John Christy is associate professor of atmospheric science at the University of Alabama in Huntsville. In collaboration with Dr. Roy Spencer of the NASA Marshall Space Flight Center, the two have been using Microwave Sounding Units (MSUs) aboard NOAA's TIROS-N weather satellites to record temperature trends in the lower troposphere since 1978. Christy contends that satellites measurements of global mean temperatures in the lower troposphere show no warming trend over the past 20 years.
James E. Hansen is a head researcher at NASA's Goddard Institute for Space Studies. Hansen sparked the global warming controversy with his testimony to Congress in the summer of 1988 when he stated that the unusually high summer temperatures throughout North America were almost surely the result of increases in anthropogenic greenhouse gases. That same year, he used climate prediction models to show that a doubling of the concentration of CO2 in the atmosphere would lead to a significant rise in global temperatures with an associated negative social and economic impact. More recently, however, Hansen has expressed doubt concerning the accuracy of GCMs, stating that they do not adequately account for a number of complicated positive and negative feedback mechanisms which could serve to either increase or offset greenhouse warming.
Thomas R. Karl is a fellow of the American Meteorology Society and chairman of the National Academy of Sciences Research Committee. Currently Director of the National Oceanic and Atmospheric Administration's National Climatic Data Center in Asheville, N.C., Karl is a strong proponent of the enhanced greenhouse effect. He maintains that the temperature record indicates a warming trend due to greenhouse gas emissions that is "statistically higher than predicted by random chance alone", suggesting that mankind is the most likely cause for rising global temperatures (McDonald 1999).
Richard S. Lindzen is the Alfred P. Sloan Professor of Meteorology at MIT. A strong opponent of the global warming/climate change phenomena, he is one of many scientists who are skeptical due to discrepancies and inaccuracies in computer models used to predict future climate scenarios. In addition, he maintains that water vapor has been dealt with incorrectly by most global warming advocates, claiming that increased H2O vapor will have a negative feedback on global climate warming due to increased convection.
Patrick Michaels is Research Professor of Environmental Sciences at the University of Virginia and Virginia State Climatologist. Ecological and mesoscale climatology. Here is his "robust earth" quote from his website at UVA:
The core issue over the next ten years will not be "How much will the climate warm?" but, rather, "Why did it warm so little?" My research also leads me to believe that the next decade will see the emergence of a paradigm of "robust earth," as opposed to the fashionable "fragility" concept. The papers listed below provide some evidence for these observations. It is entirely possible that human influence on the atmosphere is not necessarily deleterious and that it is simply another component of the dynamic planet. Tomorrow's scientific and science-policy leaders will have to recognize this verity in our attempts to maintain a productive and diverse planet.
Stephen Schneider of Stanford University (formerly at the National Center for Atmospheric Research) maintains that immediate action must be taken to regulate greenhouse emissions despite the uncertainty that still exists. He supports investing in more efficient energy sources as "insurance" against the potentially severe impact that continued fossil fuel use will have on global climate.
S. Fred Singer is currently an environmental scientist and a professor at the Institute for Humane Studies at George Mason University, as well as Director of the Science and Environment Policy Project . Singer, a major opponent of global warming and climate change, maintains that the predictions of climate models are inaccurate due to the "heat island effect"; the phenomenon in which recorded surface temperatures indicate a false increasing trend due to rising population and urbanization. He holds that any greenhouse gas emission regulation will have a negative economic impact, particularly in poor and underdeveloped nations, and adds that politics is interfering with science in order to impose a political agenda.
Roy W. Spencer is Senior Scientist for Climate Studies NASA/Marshall Space Flight Center. In collaboration with John Christy, Spencer and Christy have been observing temperature trends of the lower troposphere as recorded by weather satellites since 1978. Together they have found there to be no evidence of global warming over recent years.
Kevin Trenberth is a climate scientist at the National Center for Atmospheric Research. In collaboration with fellow scientist James Hurrell, Trenberth found that sea surface temperatures covering the same period as satellites throughout the numerous locations in the tropics display a 0.12 deg/C temperature increase. This is in marked contrast to the data gathered by satellites, which display a cooling trend of approximately 0.01 deg/C. Trenberth and Hurrell's article in the March 13, 1997 edition of Nature fueled the debate over the accuracy of data gathered via satellite in relation to sea-surface temperatures records.
Frank J. Wentz is a remote sensing expert at Remote Sensing Systems in California. His essay published in the issue of Nature fueled the debate over the reliability of satellite data. Wentz pointed out that over time, there occurs a gradual lowering of the altitude of the satellites thus resulting in a false cooling trend. The process by which the satellites change the position of their orbit has been termed "orbital decay" and could be responsible for the observed cooling trend up to a magnitude of 0.7 deg/C.
Timothy E. Wirth is Under Secretary of State for Global Affairs and Counselor of the Department of State. Wirth's bill (S. 2667), proposed in 1989 called for a 20 percent reduction in carbon dioxide emissions by the year 2000. It also directed the Energy and Interior Departments to develop a revised national energy policy including energy conservation and renewal, as well as alternative energy sources. A proponent of global warming, Wirth has been committed to establishing tangible emissions targets for the United States.