The global warming crisis

Humanist, Nov-Dec, 2005 by Stuart Jordan

THE EVIDENCE IS OVERWHELMING that the Earth's surface is warmer today than it was a century ago. As for why this is so, research by thousands of scientists strongly suggests that the cause is the largely uncontrolled and still increasing release of anthropogenic (human-caused) greenhouse gases. Yet there remain a few scientists who oppose these conclusions, claiming that either the evidence for significant global warming is unreliable or that, granting the problem, the sources are natural cycles over which we have little or no control.

This isn't a mere academic debate. The conclusions held by leaders in a variety of fields can't help but have a profound impact on social, political, and economic policy. Thus each side has expended considerable effort to convince the public, and through it the political establishment, of the validity of its stance. But because neither has been entirely successful, particularly in the United States, policies have been inconsistent and changeable, subject to partisan wrangling, corporate lobbying, and a general inadequacy of resolve.

The importance of the issue was most forcefully brought to the public's attention with Hurricane Katrina and Hurricane Rita. Their unusual severity, being among the strongest ever recorded in the Gulf of Mexico, reminded a number of network newscasters of recent scientific reports predicting an increase in hurricane severity.

For example, the article "Extreme Weather: Is Global Warming to Blame?" in the May/June 2005 E/The Environmental Magazine quoted Ruth Curry, a Woods Hole Oceanographic Institute research specialist, saying, "Sea surface temperatures all over the tropics are running 1.8 to 3.6 degrees above normal. This is due to global warming." The article's author, Jennifer Vogel, noted the relevance of this: "While ocean and atmospheric circulation is the engine of a hurricane, heat is the fuel." Her summation makes it all plain: "The general scientific consensus on climate change and hurricanes is this: Hurricanes won't necessarily become more frequent, but they will become more intense."

This view was further supported by Massachusetts Institute of Technology climatologist Kerry Emanuel, writing in the July 2005 issue of Nature. He reported research suggesting that violent storms originating in the Atlantic and Pacific since 1970 have increased in intensity and duration by approximately 50 percent.

But on August 2 the National Oceanic and Atmospheric Administration raised its 2005 Atlantic Ocean hurricane forecast, predicting eighteen to twenty-one tropical storms: nine to eleven of which would become hurricanes and between rive and seven expected to reach major hurricane status. By October 9 the season had already yielded twenty tropical storms, eleven of which became hurricanes and rive that were major. By contrast, a typical Atlantic storm year has only six hurricanes with two to three being major. That this is part of a new trend over recent years emerges from the NOAA's statement that "these very high levels of activity are comparable to those seen during August-November 2003 and 2004" The conclusion would seem to be that, with global warming, hurricanes are becoming not only more severe but also more frequent. And the mainstream media is paying attention.

In such a scientifically--and politically-charged atmosphere, more people need to become familiar with the scientific evidence and understand the nature of the debate so they can respond knowledgeably and communicate with policymakers in an informed way. Toward that end, this article aims to assess that weight of evidence to see if it is, in fact, sufficiently alarming to recommend more than cosmetic action. It will also review the debate itself to see where the trouble lies and what the political dimensions of the problem have become.

WHAT IS THE EVIDENCE THAT SIGNIFICANT GLOBAL WARMING IS OCCURRING?

If the summarized results of thousands of scientific studies that appear in the Report of the Intergovernmental Panel on Climate Control-Climate Change 2001, The Scientific Study, hereafter referred to as the IPCC 2001 report, are valid, the answer is unambiguously that significant global warming is occurring. Yet there are still a few dissenters in the scientific community, albeit a small minority. As a result, it will be necessary to examine the evidence and the arguments on both sides.

Climate scientists define global warming as the measured increase in the mean Earth surface temperature over a specified time interval. The most reliable data are properly averaged over land and ocean surfaces, statistically weighted according to the density of measurements within each equal-area element. The final averaging is done for the entire surface of the globe.

So, according to the IPCC 2001 report, the Earth's surface has warmed by approximately 0.6 degrees Centigrade over the twentieth century. That is approximately one degree Fahrenheit. The warming hasn't been uniform over the globe, however. In general it has been greater over the land than the oceans and, probably for that reason, greater over the northern hemisphere than the southern. This isn't surprising given the greater thermal inertia of the oceans due to the high heat capacity of water. There is also some speculation that the greater industrial activity, hence greater greenhouse gas emission, in the northern hemisphere may have contributed. However, because the main greenhouse gases are well mixed--staying in the circulating atmosphere for a long time--this effect may be small or even negligible.