How hot is it? It’s so hot that all-time records are being set in June: “Nashville has reached its hottest temperature on record…109 degrees at 314 pm. The previous all time record was 107 from July 27th and 28th of 1952.”

UPDATE: Meteorologist Dr. Jeff Masters has more all-time heat records:

109° Columbia, SC (old record 107° on two previous occasions)
109° Cairo, IL (old record 106° on 8/9/1930)
108° Paducah, KY (ties same on 7/17/1942
106° Chattanooga, TN (ties same on 7/28/1952)
105° Raleigh, NC (ties same on 8/21/2007 and 8/18/1988)
105° Greenville, SC (old record 104° 8/10/2007 although 106° was recorded by the Signal Service in July 1887)
104° Charlotte, NC (ties same on 8/9 and 10/2007 and 9/6/1954)
102° Bristol, TN (ties same on 7/28/1952-this site now known as ‘Tri-State Airport’)
109° Athens, GA. This is just 1° shy of the Georgia state record for June of 110° set at Warrenton in 1959.

Here is a great graphic via Capital Climate:


The U.S. surface temperature map from Unisys at 4 pm, June 29,2012, shows 100° temperatures stretching almost continuously from California eastward to the Carolinas.

NBC Meteorologist Bill Karins said on Friday , “We’ve never really seen a heat wave like this in the month of June.” Sadly, in a few decades this will just be considered a normal June (see below).

How hot is it? It is so hot that NBC Washington’s Chief Meteorologist, Doug Kammerer, explained on air “If we did not have global warming, we wouldn’t see this.”

Like a baseball player on steroids, our climate system is breaking records at an unnatural pace (see “March Came In Like A Lamb, Went Out Like A Globally Warmed Lion On Steroids Who Smashed 15,000 Heat Records”).

As Climate Central explains in its post, “Scorching June Heat Wave Puts 50 Million in U.S. on Alert”:

During the June 22-to-28 period, there were 2,132 warm temperature records set or tied in the U.S., compared to 486 cold temperature records. This includes 267 monthly warm temperature records, and 54 all-time warm temperature records.

For the year-to-date, warm temperature records have been outpacing cold temperature records by about 7-to-1.

In a long-term trend that demonstrates the effects of a warming climate, daily record-high temperatures have recently been outpacing daily record-lows by an average of 2-to-1, and this imbalance is expected to grow as the climate continues to warm. According to a 2009 study, if the climate were not warming, this ratio would be expected to be even. Other studies have shown that climate change increases the odds of extreme heat events and may make them warmer and longer lasting.

All-time records set Thursday included several in Kansas, where Norton Dam recorded a high of 118°F, beating the old record of 113°F set just a few days earlier. Dodge City, Kan., set a daily high temperature record with a mark of 108°F. That came one day after that town recorded its all-time highest temperature of 112°F, breaking the old record of 110°F, which had been recorded just two days earlier, on June 26.

Since the science of attributing extreme events to global warming is still emerging, scientists still disagree to what extent a specific event like this heat wave is driven by global warming. But two of the leading experts explain at RealClimate why even small shifts in average temperature mean “the probability for ‘outlandish’ heat records increases greatly due to global warming.” Furthermore, “the more outlandish a record is, the more would we suspect that non-linear feedbacks are at play – which could increase their likelihood even more.”

Here’s a Stanford release for Climatic Change study (PDF here) I wrote about last year:

Stanford climate scientists forecast permanently hotter summers

The tropics and much of the Northern Hemisphere are likely to experience an irreversible rise in summer temperatures within the next 20 to 60 years if atmospheric greenhouse gas concentrations continue to increase….

“According to our projections, large areas of the globe are likely to warm up so quickly that, by the middle of this century, even the coolest summers will be hotter than the hottest summers of the past 50 years,” said the study’s lead author, Noah Diffenbaugh, The study, based on observations and models, finds that most major countries, including the United States, are “likely to face unprecedented climate stresses even with the relatively moderate warming expected over the next half-century.”

I interviewed Diffenbaugh for my book, Hell and High Water, and in 2008 wrote about his earlier work in a post titled, “When can we expect very high surface temperatures?”

Bottom line: By century’s end, extreme temperatures of up to 122°F would threaten most of the central, southern, and western U.S. Even worse, Houston and Washington, DC could experience temperatures exceeding 98°F for some 60 days a year. And that’s not even the worst case, since it’s “only” based on the A2 scenario, 850 ppm.

The peak temperature analysis comes from a Geophysical Research Letters paper that focused on the annual-maximum “once-in-a-century” temperature. The key scientific point is that “the extremes rise faster than the means in a warming climate.”

The definitive NOAA-led U.S. climate impact report from 2010 warns of scorching 9 to 11°F warming over most of inland U.S. by 2090 with Kansas above 90°F some 120 days a year with 850 ppm. By 2090, it’ll be above 90°F some 120 days a year in Kansas — more than the entire summer. Much of Florida and Texas will exceed 90°F half the days of the year. These won’t be called heat waves anymore. It’ll just be the “normal” climate.

And remember, high heat means dry areas become drier and humid areas become intolerable.

On our current emissions path, we may well exceed the A2 scenario and hit A1FI, 1000 ppm (see here). In a 2010 presentation, Climate scientist Katherine Hayhoe has a figure of what the A1FI would mean:


Mother Nature is just warming up.

The time to act is yesterday.