2008-06-09_PERMIT FILE - C1980007 (6)

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Chapter 5 Table 5-1 DEIS Comments and Responses Commenter Comment Comment/Response after comment has most recently released Climate Change 2007: The Physical Science Basis period, no appeal Sununary for Policymakers, which summarizes many of the major findings.4 standing) Some of the science and policy implications are discussed briefly below. Scientists have demonstrated that anthropogenic greenhouse gas emissions have altered the energy balance of the earth by 0.85 + 0.15 watts per square meter (Hansen et al. 2005); due to the lag time in the climate system, this energy imbalance commits the earth to additional warming of .6°C (1° F) of warming that is already "in the pipeline," even absent additional greenhouse gas emissions.5 Leading scientists are now able to tell us, with a high degree of certainty, that additional warming of more than 2.0- 3.00 C (3.8-2.7° F) above year 2000 levels will constitute "dangerous climate change," with particular reference to sea level rise and species extinction. The "tripwire" between keeping warming above 2000 levels to less than 1.0°C (1.8° F) and between experiencing warming of more than 2.0- 3.000 (3.8-5.4° F) above 2000 levels depends on a very small amount of anthropogenic greenhouse gas emissions because warming of more than 1.000 (1.80 F) above 20001evels will likely result in climate feedbacks that will result in 2.0 to 3.0°C additional warming even without substantial additional greenhouse gas emissions. Furthermore, scientists are able to describe the likely atmospheric greenhouse gas level "ceiling" that must not be exceeded in order to prevent additional warming of more than 1°C (1.8° F) above year 20001evels; they tell us the ceiling is approximately 450-475 ppm of carbon dioxide, depending upon levels of other greenhouse gases, such as methane and nitrous oxide.b In order to stay within the ceiling, emissions must follow what has become known as the "alternative," rather than the "business as usual," greenhouse gas emissions scenario. In the business as usual scenario, carbon dioxide emissions continue to grow at about 2% per year, and other greenhouse gases such as methane and nitrous oxide also continue to increase. In the alternative scenario, by contrast, carbon dioxide emissions decline moderately between now and 2050, and much more steeply after 2050, so that atmospheric carbon dioxide never exceeds 475 parts per million. The alternative scenario should limit global warming to less than an additional 1 ° C in this century. Unfortunately, society so far has not followed the alternative scenario. Instead, carbon dioxide emissions have continued to increase by 2% per year since 2000. If this growth continues for just ten more years, the 35 % increase in emissions between 2000 and 2015 will make it unlikely we can achieve the alternative scenario.8 Just ten more years on cuiYent greenhouse gas emissions trajectories will essentially commit us to climate disaster. Dr. James E. Hansen, Director of the NASA Goddard Institute for Space Studies, and NASA's top climate scientist, has stated: "In my opinion there is no significant doubt (probability > 99%) that... additional global warming of 2° C would push the earth beyond the tipping point and cause dramatic climate impacts including eventual sea level rise of at least several meters, extermination of a substantial fraction of the animal and lant s ecies on the Janet, and major regional • • • 188 Deer Creek Ventilation Shaft and E Seam Methane Drainage Wells FEIS