CLIMATE CHANGE

May 2004
		A team of international ecologists using a computer model to predict the effects of climate change say as many as 1 million species could be on the way to extinction by the year 2050. One of the study's authors, Lee Hannah, and environmental experts Daniel Botkin and Patrick Michaels answer your questions.

Forum Introduction Will climate change act as a catalyst for new species? Is climate change the result of human activity or a natural phenomena beyond our control? Do we know anything about species extinction rates from the relatively recent "little ice age"? Can climate change be reversed, as opposed to deterred? Does the impact being made by humans in this (brief) period really explain world-wide shifts in climate? For every study that claims to observe climate change, there are others that seem to refute it. Wouldn't we all be better served by a global campaign to address air quality? What, if any, are the potential upsides of global warming?	David Burke of Merced, Calif., asks: In view of major weather fluctuations (notably ice ages) in the planet's history, does the impact being made by humans in this (brief) period really explain world-wide shifts in climate and allow for predictions in the short term (100 years or less)? Lee Hannah responds: Climate over the last 11,000 years has been among the most stable in planet's history and much more stable and warm than the previous 2 million years for which we have reasonably good temperature indications of past temperatures. Human-induced climate change will be huge relative to most of the fluctuations in that 11,000-year period. Patrick Michaels responds: Yes, because we are changing the boundary conditions for the climate by altering absorption of infrared radiation. That can be modeled (albeit badly at this time). It's a different change than induced the ice ages--which were largely related (at least for the last two of four) to Earth-orbital parameters and the building of mountain ranges in very critical places. At least that's the current myth, as they say ... the fact is that the changes in incoming radiation from the orbital variations are very small, and (in my mind) too small to induce an ice age unless pushed along by some peculiarities of continental drift, resulting in the rapid rise of the Himalayas and the chain of high mountains in all of the western boundary of the western hemisphere. These interact with the jet stream in a way that may make the Earth prone to glaciation. Having said that, one of the reasons I feel the current warming is "different" is its distribution. I published a paper in 2000 showing how it is inordinately confined to cold, dry air (mainly in Siberia and northwestern North America) and that this is highly consistent with greenhouse theory, which predicts that dry air must warm much more than wet air. In fact, the more dry air there is, the more it warms. As they say, Q.E.D.