Global warming is not just about temperature

As societal activities, especially fossil fuel burning and deforestation, add more...

  As societal activities, especially fossil fuel burning and deforestation, add more carbon dioxide and other greenhouse gases to the atmosphere, a definite but geologically small rise in the global average temperature can be expected. From my perspective as an Earth scientist, the dangers from global warming are all indirect consequences of the increase in temperature. Many of these, and more, were discussed by Richard Rehberg in a previous Press & Sun-Bulletin article. They include (but are not limited to):* an increasing frequency and intensity of hurricanes, as the oceans warm and air becomes more humid;* an increasing severity, frequency, and duration of El Niño events as the oceans warm;* an increase in extreme weather, including tornados and flooding, as well as cold spells and heat waves, and also the increase in dramatic day-to-day changes in weather, as the atmosphere becomes more energetic; and* significant changes in regional climate (with a possibility for, e.g., greater drought) as wind and ocean current patterns shift.These effects of these on plant and animal life will be more substantial than that of warmer air temperatures alone. Finally, add to these the effects of everything on society -- for example, consider the eventual migration of entire populations away from coastal zones as sea level rises, or the shift in world economic balance as crop belts move northward or southward -- and the concern about global warming is understandable.The potential danger of sea level rise is best appreciated within a geological context. Current rates of warming suggest an increase in sea level of roughly a meter by the end of this century -- a nuisance, certainly, but not sufficient to cause mass migrations. But there are some indications that the western portion of the Antarctic ice sheet is somewhat unstable, and has collapsed at times in the past.For example, the previous "interglacial" period, a time prior to the most recent growth of northern hemisphere ice sheets that began about 120,000 years ago, was a couple of degrees centigrade warmer, world-wide, than our current climate. But sea-level at that time was about 7 meters (23 feet) higher than at present, and geologists attribute that to a complete melting of the West Antarctic ice sheet. Thus, as we look to our future, it is possible that the West Antarctic ice sheet will rapidly melt away when global warming reaches a "critical" value, perhaps only a few degrees Centigrade higher than now. Because of differences in the causes of climate change during ice ages versus global warming, however, that critical value is difficult to determine.The various indirect consequences of global warming listed above are occurring now. The years 2003 and 2005 provide dramatic examples. You probably recall the European heat wave of 2003, causing the death of an estimated 27,000 people; how about the record number of tornadoes in the US that year, with 562 in May, or the region of South Dakota - which normally gets about 30 tornadoes per year - that was hit by 50 on one day in June? The 2005 hurricane season was marked not only by Katrina, but by Hurricane Wilma six weeks later; it grew from a tropical depression to a category 5 hurricane in less than 24 hours, and became the strongest Atlantic storm ever recorded.Indirect effects of global warming have struck upstate New York as well. For example, in Greater Binghamton, tornado activity has increased from almost nothing in the 1970s and 1980s to the point where tornado warnings became an almost annual occurrence during the 1990s, and occasional tornadoes have struck Vestal, Endicott, and the Town of Binghamton over the past 10 years. And remember the winter of 2003-2004, with huge snowfalls in Fulton (150 feet in one month) and Oswego (205 feet total) presumably fed at least partially by moisture from warmer and exposed Great Lakes?The world facing such consequences of a globally warmed surface will also be facing another (geological) complication: at some point in our future we can expect the demand for oil to irreversibly exceed worldwide production, as that non-renewable resource is finally and irrevocably depleted. Though the timing of this so-called "peak oil" crisis is disputed -- with some believing it is decades or more away, and others claiming it has already occurred (did you ever wonder why oil-rich countries in the Mideast are building nuclear power plants?) -- the point is that peak oil will represent a tough economic context within which to deal with all the consequences of global warming.If global warming is merely one further example of nature's variability, there is little hope that human action can stem its advance. Part Three of this article will explore the reasons for viewing it as a product of human activities, and considers the international accords that may mitigate its impact.