Multiple heat waves cap Earth’s warming trend — Record highs outpace record lows
Climatewire, July 9th, 2010 — This time, the heat is really on. From Boston to Washington, D.C., temperatures have soared to 100 degrees or more in recent days, stressing electrical grids, scrambling rail transportation and prompting the swift creation of cooling centers for those who lack air conditioning. Central Canada, portions of the Middle East and China are also coping with searing heat. Overall, according to the National Oceanic and Atmospheric Administration, the combined global land and ocean temperatures from January to May were warmer than in the same period in any year on record — a comparison that reaches back to the 1880s. But how much of the heat can be blamed on climate change? “We can’t say that one individual or even two heat waves are due to global warming,” said David Easterling, a climatologist with NOAA’s National Climatic Data Center. “But what we can say is that warming temperatures do increase the probability of a heat wave.” Scientists have documented a pronounced warming trend in the United States and around the world over the last several decades. In its 2007 report, the Intergovernmental Panel on Climate Change concluded with 90 percent certainty that human-caused greenhouse gas emissions have been the primary factor in Earth’s overall temperature rise since 1950. Meanwhile, the World Meteorological Organization said late last year that the 2000-2009 decade appears to be the warmest since record-keeping began in the 1850s. Easterling said studies also show an increase in the occurrence of heat waves in the United States since 1960. One recent analysis he published with colleagues at the National Center for Atmospheric Research, Climate Central and the Weather Channel concluded that climate change is skewing the proportion of record high temperatures to record low temperatures in the continental United States. Record highs outnumbered record lows 2-to-1 over the last decade, and the study — published in Geophysical Research Letters last year — predicted that disparity could balloon to 20-to-1 by the end of this century without sharp curbs on greenhouse gas emissions. …
