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�c � � �'�r.� � � �+�#' Global Warming: The Facts What is global warming? . The change in Earth's temperature caused by the burning of oil, coal and natural gas and changes in land surface properties. . Greenhouse gasses (Carbon Dioxide, Methane, Chlorofluorocarbons and Nitrous Oxide and aerosols trap heat in the atmosphere. • Snow and ice reflect 90% of the heat that hits them hack into the atmosphere, but water absorbs 90% of the radiation that hits it. * Carbon Dioxide (COZ) is the most important greenhouse gas. The increased concentration in the atmospheric concentration is due to use of fossil fuels, with land use playing a smaller role. What is the evidence that global warming is happening? • 11 of the last 12 years have been among the 12 warmest years on record + The concentrations of all of the greenhouse gasses mentioned above have increased since the industrial revolution. The COz concentration has gone from 280 parts per million (ppm) to 379 ppm, and the methane concentrationfrom .$ to 1.7 ppm. ■ The average atmospheric water vapor content has increased since the 1980s over land and sea, because warmer air can hold more water vapor. t The average temperature of the global ocean has increased since 1961 to the depth of at least 3 kilometers, causing the water to expand and sea level to rise. * The number of category 4 and 5 hurricanes has doubled in the last 30 years. # Mountain glaciers and snow cover have declined, and the rate of inelting is speeding up; the flow of ice from glaciers in Greenlandhas more that doubled in the past decade. t At least 279 species of plants and animals have reacted to the change in temperatures by moving closer to the Qoles. What will be the effects oi�l�ba� warming? . For the next 2 decades a warming of about 0.2" C per decade is expected/ • Continued greenhouse gas emissions at or above current rates would cause �€zrther warming and induce many changes in the climate that are very lil{ely to be greater that those observed during the 20��' century. • Models that do not take into account rapid changes in ice flow predict a rise in sea level of up to 59 cm.in 90 years; if there is a loss in the ice shelfin Greenland or Antarctica, the global sea level could rise up to 20 feet. • Hot extremes, heat waves and heavy precipitation events will become more frequent. . Droughts and wildfires will occur more often. What can we do? . Many steps are individual, Iilce energy efficient appliances and light bulbs, hybrid cars and carpooling, recycling, buying green power, and buying environmentally friendly products. . The Kyoto Treaty is an international treaty that is designed to reduce the emission of greenhouse gasses. It calls on industrialized countries to reduce their combined emissions of six major greenhouse gasses by 2012 to their levels in 1990. . The United States government hasn't signed this treaty, hut individual cities can take the initiative to do this by themselves by joining the cool cities campaign. Sources: The Int�rg4vernrr�e�ltal Panel on Climate Change Summary for policy makers; www.ipcc.ch/, www.climatecrisis.net, C}t�pdsi�tg vie�oints- Global Warmin�, edited by Cynthia A. Bily, Greenhaven Press, 2006.