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On cue: United States registers hottest month ever


His timing is uncanny. Just days after NASA climatologist James Hansen released his latest study pinning the blame for hot summer extremes squarely on the shoulders of humans and our greenhouse-gas emissions, we learn that the United States has just experienced its hottest month. Ever.

The average temperature across the continental United States in July was 77.6 °F (25.3 °C), the US National Oceanic and Atmospheric Administration announced Wednesday. That is 3.3 °F (1.8 °C) above the twentieth-century average and a touch higher than the previous record of 77.4 °F, set in 1936.

But a quick glance at the map above, which shows regional temperature anomalies above the average July temperatures from 1981-2010, shows  that averages aren’t the whole story. Temperatures in parts of the South and West were normal or even below average compared to the last three decades, while parts of the Midwest and the northern Rocky Mountains chalked up readings as much as 8 °F (4.4 °C) above normal. A full-size version of the map is available here.

That we are breaking records set during the Dust Bowl is relevant. At last week’s hearing on Capitol Hill, sceptical lawmakers cited the fact that many record temperatures were set during the 1930s as evidence against the existence of global warming. But although nobody denies that the 1930s were hot, this logic misses the point.

One expects to set record temperatures in the early days of a temperature record. The first reading will be a record high and a record low, and the second will necessarily be one or the other. And then over time, in a stable climate, record temperature readings will diminish. This is simple statistics. But as illustrated by a graphic presented at last week’s Senate hearing by Christopher Field, co-chair of the Intergovernmental Panel on Climate Change’s second working group on adaptation, we continue to set new temperature records with alarming frequency. And most of them, just to be clear, are on the warm side.


For the record, Senate Majority Leader and Nevada Democrat Harry Reid has formally broached the idea of bringing up some kind of climate legislation in the Senate during the next Congress, assuming Democrats maintain control of the chamber. It’s a rather weak and vague commitment, to be sure, extracted by a Greenwire reporter who was apparently hounding the senator during a tour of the exhibitions at the National Clean Energy Summit. But still, given the state of the debate of late, it’s worthy of note.


CORRECTION: An earlier version of this post implied that the map displayed temperature anomalies above July’s twentieth-century average; in fact, it displays temperature anomalies above average July temperatures from 1981-2010.




  1. Report this comment

    James Dwyer said:

    Regarding the correction, indicating that the map illustrates July’s regional temperature variation relative to average July temperatures from 1981-2010, wouldn’t it have been more informative to display the variation relative to the 20th century average? The average temperatures between 1981 and 2010 are thought to represent years affected by global warming, not a baseline!

    Regarding the statement, “That we are breaking records set during the Dust Bowl is relevant,” NOAA pitched that story in its National State of the Climate monthly report for July, 2012 retrieved today. Actually, only the July average temperature for the 48 contiguous states exceeded the record previously held during the Dust Bowl. Virginia was the only state that set a new record high average temperature for the month.

    The states most affected by the Dust Bowl conditions in the early-mid 1930s did not collectively approach record setting conditions in either temperature or rainfall. In fact, while drought conditions certainly exist in many states, no state set new records for low precipitation in July.

    To suggest that July climatic conditions were comparable to those of the Dust Bowl is a blatant misrepresentation. Please review the conditions suffered by Americans during the Dust Bowl for comparison.

    There is no reasonable doubt that the long term climate is significantly changing and that it will soon become a serious problem. However, to blatantly misrepresent the data is irresponsible. I for one remember what happened to the little boy who cried ‘wolf!’ too often – what will we do when we really are once again experiencing Dust Bowl conditions?

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