Claim: The jury is still out about global warming

Claire Todd, Visiting Assistant Professor of Geosciences and Environmental Studies

Recent events such as the snowstorms in the eastern United States have caused some to question whether or not global temperatures are increasing.

To address these questions, we can turn to the instrumental temperature record, a record of temperatures measured directly by humans for the past 130 years. These measurements, made with thermometers and, more recently, satellites, are averaged to calculate one global mean temperature per year. Simply put, the instrumental temperature record is astonishing. Twenty of the warmest global mean annual temperatures have occurred in the last 25 years, with 2005 being the warmest year. 2009, 2007, 2006, 2003, 2002, and 1998 are all tied for second warmest. The 2000s were the warmest decade on record, and each of the preceding three decades was warmer than the one before it (Hansen et al., 2010).Satellite data document temperature increases on both ocean and land surfaces, and in both urban and rural environments. Scientists expect climate patterns to continue to fluctuate from year-to-year, such as the El Nino – La Nina climate oscillation, but global mean temperatures are expected to rise 0.2 to 1.0 º F per decade through the 21st century (Mote et al., 2009; IPCC, 2007). In the Pacific Northwest, increased temperatures will bring rising sea levels, reduced snowpack and more extreme weather patterns. Bottom line: Direct measurements deliver a clear verdict: global temperatures are increasing.

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