Surprise: Over the last decade, the US cooled

Anthony Watts Meteorologist and Climate Blogger

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?

Even worse, there may be more cooling than meets the eye due to adjustments that have been made in the data. For example, take the year 1934, long considered to be the hottest year in U.S. history. When you go back and look at data from NASA (which also uses the NOAA/NCDC data, like the new Berkeley data does), you find that things have changed: The past temperature has been modified.

Take, for example, a 1999 report from Dr. James Hansen at NASA’s Goddard Institute for Space Studies (GISS). As Hansen said at the time:

The U.S. has warmed during the past century, but the warming hardly exceeds year-to-year variability. Indeed, in the U.S. the warmest decade was the 1930s and the warmest year was 1934.

I’ve prepared a before-and-after graph comparing the U.S. temperature values that GISS used in its 1999 report with the values it used in its 2011 report. The juxtaposition is revealing:

GISS writes now of the bottom figure:

Annual Mean Temperature Change in the United States

Annual and five-year running mean surface air temperature in the contiguous 48 United States (1.6% of the Earth’s surface) relative to the 1951-1980 mean. [This is an update of Figure 6 in Hansen et al. (1999).]

So clearly, the two graphs are linked, and 1998 and 1934 have swapped positions for the “warmest year.” 1934 went down by about 0.3°C while 1998 went up by about 0.4°C, for a total change of about 0.7°C. Unless you live in an Orwellian world of science, how does one justify modifying the temperature history of the past?

If this were a graph of stock performance data given to investors as a prospectus and such shenanigans were discovered, the Securities and Exchange Commission would be launching an investigation. Yet, our own government is spending billions on climate change research and related programs, seemingly accepting such modified historical data without question.

And they wonder why climate skeptics don’t trust the surface temperature data. How can we when modifying the past is considered an acceptable practice by keepers (NOAA and NASA) of the historical temperature record of the United States?

Anthony Watts operates the most visited blog on climate science in the world, WattsUpWithThat.com.