Wednesday, March 6, 2013

How Both Sides Of The Global Warming Debate Use Same Data To Make Their Case

In a post on by contributor James Taylor published on  3/6/13, he stated that "global temperatures are essentially the same today at they were in 1995". The statement directly contradicts a claim made in a post on published on 2/27/13 that indicates "climate change is making the world, on average, a warmer place. The United States is no exception".

The reason that both claims can be supported is that by cherry picking the starting point on a step chart it is possible to support vastly different conclusions.

As shown in the chart below, adding a trend line to U.S. temperatures going back to 1900 shows a steady rise . However, graphing a line from 1995  to 2012 indicates that the U.S. temperature has remained relatively unchanged.

The above chart offers a good illustration of how cherry picking the starting point on a step chart can dramatically impact the slope of a trend line. The case made by global warming skeptics that the earth is not warming would be stronger if they were able to make their case without cherry picking the warm years of 1995, 1998, 2002, 2007, or 2010. It could well be that Mr. Taylor is correct that the earth's temperature has stopped rising. However, it seems much more likely that he has disingenuously cherry picked a starting point that allows him to make his case. Using a 17 year period to measure a trend seems rather unusual unless talking about cicadas.

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