrote in 1990 in the summary document, when the latest models are run with impressive concentrations of greenhouse gasses,that their simulation of the present climate is generally realistic on large scale.
Anyway, the problem was well known, because the temperature increase was not nearly what was projected, even by the models of that time. It was reasonable to assume that sulfate aerosols or something like that might be the problem, because the Southern Hemisphere temperature increase was greater than the Northern Hemisphere's increase. It is a very interesting history, by the way, in that the Northern Hemisphere should warm up first and fastest. But much of the warming of the Northern Hemisphere took place prior to World War II, which was really when the greenhouse effect took off.
At any rate, by the time we got to 1992, we could change the climate models a little bit, so that in the report that was prepared specifically for the Rio climate treaty, we now had climate models that changed the carbon dioxide concentration gradually, as opposed to changing it at once.
These models then formed testable hypotheses, because you could run the models backwards and see what climate was being projected to occur as the carbon dioxide concentration increased.
The most commonly cited of these models in the 1992 report, and remember, the 1992 report was specifically designed to back up the Rio treaty, was the model that came out of Princeton University, known as the GFDL model. To give you an idea of some of the resistance on this, the GFDL model run backwards on it's own internal carbon dioxide concentration for the Northern Hemispheres shows a very large and growing disparity that began to develop about three decades ago. This is what is fueling some of the debate on this issue.
I should point out parenthetically, in 1992 I requested the output from this model from GFDL and was told, no, I couldn't have it. I thought that was very strange, so I asked my graduate student, who nobody knew was my graduate student, to request it, and they gave it to him, and then we ran this model.
Well, anyway, you can see the problem. It gets worse when one looks at the satellite data. The satellite data is thought to be highly accurate. The Southern Hemisphere satellite temperature history from when the satellite goes up in 1979 to now shows a significant difference which has always been there.
In the Northern Hemisphere, it gets much worse. There is cooling from Mount Pinatubo on the satellite data. There is no trend in the satellite data itself.
Well, at any rate, what strikes me as rather interesting in all this is, if we go back to 1992 and we read what the UN said on that report, it said the observed warming is broadly consistent with model projections. Does anybody believe that? Then it was stated that the satellite data really don't reflect the ground-based temperature because of stratospheric ozone depletion, which would affect the top level of satellite data.
When we compare the satellite temperature and the ground- based temperature you can see something quite interesting.The only place where they agree is where the temperature record is the best, in other words, in the north temperate zone, where we have the good temperature records from the United States, the former Soviet Union, and Europe. That is where the two records are very much in agreement. So we have pretty good reason to trust the satellite data.
The satellite data also matches up very well with temperatures from 5,000 to 30,000 feet, as measured by weather balloons. Therefore, if the satellite does not see warming, it is probably not there.
In fact, what happened by the time we got out to 1995, the consensus process changes much slower than some of the more outspoken scientists on this issue. In 1995, the UN report says now, when increases in greenhouse gasses only are taken into account, most models produce a greater warming than has been observed.
That is an admission that the people who were marginalized to the process in 1992 and 1990, who said it is producing too much warming, that was supposed to be the squalling of a small group of skeptics, well, it turns out that that now is the consensus.
Having said that, let's take a look at the satellite temperature history. It is rather instructive, it is certainly is not a global pattern. What it is, is a warming of the mid- latitudes, primarily in the Northern Hemisphere.
Now, if one is going to hypothesize that sulfate aerosol, which we have heard so much about, is the reason for the lack of warming, I caution you that the sulfate regions of the planet are the regions that are warming, not cooling.
In fact, if we take a look at the model that best tracks the past climate, according to the new UN report, that model was published by Mitchell et al. on August 10 in "Nature" magazine. I would like to spend a couple of minutes talking to you about what that model really said, because I don't think a lot of people know.
It says, number one, if you run the greenhouse effect only, you get a warming of 2.5 degrees for doubling CO2. Then Mitchell states in the paper that that model is too warm. He says it does not track the climate over the last quarter century, it is too warm.
The change is 33 percent, if you put the sulfates in the model. You do get a model that tracks the past climate, he says, of the last 40 to 50 years. The surface temperature record, which is in some debate, shows a warming of about four-tenths of a degree in the last 40 to 50 years, and the overall warming in the model for doubling CO2 plus sulfates is 1.7 degrees. That leaves you 1.7 minus .4 degrees, 1.3 degrees. That is the remaining warming for a doubling in the model that best tracks the climate of the past.
That is a dramatic change from previous forecasts. When one cites a number of two degrees, that is not the number that is driven by the model that best tracks the past.
There is a problem with this, though. In the model with the greenhouse gasses only, temperature change by the middle of the next century by Mitchell, et al., with the sulfates, SUL plus greenhouse gasses only, in the high latitudes of the Northern Hemisphere these two models are very similar.
All scientists know that the greenhouse- only models have produced way too much warming to date in the high latitudes of the Northern Hemisphere. The one that supports the Rio climate treaty more than any of the others, the Princeton model, has a warming of 2.5 degrees poleward of 60 degrees latitude between 1950 and now. The net warming observed between 60 degrees north and the pole is zero in the last 45 years. There isn't any. It looks like this model makes the same error.
So when I was asked to review the United Nations report, the new upcoming second assessment, I requested what we call the transient output from this region , because it does look like it is making that error. I was denied five times, five separate requests for that data.
Now, if anybody thinks that this is an effective peer review process, I challenge them to respond to a denial of data to a reviewer. The problem is that when we do that, we are behaving institutionally much like Buchanan predicts. There will be a resistance on the part of the organization to change what may affect the organization. That I think is seminal to this issue, because the review process is very important in any scientific debate.
I have about seven minutes left, six at best. I am going to finish up with a totally boring discussion of why it is not sulfates, anyway. Academic scientists are paid to explore, wherever your mind takes you, you must go.
One of the things that we need to do is to ask the question, is it really sulfates? One does not say sulfates killed the warming, or are responsible for it merely by making another climate model that reduces the radiation input to the Northern Hemisphere. That is guaranteed to fit the data better. It has to, because it is too warm. You saw how well the model worked when we didn't have sulfates in it, not very well at all. If you reduce the radiation coming downward in the Northern Hemisphere, it will fit better, but that won't say the sulfates caused the problem. No, you have to do what a doctor would do. You have to use a diagnostic approach and ask, does the model that fails fail because of sulfates? That is a totally reasonable thing to do.
This is a mathematical formulation that explicitly tests that. I don't want to bore you with it. It was in the "Journal of Technology" about a year ago. What you can do is, you can test the observed patterns of climate change versus what was modelled.
I want to tell you the good news about the most important pattern of climate change in the summer. I wish people who disagree would have read this paper, because it says that the climate models have correctly captured in the Northern Hemisphere the most important pattern of temperature change in the summer. They have done it. This is quite an important achievement. Unfortunately, it is the model without sulfates. As it changed the slopes are correct. This behavior however is not typical. This is the behavior of a winter pattern over time in a climate model. This is reality. There are different signs. This happens all the time.
We can compare patterns and see how well we have done. The patterns do the following. The climate might not change and the model might not change. That is good. That means that the climate was not predicted to change by the model, and it didn't change. There can be the type one or the type two errors, where the observed climate change didn't occur or the modelled climate change didn't occur. There is pattern number four, where the observed model changes are correct, and pattern number five, the horrible mistake, where opposite to what you predicted happens.
I am going to take you on a tour through an increasingly sulfate-laden atmosphere. Southern Hemisphere winter has no sulfates in it whatsoever, for all intents and purposes. The first category is where neither the model nor the climate changes. That is what is called being half right. If you were in Atlantic City, you would get your money back on that bet.
With the type one and type two errors, everywhere that the model says the climate will change, it didn't, and everywhere that the climate changed, the model said it didn't. So there is no correct forecast of any of the observed climate changes between pattern number four and a sulfate-free atmosphere.
Go to the North Polar region in the summer. This is remarkable, how much the climate has changed in this region. Only ten percent of the observed climate or the predicted climate has not changed since 1933 in a statistically significant fashion. Climate moves around a lot. But all the change that was predicted didn't occur, and none of the change that occurred was predicted. That was all type one and type two error. No sulfates up there.
Northern Hemisphere has the sulfates. The sulfate effect is supposed to be greatest in the summer. Here we see the best performance on a hemispheric basis in the model, in the hemisphere where the sulfates are when the sulfate effect is supposed to be greatest.
When we look explicitly in the sulfate regions in the summer, the model performs extremely well. This is the type of climate change that is correctly modeled, and this is the type of non-climate change that is correctly modeled. There is very little error in the sulfate region. Only one problem: this is the model that was predicting the dramatic warming that didn't occur. This is the model that bases the 1992 convention, in large part. This is the model without the sulfates.
So now you see the problem, don't you? Sulfates are not the disease. But you can get it to act like they are the problem with the forecast. It is much like if you went to a doctor with an infection, and the doctor gave you steroids, which will reduce the inflammation. The climate model had an inflammation. It was too warm. So we put something in it that drives down the inflammation. Then we find out later that we did not affect the cause of the inflammation.
It is not sulfates. I think it is the fact that the upper atmosphere cooled above 30,000 feet when the models predicted that would start at 50,000 feet. That is why the clouds increased. That is why the warming is muted. That is why it is primarily in the night, and that is why it is primarily in the winter. The 1.3 degree upward that you get from the Mitchell model happens to be the exact same number that you get if you assume that the warming of the 20th century had something to do with the greenhouse effect after all. If you went out to doubling CO2 at equilibrium, you would get a warming of 1.35 degrees.
Three more things. There are three separate sets of data that say the same thing. You can get this from the surface temperature record, from the satellite temperature record, from the weather balloon record, and you can get it from a critical analysis of the surface temperature. They all give you the same number. Nature is trying to tell us something here. Nature is running the model for you, and nature says that it is not sulfates, it is the greenhouse effect itself, not as large as was once feared, which is a nice thing to know.
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