In brief: Study says no global warming hiatus

     Despite the fact that numerous scientists have said humans contribute to global warming, various politicians have raised questions about whether that is true. This is more than a theoretical debate: It is the central issue in determining which policies the government uses to address the problem.
     At the same time, recent science suggests that climate change is relentless. A new paper by National Oceanographic and Atmospheric Administration researchers finds that global warming has not slowed down--as some believe.
     In research released June 4, scientists explored an apparent decrease in the upward trend of global surface temperatures since 1998, dubbed the “global warming hiatus." As it turns out, that “hiatus” may not have been a hiatus at all. Here is the rundown.    

     The paper: The research was published in the journal Science and is titled, “Possible artifacts of data biases in the recent global surface warming hiatus.” Lead authors include Thomas R. Karl of the National Oceanographic and Atmospheric Administration's National Centers for Environmental Information.

     The basics: Previously, the Intergovernmental Panel on Climate Change had concluded that the global surface temperature “has shown a much smaller increasing linear trend over the past 15 years [1998-2012] than over the past 30 to 60 years.” 

      How is climate change measured? Numbers used in long-term global temperature analysis “primarily involve surface air temperature observations taken at thousands of weather observing stations over land, and for coverage across oceans, the data are sea surface temperature (SST) observations taken primarily by thousands of commercial ships and drifting surface buoys,” the paper explained. “These networks of observations are always undergoing change.”

     How is the network changing? There is “an increasing amount of ocean data from buoys, which are slightly different than data from ships,” the paper said. There is also an increasing amount of “ship data from engine intake thermometers, which are slightly different than data from bucket sea-water temperatures.” There is also an increase in “land-station data that enables better analysis of key regions that may be warming faster or slower than the global average.”

     Why does that matter? Several studies have examined the differences between buoy- and ship-based data, the study said, and “the ship data are systematically warmer than the buoy data. This is particularly important, as much of the sea surface is now sampled by both observing systems, and surface-drifting and moored buoys have increased the overall global coverage by up to 15 percent.”
     Generally, “buoy data have been proven to be more accurate and reliable than ship data,” according to the report.
      There have also been improvements in the calculation of land surface air temperatures. 

     Conclusions: Newly corrected global surface temperatures “do not support the notion of a global warming ‘hiatus,’” the report said. “There is no discernible (statistical or otherwise) decrease in the rate of warming between the second half of the 20th century and the first 15 years of the 21st century. “
     Read the report here.

     Related:

     Study: Heat waves sparked by climate change

     Doing the Math: Scientists and global warming

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