Transcript Lecture
Greenhouse gases, Climatic modeling, what can be done? Not Just CO2, Many Others!! CH4 (methane) N2O (Nitrous oxide – AKA Dinitrogen monoxide) H2O (Water vapor) O3 CCl3F (Freon 11) CCl2F2 (Freon 12) Greenhouse factors for these common gases Substance Greenhouse factor Tropospheric Abundance (%) CO2 CH4 N2O O3 CCl3F CCl2F2 H2O 1 30 160 2000 21,000 25,000 0.1 3.6 X 10-2 1.7 X 10-3 3 X 10-4 4 X 10-6 2.8 X 10 -8 4.8 X 10-8 1 Climate change Very difficult to predict future Many complex, interdependent factors Poorly understood relationships Predict local weather accurately? Predict massive climatic change? Worst case scenario Worst Case Predictions: CO2 in atmosphere increase to ~550 ppm by 2050 Temperature increases 6°C Polar icecaps shrink Oceans rise 15 feet (150 if E Antarctic falls in) – Low countries, islands, cities swamped – 100+°F days in Dallas: 19 increases to 87 – US farmland dries up, Canada thaws out – Mosquitoes, tsetse flies spread disease Has the greenhouse effect already started? Assess the following statements: Carbon dioxide contributes to an elevated global temperature. Concentration of carbon dioxide has been increasing over the past century The increase in atmospheric carbon dioxide over the past century is a consequence of human activity There has been an increase in average global temperature during the past century. Carbon dioxide and other gases generated by human activity are responsible for this temperature increase The average global temperature will continue to increase as anthropogenic emissions of greenhouse gases increase. What can be done? Those that answer this question can be categorized into one of three categories: Must act NOW! Study it more. Don’t act b/c it is inevitable … “Must act Now” Dr. Stephen Schneider (Stanford) “… Is this nature being perverse or is it us? The only way to prove for sure is to hang around another 10, 20, or 30 more years, when the evidence would be overwhelming. But in the meantime, we’re conducting a global experiment. And we’re all in the test tube. “ Source – New York Times, December 1997 Further Study William O’Keefe, CEO of the American Petroleum Institute “ I do not agree that it’s a foregone conclusion that there’s going to be significant climate change if we don’t take dramatic action now. We also have to reduce the scientific uncertainties. We should not base policy on worst-case scenarios.” Dr. Michael Oppenheimer, Environmental Defense Fund “Scientific uncertainties, which are substantial, of course, are not a reason to put off action. In fact, we have only one Earth to experiment on.” Solutions In contrast to the above mentioned groups – there are activists – do something NOW and do it FAST! Add sulfate aerosols in the atmosphere – Mt. Pinatubo in 1991 Fertilize southern oceans in with Iron to increase growth of phytoplankton MIT scientists propose capturing CO2 and pumping it into the ocean depths. Princeton Scientists – pump CO2 underground What can you do? Conclusions Human actions may have long term global impact Impact may take decades to reverse Actions require knowledge, thought, compassion, wisdom Even in the absence of threats like global warming, solutions to this problem would result in sound, prudent, and responsible stewardship of our planet.