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Observations of anthropogenic global warming

Back in 1991: “Response to Skeptics of Global Warming”

Posted by Ari Jokimäki on October 21, 2010

About 20 years ago, William Kellogg wrote an article called “Response to Skeptics of Global Warming” which was published in Bulletin of the American Meteorological Society in April, 1991 (full text here). Let us see what were the issues then and what was Kellogg’s response.

Introduction

By 1991, the attention towards the anthropogenic global warming had increased considerably. Kellogg descibes how the greenhouse theory had been well accepted long time ago. The theory also had been tested by observations and observations also showed that the concentration of greenhouse gases were increasing in the atmosphere.

First controversial topic Kellogg mentions is this:

First, there is good justification for the view that there are just too many interacting factors involved in the extraordinarily complex system that determines our climate, and that we can never hope to understand all those interactions.

This is the familiar issue about the climate sensitivity and its uncertainties. The skeptic view that arises from this, as Kellogg describes it, is that no action should be made before the uncertainties about climate sensitivity have been reduced.

Second controversy:

A second motivation for resisting the temptation to take such action is the notion, being advanced in some quarters with considerable vehemence, that a global warming will be beneficial to the world as a whole, and we should do nothing to slow it down.

I quite like the phrase ‘resisting the temptation to take action’. :) Kellogg also notes the role of the media:

In the past year or two the media have reported the statements of a small cadre of scientists who disagree with the conclusions of the majority of those who are doing research on the climate system.

I’m resisting the temptation to ask after each quote here if they sound familiar. With these introductory themes Kellogg starts to address the skeptic arguments:

Let us take a critical look at what the skeptics, or “environmental naysayers”, are saying. We will not try to deal with every one of the points raised by them, but the following will discuss the more interesting and widely quoted ones.

So it seems that Kellogg pioneered the field John Cook is now mastering. The part about the “naysayers” has to do with Kellogg having just quoted a comment by Senator Tim Wirth.

The arguments and the response

Kellogg first addresses the argument about the uncertainty in climate sensitivity:

Yet the five or so most advanced climate models, developed over a period of many years by top notch teams, have all come to essentially the same conclusion: The global average surface temperature would probably rise by about 2 to 5 K if the greenhouse gas concentration were maintained at double the pre-Industrial Revolution level, which for carbon dioxide was 270 to 280 parts per million (ppmv).

However, Kellogg also points out that the models have problems in their resolution and other problems, but also that modelers recognize those issues.

The question of the recent surface temperatures in 1991 was stated as: “Why have we not already seen the greenhouse warming”? Kellogg says that the answer to the question is not clear but that there has been a warming trend in the past 100 years but that there are natural variability and other factors that can contribute to the warming. Kellogg then points out that the warming from greenhouse gases is a global phenomenon and should therefore show up in global temperature – and it does (and did in 1991). By that time, the global temperature record had just been complemented with sea surface temperatures, so there were newly acquired confidence to the record. Let us take another “sound familiar?” quote:

[Global average temperature] rose quite fast from 1900 to 1940, then more or less leveled off until 1970, and since then the decade of the 1980s has witnessed five record breaking years…

Then about the skeptic view:

…some still express doubts that there has already been a long-term warming due to the greenhouse effect (Barnett and Schlesinger 1987; Seitz et al. 1990; Lindzen 1990; Ellsaesser 1990; Reifsnyder 1989). It is not significant, they sometimes say.

Kellogg then performs a statistical test on the global average temperature during the 20th century and concludes that the signal has a over 98 % probability to be real. But he also points out that due to natural variability and other factors the attribution of the warming to the greenhouse effect is problematic. He concludes on this issue:

So some of the more cautious policy makers who are listening to our debate can, at least for the time being, cite the IPCC report and argue that they have another ten years or so to wait before remedial action will be justified by “unequivocal” evidence.

The next issue is the United States temperature record. In 1991, the situation was that there were some papers showing that lower 48 states of United States had not warmed in last hundred years. Kellogg describes the media take on the issue:

The press has published this finding as evidence against the conclusion that the world had become warmer. What they often fail to add was that the U.S. (lower 48) occupies less than 5% of the area of the globe, so what happens in the U.S. can hardly be considered to apply to the world as a whole.

Kellogg the points out that it is actually only the eastern part of the United States that had experienced cooling. He also adds that the effect of urban heat island complicates things further so that there actually should be even more cooling showing in the United States temperature record. To this he says:

However, even if this bias exists at urban climate observing stations on land in other parts of the world, it can hardly have an influence on the COADS marine temperature record. Thus, the combined global surface temperature record, shown in Fig. 1, must be accurate enough to demonstrate a real warming trend, and the urban heat island effect on the land stations is considered to have less than a 0.05 K effect on the average (Folland et al. 1990).

Kellogg then addresses a claim by Lindzen that global warming has not begun because North Atlantic has been cooling slightly during about 50 years before 1991. Kellogg says this is just another regional result and that land areas have warmed faster which is no surprise because in ocean temperature there are other factors than radiation balance slowing the ocean warming. Kellogg the explains some model results relevant to the explanation of this ocean cooling.

Next claim to be addressed is the claim that satellite records show that there’s no warming. There had been a NASA report describing 10 years of satellite data which showed no clear trends. There had been some claims that this means there’s no global warming. Kellogg explains why this is not so:

The point is simply that one cannot demonstrate a 100-year trend by looking at a 10-year segment of the record, particularly when there is so much natural fluctuation in the record.

That is not all, there’s another problem with satellite records:

The oxygen emission measured by the satellite instrument actually comes from a region of the atmosphere extending from near the ground up to the tropopause, and it may sometimes include part of the lower stratosphere. … Thus, the temperature of a very deep portion of the atmosphere is being sampled, and the upper part of this layer is expected theoretically to show a cooling trend rather than warming. This fact suggests that such microwave observations may not be suitable for monitoring the year-to-year progression of the greenhouse effect, during which the warming should occur mainly in the lower part of the troposphere.

To the claim that the observed warming trend is due to sun, Kellogg says that while you can explain some of the fluctuations in climate records by solar and volcanic activity the explanation of longer term trends with them is problematic:

However, no long-term trend is evidenced unless the progressively important greenhouse effect is also introduced as a third-forcing function (Hansen et al. 1981; Gilliland 1982).

Kellogg then discusses some detailed issues regarding the solar forcing.

Next issue is the negative feedbacks in the climate system. Apparently, there had been some claims that there might be some strong negative feedbacks which are not included in the climate models. That would then lower the climate sensitivity. Lindzen’s iris hypothesis is mentioned specifically. Kellogg makes some objections to the hypothesis including some observations showing that water vapor in the troposphere has increased which is against Lindzen’s hypothesis. Kellogg concludes:

It thus appears that the critics of currently accepted assessments of climate change are going to have to continue their search for some powerful and credible (but hitherto overlooked) negative feedback mechanism that will greatly reduce the apparent sensitivity of the earth’s climate system to an increase of the greenhouse gases.

The cloudiness problem is discussed next. The clouds are a strong factor in climate and their modelling is difficult because of several factors including the coarse resolution of the models. Kellogg points out some observations:

Over the past 30 years the tropics have gotten warmer, especially over the oceans (Flohn and Kapala 1989), and in this period high clouds in the tropics (Ci and Cb) have increased, while lower and middle clouds (Cu and St) have decreased (London et al. 1991). Both of these trends in cloudiness contribute to a positive feedback, or warming.

Kellogg then describes some model results on cloudiness. There is a big spread in their results, so it seems that models need to be improved relating to the clouds, but observational evidence seems to be pointing to positive rather than negative feedback.

Then Kellogg moves on to the claim that climate change will be beneficial. This was of course rather controversial subject back then (and still is to some extent) so Kellogg points out that the majority of climate scientists see the climate change effects to be non-beneficial on the whole.

Looking back on Kellogg’s article now makes me think that it could very well have been written this year on some of its parts. Science has moved ahead on many issues discussed. Many of them were non-issues already in 1991, as Kellogg shows. Yet you see all of the claims discussed here presented even today, unchanged.

References

Kellogg, William W., 1991: Response to Skeptics of Global Warming. Bull. Amer. Meteor. Soc., 72, 499–511. [abstract, full text]

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One Response to “Back in 1991: “Response to Skeptics of Global Warming””

  1. Neven said

    Thanks, Ari!

    It’s amazing how people think that the climate change debate has just started. I realized how long things have been going on when I read Spencer Weart’s The Discovery of Global Warming.

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