| Summary: | Climate change is no longer an issue for consideration in the future. Climate changes are being observed all over the U.S., from Miami to Arctic Alaska, and from the top of our atmosphere to the depths of our oceans. This report documents changes already observed and those projected for the future. CO2 in the atmosphere has increased over 40% since the industrial Revolution, while methane and nitrous oxide emissions from agriculture etc. also add heat-trapping gases. Sensors on the satellites, however, have measured the sun's output and found no overall increase during the past half century. Absent human activity, global climate would have cooled slightly over the past 50 years - cooling has occurred in the stratosphere while warming has taken place near the surface. Short-term fluctuations in the natural variations background have slowed the rate of surface air temperature rise due to cyclic changes in the oceans and the sun's energy output, as well as a series of small volcanic eruptions. U.S. average temperature has increased by 1.3 - 1.9 F since 1895, mostly since 1970, and are projected to rise another 2 - 4 F over the next few decades. The most recent decade was the nation's and the world's hottest on record, and 2012 was the hottest year in the continental U.S. In general, temperatures are rising more quickly in the north - where vast quantities of methane are still frozen. In some regions, higher temperatures and droughts have contributed to conditions leading to larger wildfires and longer fire seasons, while in others (eg. northeast and north-central areas) very heavy precipitation has significantly increased.
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