Joseph Romm: Mother Nature is Just Getting Warmed Up: June 2011 Heat Records Crushing Cold Records by 13 to 1

Mother Nature is Just Getting Warmed Up: June 2011 Heat Records Crushing Cold Records by 13 to 1

by Joe Romm, Climate Progress, June 11, 2011


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 20-60 years if atmospheric greenhouse gas concentrations continue to increase, according to a new climate study by Stanford University scientists….

“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,

That’s from the Stanford release for a new Climatic Change study (PDF here).  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.”

As a taste of things to come, much of the United States has just been hit by a monster heat wave. Steve Scolnik at Capital Climate analyzed the data from NOAA’s National Climatic Data Center (NCDC) and found, “U.S. heat records in the first 9 days of June have outnumbered cold records by an eye-popping ratio of 13 to 1" (1,609/124):

Monthly total number of daily high temperature and low temperature records set in the U.S. for June 2010 through June 9, 2011, data from NOAA.

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 13-to-1 ratio for the first 9 days of June is a big deal, here’s what a 2009 National Center for Atmospheric Research study found over the past six decades (see “Record high temperatures far outpace record lows across U.S."):

This graphic shows the ratio of record daily highs to record daily lows observed at about 1,800 weather stations in the 48 contiguous United States from January 1950 through September 2009. Each bar shows the proportion of record highs (red) to record lows (blue) for each decade. The 1960s and 1970s saw slightly more record daily lows than highs, but in the last 30 years record highs have increasingly predominated, with the ratio now about two-to-one for the 48 states as a whole.

NCAR explained their 2009 findings in a news release:

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.”

The scientific paper itself is here (subs. req’d).  And NCAR posted a video of lead author Meehl discussing his findings here.  The study looked into the future and found that “if nations continue to increase their emissions of greenhouse gases in a ‘business as usual’ scenario, the U.S. ratio of daily record high to record low temperatures would increase to about 20-to-1 by mid-century and 50-to-1 by 2100.”

So the 13-to-1 ratio for early June 2011 is indicative of a major heat wave.

Let’s go back to the new Stanford study, “Observational and model evidence of global emergence of permanent, unprecedented heat in the 20th and 21st centuries.”  The release notes the severe impact of even moderate warming:

This dramatic shift in seasonal temperatures could have severe consequences for human health, agricultural production and ecosystem productivity, Diffenbaugh said. As an example, he pointed to record heat waves in Europe in 2003 that killed 40,000 people. He also cited studies showing that projected increases in summer temperatures in the Midwestern United States could reduce the harvest of staples, such as corn and soybeans, by more than 30%.

Diffenbaugh was surprised to see how quickly the new, potentially destructive heat regimes are likely to emerge, given that the study was based on a relatively moderate forecast of greenhouse gas emissions in the 21st century.

“The fact that we’re already seeing these changes in historical weather observations, and that they match climate model simulations so closely, increases our confidence that our projections of permanent escalations in seasonal temperatures within the next few decades are well founded,” Diffenbaugh said.

The study itself isn’t online yet, but Diffenbaugh sent me a copy.  It concludes:

First, imminent, permanent emergence of unprecedented heat in the tropical regions is likely to result in substantial human impact, particularly given previous humanitarian crises associated with severe heat, and the synergies between environmental and development challenges. Second, the fact that areas of the United States, Europe and China also show permanent emergence by the mid-21st century highlights the fact that nations with developed and emerging economies are also likely to face unprecedented climate stresses even with the relatively moderate warming expected over the next half-century. The fact that global climate models are able to capture the observed intensification of extreme heat globally and over many regions strengthens confidence in the model projections. However, where model biases do exist, they predominantly serve to decrease occurrence of unprecedented heat. Further, actual GHG emissions over the early 21st century have exceeded those projected in the SRES scenario used here, suggesting that our results could provide a conservative projection of the timing of permanent emergence of an unprecedented heat regime.

The model biases make the results more conservative.  So does the choice of emission scenario.

As is common in such analyses, the authors based their simulations on the ‘middle of the road’ emission scenario, A1B. In 2100, A1B hits about 700 ppm with average global temperatures “only” about 3 °C (5 °F) warmer than today. In fact, on our current emissions path, a 3 °C temperature rise will happen much sooner (see Hadley Center: “Catastrophic” 5-7 °C  warming by 2100 on current emissions path and M.I.T. doubles its 2095 warming projection to 10 °F — with 866 ppm and Arctic warming of 20 °F).   And remember, the  worst-case scenario is that this happens by mid-century (see Royal Society special issue details ‘hellish vision’ of 7 °F (4 °C) world — which we may face in the 2060s!).

I haven’t yet interviewed Diffenbaugh about his new study, but I interviewed him for my book, Hell and High Water, and in 2008 wrote about his earlier work in a post I reprint below:

When can we expect very high surface temperatures?

Sure glacier melt, sea level rise, extreme drought, and species loss get all the media attention — they are the Britney Spears, Paris Hilton, and Barack Obama of climate impacts. But what about good old-fashioned sweltering heat? How bad will that be? Two little-noticed studies — one new, one old — spell out the grim news.

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.

The peak temperature analysis comes from a Geophysical Research Letters paper published two weeks ago that focused on the annual-maximum “once-in-a-century” temperature. Researchers looked at the case of a (mere) 700 ppm atmospheric concentrations of CO2, the A1b scenario, with total warming of about 3.5 °C by century’s end. The key scientific point is that “the extremes rise faster than the means in a warming climate.”

The results, depicted above (in °C), are quite remarkable, especially when you consider that this is, again, just the A1B scenario.  On our current emissions path, these record temperatures could be seen closer to 2060 than 2100:

… values in excess of 50 °C [122 °F] in Australia, India, the Middle East, North Africa, the Sahel, and equatorial and subtropical South America.

As you can see from the map, extreme temperature peaks are only slightly lower over large parts of this country. The study notes:

Such temperatures, if lasting for some days, are life threatening and receive relatively little attention in the climate change debate.

So now the question is, has anybody done an analysis of what global warming could do to intense heat waves that last very long times, weeks or months? The answer is yes, and the results of that study are more worrisome — and it also received relatively little attention.

The November 2005 study in the Proceedings of the National Academy of Sciences, “Fine-scale processes regulate the response of extreme events to global climate change,” found that “peak increases in extreme hot events are amplified by surface moisture feedbacks.” The study looked at the A2 scenario (about 850 ppm in 2100) in the second half of this century (from 2071 to 2095). It examined temperature rise projections, plus “fine-scale processes,” such as how local warming is affected by loss of snow cover and loss of soil moisture. I interviewed the lead author, Noah Diffenbaugh, of Purdue University, for my book.

Houston and Washington, DC, would experience temperatures exceeding 98 °F for some 60 days a year. Oklahoma would see temperatures above 110 °F some 60-80 days a year. Much of Arizona would be subjected to temperatures of 105 °F or more for 98 days out of the year – 14 full weeks. We won’t call these heat waves anymore. As Diffenbaugh told me, “We will call them normal summers.”

And again, that’s not even the worst case, since it’s “only” based on 850 ppm.

The definitive NOAA-led U.S. climate impact report from 2010 warns of scorching 9-11 °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.  Again, it’ll just be the “normal” climate.

On our current emissions path, we may well exceed the A2 scenario and hit A1F1, 1,000 ppm (see here).  In a terrific March presentation, Climate scientist Katherine Hayhoe has a figure of what the A1F1 would mean (derived from the 2010 NOAA-led report):

Mother Nature is just warming up.

The time to act is yesterday.

Related post:

• Science stunner — On our current emissions path, CO2 levels in 2100 will hit levels last seen when the Earth was 29 °F (16 °C) hotter:  Paleoclimate data suggests CO2 “may have at least twice the effect on global temperatures than currently projected by computer models”

http://thinkprogress.org/romm/2011/06/11/242903/mother-nature-is-just-getting-warmed-up-june-heat-records/#more-242903