Record High May Temperatures in US Continue to Outpace Record Lows

US surface temperatures May 26, 2010 image

images via Climate Capital

April turned out to be the hottest on record globally, and South Asia is in the midst of a heatwave that is the hottest since modern records began two hundred years ago. Closer to home, as Capital Climate points out, the National Climatic Data Center reports for the past three months in the US new record highs are outpacing record lows by at least two-to-one. Looking at a narrow time period at the end of May is indicative of the broader trend, if showing even more extreme results than the average:

Updated figures for the entire month show heat records outnumbering cold records in May by over 40% (1054 vs. 748). For the week ending May 28, the ratio was almost 3:1. The number of heat records on May 26 has increased to 115 vs. only 7 cold records.

2010 record temperature ratio chart

A Normal Record Ratio Over Time is 1:1
If you're shrugging your shoulders right now, wondering what the big deal is, consider that over time the expected ratio for new record highs and record lows is about 1:1. However, over the past decade that ratio has been about 2:1, with data indicating that part of the issue is that nights aren't cooling as much as they used to.

Over the past century the ratio of record highs to lows slightly exceed 1:1 in the 1950s, returned to about 1:1 in the 60s and 70s, and then began increasing again in the 1980s.

Under a business-as-usual climate change scenario, this ratio could hit 20:1 by 2050 and 50:1 by 2100. Even under a scenario where emissions are constrained, by 2050 we could still be experiencing eight times as many new record highs and record lows.

hat tip: Climate Progress
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More on Global Climate Change:
US Record High Temperatures Double Record Lows Over Past Decade
Record Highs Beating Record Lows in US by 2-to-1, Redux
Warmest April, Ever - NOAA Releases New Global Temperature Data

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