"Hottest September in satellite record; new daily high temperature records outpace record lows by 5-to-1"
ENDLESS SUMMER: September was the hottest on record globally in the RSS satellite dataset. In this country, the record-smashing temperatures in Southern California got most of the attention (see “No on Prop 23: It’s getting HOT out here!“)
But, as Steve Scolnik of CapitalClimate reports, “that event was just one of literally thousands of daily high temperature records set in the U.S. during September,” continuing a trend that has persisted for almost the entire year.
I like the statistical aggregation across the country, since it gets us beyond the oft-repeated point that you can’t pin any one record temperature on global warming. If you want to know how to judge whether the 5.2-to-1 ratio for September is a big deal, here’s what a 2009 National Center for Atmospheric Research study found for “1,800 weather stations in the 48 contiguous United States” over the past six decades (see “Record high temperatures far outpace record lows across U.S.“):
In September, daily high temperature records numbered nearly 2400, roughly 1/3 above the previous monthly high for the year, slightly less than 1800 in April. With only 459 daily low temperature records, the ratio of heat records to cold records was 5.2:1, the highest for any month since April’s 6.1:1 dominated the spring statistics. The year-to-date ratio has now risen to 2.6:1. Every month this year from March onward has had at least twice as many heat records as cold records, except for May, when the ratio was 1.4:1.
September also had a large number of record high minimum temperatures (1,286) vs. low maximums (557), a ratio of 2.3:1.
NCAR explained their findings this way:
Spurred by a warming climate, daily record high temperatures occurred twice as often as record lows over the last decade across the continental United States, new research shows. The ratio of record highs to lows is likely to increase dramatically in coming decades if emissions of greenhouse gases continue to climb.
“Climate change is making itself felt in terms of day-to-day weather in the United States,” says Gerald Meehl, the lead author and a senior scientist at the National Center for Atmospheric Research (NCAR). “The ways these records are being broken show how our climate is already shifting.”
I also love the chart below, via Weather historian Christopher C. Burt. His post at Weather Underground, “The Remarkable Summer of 2010,” concludes, “it is probable that no warmer summer in the Northern Hemisphere has ever been experienced by so many people in world history.”
On the other hand, the global record temperatures we’re seeing now are especially impressive because we’ve been in “the deepest solar minimum in nearly a century.” It’s just hard to stop the march of manmade global warming, other than by sharply reducing greenhouse gas emissions, that is.
Tom Peterson, Chief Scientist for NOAA’s National Climatic Data Center, said of the hot U.S. spring, “We’re getting a dramatic taste of the kind of weather we are on course to bequeath to our grandchildren.” But a new analysis by NASA’s James Hansen published last week concluded, “Given the association of extreme weather and climate events with rising global temperature, the expectation of new record high temperatures in 2012 also suggests that the frequency and magnitude of extreme events could reach a high level in 2012” — see Hansen: Would recent extreme “events have occurred if atmospheric carbon dioxide had remained at its pre-industrial level of 280 ppm?” The “appropriate answer” is “almost certainly not.” So 2012 may feel a lot like 2010.
For new readers, here’s the caption on the top figure:
Total number of daily high and low temperature records set in the U.S. for spring 2010 (March-April-May) and monthly from June through September 2010, data from NOAA National Climatic Data Center, background image © Kevin Ambrose. Includes historical daily observations archived in NCDC’s Cooperative Summary of the Day data set and preliminary reports from Cooperative Observers and First Order National Weather Service stations. All stations have a Period of Record of at least 30 years.
- Labor Day 2060: Endless summer
- How hot is it? So hot that June “breaks the record for the warmest average temperature observed for any calendar month in Miami”
- Masters: “It appears that this year’s record [sea surface temperatures] have significantly expanded the area over which major hurricanes can exist over the Atlantic.”
- NASA: The 12-month running mean global temperature has reached a new record in 2010 “” despite recent minimum of solar irradiance: “We conclude that global temperature continued to rise rapidly in the past decade” and “there has been no reduction in the global warming trend of 0.15-0.20°C/decade that began in the late 1970s.”