Brian Alworth on Climate Change

Brian Alworth Writes on Global Climate Change (Initial contribution: 4/7/01 Update added: August 22, 2003)

(Brian Alworth is a broadcast meteorologist and a member of the Trail of Tears Group living in Cape Girardeau.) 

The prospect of global climate change resulting from human activity presents serious social, economic and environmental challenges. And certainly the threat of “global warming” has generated serious public debate - recently put back on the front pages by the Bush administration’s decision to abandon the Kyoto agreement on greenhouse gases. 

But the basic “if, why, and how much” of global climate change is a scientific problem. And other than an occasional international study, generally broadcast through the distorting lens of the popular media, the atmospheric science community itself has been relatively quiet on this crucial subject, at least in public. Is this a sort of scientific negligence, or political timidity? Or could it be that the atmospheric science community is being asked to give simple, easy answers to extremely complex and uncertain questions?  

In 1990 the American Meteorological Society (AMS) adopted a policy statement expressing concern about human-induced climate change, but cautioning that there was a serious lack of confidence in the specifics. To quote directly: “The theory of how these greenhouse gases directly influence the earth’s energy balance is not controversial. If no other factors counter their influence, increases in their concentration will lead to global warming. However, the magnitude and timing of climate change are controversial because of uncertainties in our knowledge of all factors which may influence future climates and of the interactive processes which may act to modify the direct influence of the greenhouse gases.”

Since the AMS policy statement was published over a decade ago some things have changed, and yet enough has stayed the same that the AMS has not updated that 1990 paper. Certainly more evidence has accumulated that the earth’s climate is warming: thinning polar ice, receding glaciers, and some of the warmest years on record.

More scientists have become convinced that human activity may be responsible - and that the continued release of greenhouse gases is at least partly to blame. And yet questions about the future of global climate change have, if anything, continued to multiply.

The basic problem is that the earth’s climate is an incredibly complex system involving the atmosphere, land, oceans, lakes and ice-covered surfaces. In weather forecasting, for example, many complex feedback mechanisms can be ignored because of the relatively short time scales involved. By contrast, the accuracy of climate prediction is compromised by feedback mechanisms that operate on the same time scales as the forecast period. For example, some of the first simple climate models essentially just raised the carbon dioxide amount in the atmosphere and measured the resulting warming. In reality, of course, the situation is more complex. Increasing the level of greenhouse gases in the atmosphere eventually leads to changes in moisture, precipitation, oceans, and even vegetation patterns, all of which in turn will feed back to the atmosphere.

As examples of the ongoing discussion - in October of last year a research paper in the AMS Journal of Climate predicted that a warming atmosphere would mean thinner cloud cover and therefore less “cloud cooling” in a warmer climate. In fact the NASA scientist that authored the paper wrote that the amount of warming predicted previously by scientists should be increased by “at least 1 degree (F) as a result of the new findings..” Just a few months later, a paper in the AMS Bulletin by scientists from NASA and MIT found that a warming Pacific Ocean would likely lead to less cirrus cloud cover, creating a “heat vent” that could significantly decrease global warming. And recent research by atmospheric scientists at Colorado State University seems even to cast into doubt the supposition that greenhouse gases are the most critical issue. In a paper dated March 2001, Dr. Roger Pielke writes that “Human-caused land use change has an effect on local, regional, and global climate that is at least as important as currently expected to be caused by the radiative effect of the anthropogenic doubling of the effective greenhouse gas concentrations.” In other words, deforestation, desertification, urbanization, and vegetation changes due to increased carbon dioxide could have as much or even more effect on global climate than greenhouse gases. The conclusion: human-induced climate change is likely to be even more significant, and less predictable, than is widely believed.

So, yes, there is still scientific debate over global warming. But the debate now is less about whether it will occur, than how it will occur. Will it be faster or slower? Disastrous or moderate? And will the major player be greenhouse gases, or some other mechanism like land-use change? As the many influences on the earth’s climate system are better understood and global climate models improve, a clearer forecast will gradually develop. Popular media, and advocacy groups like the Sierra Club need to take care not to oversimplify the ongoing debate. At the same time, policy makers and politicians should not be allowed to use that debate as an excuse to mislead the public about the seriousness of the threats involved, or to avoid making unpopular decisions.

Update:     In the few years since I wrote this, the evidence for global warming has become stronger.  In particular the year 2002 was according to world weather data the second warmest year on record, just behind 1998.   Some of the most dramatic evidence of warming in recent years has been seen in the polar regions…which fits with what has been predicted by many global climate modeling studies.   Interestingly- despite June 2003 being unusually cool locally- it went into the record books as the second warmest June on record on a global basis.   Parts of Europe recorded their warmest June in hundreds of years. 

                  More and more, weather experts are coming to accept global warming as a fact rather than as a possibility.    Much of the discussion at present deals with what percentage of our ongoing warming is due to natural climate change and how much is due to human influence.   Greenhouse gas increases and continued deforestation can be measured..….but some natural cycles are possibly at work as well.  Within the weather community the feeling is that at least some percentage of the warming is indeed due to human causes.  Of course there is still much uncertainty as to how large that percentage is.   

                  As someone who works in a field where the public and science interact…it is interesting to note the lag between science and public perception.   Whereas public and political discussion continues as to whether ‘global warming’ is real or not….the atmospheric science community has moved beyond ‘if’ to discuss ‘how and why’.