Introductiom

The Bio fuels Conundrum debates about climate change have centered on a significant dimension: the steady increase, notably over the past too years, in the average temperature of the globe. Global warming has thus come to dominate the policy discussions that now surround the relationship between climate and energy. This issue has both a future and a past. The planet is already warmer on average by about 0.7°C. But much of the debate about future climate policy focuses on the challenge of predicting what will happen in the next Zs, so, or too years. That will be the subject of the next section of this book, but it is important to note here that much of the discussion about whether "global warming is real" concerns scientific disagreements about the general circulation models (Gums) that are used in making predictions and their capacity for producing accurate forecasts. The authors of this book believe that the weight of the evidence favors the conclusions summarized in the most recent reports of the Intergovernmental Panel on Climate Change (IPECAC). These project, first of all, that by mid-century, average global temperatures will have increased by between 2.5°C and 7.0°C, and sea level will have risen between about 20 and 70 cm. A combination of model prediction and the continuation of human activity in releasing carbon dioxide into the atmospherethrough the combustion of fossil fuels or the burning of forests—leads to those conclusions. There is some scientific disagreement here. It is believed by many scientists that the IPECAC consensus underestimates the extent of sea level rise. An important issue here is whether the warming of Earth's climate will continue in a steady, ramp-like increase in average temperature, or whether the temperature change might pass the threshold of a dynamic, nonlinear process that could alter the climate dramatically. Were the major ice sheets in the Antarctic and Greenland to experience sudden increases in the rate of melting, that could lead to much larger increases in sea level, which could change the dynamics of ocean circulation especially in the North Atlantic and produce much colder temperatures in Europe. The changes we have already observed, however, provide fewer sources for argument. Current models support that global warming will result in an increase of extreme weather events.