Opinion

Surprise: Over the last decade, the US cooled

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Anthony Watts
Meteorologist and Climate Blogger
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      Anthony Watts

      Mr. Watts operates the most visited blog on climate science in the world, <a href="http://www.wattsupwiththat.com"> Watts Up With That?</a>, now with over 75 million visits. He has spent 30 years on air in radio and television as a weather forecaster, and still does daily radio broadcasts. In 2007, he founded the surfacestations.org project, which with the help of volunteers nationwide found that only 1 in 10 of the weather stations used for monitoring climate in the USA met the government's own standards for station siting quality. He also operates a weather technology business, embraces energy efficiency with solar power on his home and drives an electric car.

There’s been a lot of buzz and conflicting reports over what the new Berkeley Earth Surface Temperature (BEST) data actually says. Depending on whose pronouncements you read, the data reveals that there’s been a “slowing down,” a “leveling off,” a “standstill” or a “slight rise” in global warming over the past decade.

So I decided to look at the data myself. I created regional breakdowns of the winter, summer and annual data for the continental U.S.

Below is a map  with graphs for winter temperatures (December through February) and trends from 2001 to 2011. Note that every region of the United States has a negative temperature trend for the last decade:

Here’s the same map/graph combination for summer temperatures (June through August) and trends from 2001 to 2011. Note that five of the nine regions have a negative summertime temperature trend:

I’m told on my blog, WattsUpWithThat, that people who grow tomatoes in their gardens, especially in the Western U.S., have noted the difference in summer temperatures, saying “tomatoes have no reason to lie.” People in Great Britain have reported similar results, saying summers have gotten cooler and growing garden tomatoes has become a lost cause.

Another surprise is the annual yearly mean temperature trend for the last decade in the United States. Since 2011 is not yet complete, I’ve plotted the mean temperature trend from 2000 to 2010:

Only one of nine regions (the Northeast) has a positive decadal trend for its annual mean temperature.

This data is from the National Climatic Data Center (NCDC). Note that I have not adjusted it or even self-plotted it in any way. You can replicate what I’ve found yourself. The output graphs and trend numbers are from NCDC’s publicly available “Climate at a Glance” database interface, and these can be fully replicated by anyone simply by going here and choosing “regions.”

I find the fact that summer temperature trends were negative in five of the nine regions interesting. But most importantly, the trend for the continental United States for the past 10 years is not flat, but cooling. The trend line for the lower 48 states looks like this for the same period when we plot the annual mean temperature data for 2001-2010:

So according to NOAA’s National Climatic Data Center, it seems clear that for at least the last 10 years, there has been a cooling trend in the annual mean temperature of the continental U.S. While this is not the standard 30-year period used by climatologists to determine climate for an area, it does beg the question: If carbon dioxide is in control of our climate, as many advocates claim, how could this happen?