It wasn't long after I became a research scientist that I learned that scientists aren't the unbiased, impartial seekers of truth I always thought they were. Scientists have their own agendas, philosophies, pre-conceived notions, and pet theories. These views end up influencing their science. Nowhere does this have a greater impact on the science than in global warming theory.
When confronted with a new, policy-relevant science problem, there are always scientists that will immediately rush to judgment about a "possible" environmental catastrophe. In the 1970's it was an impending ice age. In the late 1980's it was inflated global warming predictions. Most recently both extremes have morphed into the possibility that global warming will actually cause an ice age for Europe. In an age when popular culture helps to blur the line between science fiction and reality, our imaginations are fired by the thought of an ice sheet advancing on a city, or unexplained increases in severe weather.
On February 4 I testified in a congressional hearing that was held to explore the role that science plays in public policy formulation. I tried to explain that science always involves assumptions, and so scientific conclusions are only valid if the assumptions hold up. And there are always additional, unstated assumptions that the scientist isn't even aware of!
For a complex problem like climate change, assumptions abound. Early in the climate modeling days, confidence was high as physicists used to working on well-defined problems with a limited number of variables thought they had the answer. We meteorologists (by training) were always more skeptical because we understood how complex weather is. Enter the scientist "heavy hitters" that are savvy public speakers, maybe a Nobel laureate in some unrelated field of science, all having strong opinions about what the government should be doing to help "save the Earth" and you have a recipe for bad policy. Now, the climate modelers are learning how complex the climate system really is (surprise!). The tendency for scientists to rush to judgment isn't the fault of science -- it's just human nature.
Even though I love details, I also am constantly striving to understand the "big picture." We have pretty high confidence that increasing carbon dioxide concentrations have a warming tendency. The Earth's natural greenhouse effect, mostly due to water vapor, keeps the Earth's surface and lower atmosphere warmer that it would otherwise be, and the extra carbon dioxide adds to this effect. But about 75% of that surface warming is never realized. All that water vapor represents huge amounts of heat that have been removed from the surface of the Earth, in a very real sense "air-conditioning" it, keeping the surface over 100 deg. F cooler than if weather systems did not exist. All weather systems act to redistribute heat, carrying it from where there is more to where there is less...the energy contrast is what drives them. So, the real question is, how will weather systems adjust to the warming tendency? Will they change their cloudiness or precipitation processes in such a way to amplify (positive feedback) the warming or suppress it (negative feedback)?
Our knowledge in this area of precipitation and cloud microphysics (which control the equilibrium amount of water vapor in the atmosphere) is so meager, that I would argue that it is a matter of faith to believe that the Earth will respond by amplifying the warming tendency. If the response is simply benign, then about 2 deg. F warming is about all we'll have to contend with in the next 100 years or so. But in the meantime, I wish all those global warming extremists would simply confess their faith -- and stop giving science a bad name.
Roy Spencer is a principal research scientist for University of Alabama in Huntsville. In the past, he was served as Senior Scientist for Climate Studies at NASA's Marshall Space Flight Center in Huntsville, Alabama. Dr. Spencer is the recipient of NASA's Medal for Exceptional Scientific Achievement and the American Meteorological Society's Special Award for his satellite-based temperature monitoring work. He is the author of numerous scientific articles that have appeared in Science, Nature, Journal of Climate, Monthly Weather Review, Journal of Atmospheric and Oceanic Technology, Journal of Climate and Applied Meteorology, Remote Sensing Reviews, Advances in Space Research, and Climatic Change.