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Extreme Weather and Climate Change: The Southeast

 

WHAT WE KNOW

  • On average, the US is 2 degrees F warmer than it was 40 years ago.
     
  • This warmer world is increasing the odds of extreme precipitation,(20,21)in part because a warmer atmosphere can hold more moisture and release more of it during rainstorms and snowstorms.
     
  • Heavy precipitation, both rain and snow, is happening more often than it used to.(10,4)
     
  • Heat-related extreme events are on the rise around the globe. Manmade climate change significantly increased the odds of some specific events, including the killer European heat wave of 2003(6and the Russian heat wave of 2010.(12)
     
  • Even small increases in average temperatures raise the risk of heat waves (6a, 6b), droughts(7)and wildfires.(8)
     
  • Twice as many record highs have been set in the past decade as record lows, in the US.(9)
     
  • By 2050, record highscould outpace record lows by 20 to 1 in the U.S. By the end of the century, the ratio could jump to 100 to 1 if greenhouse gas emissions continue unabated.(9)

Devastating deluges, record floods and deadly heat waves have raised the question of whether there’s a connection between these events and global warming.

The bottom line answer is yes: Heat waves are longer and hotter than they used to be and some regions are suffering from catastrophic drought.  Heavy rains are more frequent and can be more intense and rainfall records have been smashed. These events fit a pattern that climate scientists have longexpected to appear as the result of increased greenhouse gases in ouratmosphere. That doesn’t mean global warming is the only culprit: extreme weather was happening before global warming began. But there’s general scientific agreement that global warming has contributed to a trend toward more intense extremes of heat and precipitation around the world, is partly to blame for specific extreme weather events over the last decade and willcontinue to influence both in the future.

Damage caused by a tornado that touched down in Tuscaloosa, AL

 

 

 

 

 

THE SOUTHEAST 


Spring 2011 Tornadoes

People who live in the southeastern U.S. are no strangers to tornadoes, which tend to strike during the hot, humid days of spring and summer. But the outbreaks that struck in April and May of 2011 were especially numerous and deadly. April had the most twisters of any month since modern records began in 1950, and in May, the deadliest tornado since 1947 killed 161 people in Joplin, Missouri.

You need three things for a tornado to form: 

1.     A warm, unstable atmosphere

2.     Wind shear (winds that change speed and/or direction the higher you go)

3.     Something — a cold front, for example—that triggers thunderstorms

We know that climate change is influencing two of these factors, fueling more atmospheric instability because it’s warming the air temperature(1,3) and adding water vapor to the air(2) which can mean more powerful thunderstorms.

A warming climate, however, might cause wind shear to decrease,(3) but it’s too early to tell. Scientists have not observed clear trends in tornado frequency, strength or geographical distribution, so they can’t say yet whether or not tornado behavior is changing due to global warming.

What happened in 2011:

  • Spring storms were energized by an unusually warm Gulf of Mexico, which provided an ample supply of warm, humid air for storms to draw from.
     
  • Spring 2011 brought several deadly tornado outbreaks to the Southeastern U.S., including the largest in the nation’s history. The 748 twisters that touched down in April were the most ever recorded in a single month and the EF-5 tornado that leveled much of Joplin, Missouri on May 22 killing over 150 people was the country’s deadliest single tornado since modern record-keeping began in 1950. Damage from the storms has been estimated at nearly $12 billion overall, according to the National Climatic Data Center.
     

    Tornado reports during the month of April 2011. Credit: NOAA.

  • The April 14th–April 16th tornado outbreak, which spawned 30 confirmed tornadoes in North Carolina alone, broke records for the single-storm and single-day tornado outbreaks for that state. Another major tornado outbreak, which took place between April 25 and 30, affected several states in the Southeast and the Midwest, killing 321 people. This outbreak caused more than $6.6 billion in insured losses with total losses exceeding $9.0 billion. Damages were especially high because many of the tornadoes struck densely populated areas such as Birmingham, Huntsville and Tuscaloosa Alabama.

Extreme Heat of 2011

In mid July, much of the nation sweltered under a “heat dome” that brought roasting heat and sweltering humidity to much of the eastern two thirds of the country. At its worst, more than 140 million Americans were under a heat advisory or excessive heat warning, with the heat index - a measure of discomfort that combines both heat and humidity and describes how hot it actually feels - reaching levels typical of the area surrounding the Red Sea in Saudi Arabia.

In the Southeast, the August heat was especially brutal:

  • Gainesville, Tallahassee and Tampa, FL; and Columbus and Savannah, GA experienced their hottest August on record.
     
  • Tallahassee, FL; Augusta, Athens, Columbus and Savannah, GA; Charleston and Columbia, SC; and Cape Hatteras, NC suffered through their hottest summers on record. 
  • In July, Cape Hatteras, NC tied its record for the warmest month and Raleigh-Durham, NC had its hottest July ever. 
  • During July, Washington, DC hadits warmest single calendar month in history, including an all-time record high of 105 degrees F at Dulles Airport on July 22. The heat index at Washington’s Reagan National Airport hit 121 degrees F, the second-highest known level since 1980. 
  • On August 4, Charleston, SC set an all-time record high overnight temperature on August 4 of 83 degrees F and Columbia, SC tied its all-time record high overnight temperature of 82 degrees F, first set in 1936. 

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References

(1)Hegerl, G.C., F. W. Zwiers, P. Braconnot, N.P. Gillett, Y. Luo, J.A. Marengo Orsini, N. Nicholls, J.E. Penner and P.A. Stott, 2007: Understanding and Attributing Climate Change. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

(2)Identification of human-induced changes in atmospheric moisture content 
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(3)Trapp, R. J., N. S., Diffenbaugh, and A. Gluhovsky (2009), Transient response of severe thunderstorm forcing to elevated greenhouse gas concentrations, Geophys. Res. Lett., 36, L01703, doi:10.1029/2008GL036203.

(4)Trenberth, K.E., P.D. Jones, P. Ambenje, R. Bojariu, D. Easterling, A. Klein Tank, D. Parker, F. Rahimzadeh, J.A. Renwick, M. Rusticucci, B. Soden and P. Zhai, 2007: Observations: Surface and Atmospheric Climate Change. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

(5a)Stott, P. A., Gillett, N. P., Hegerl, G. C., Karoly, D. J., Stone, D. A., Zhang, X. and Zwiers, F. , 2010: Detection and attribution of climate change: a regional perspective. Wiley Interdisciplinary Reviews: Climate Change, 1: 192–211. doi: 10.1002/wcc.34;

(5b)Meehl, G.A., T.F. Stocker, W.D. Collins, P. Friedlingstein, A.T. Gaye, J.M. Gregory, A. Kitoh, R. Knutti, J.M. Murphy, A. Noda, S.C.B. Raper, I.G. Watterson, A.J. Weaver and Z.-C. Zhao, 2007: Global Climate Projections. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

(6a)Christidis, N., P.A. Stott, and S. Brown, 2011: The role of human activity in the recent warming of extremely warm daytime temperatures. Journal of Climate
doi:10.1175/2011JCLI4150.1  http://journals.ametsoc.org/doi/abs/10.1175/2011JCLI4150.1

(6b)Human contribution to the European heatwave of 2003 (vol 432, pg 610, 2004) 
Author(s): Stott PA; Stone DA; Allen MR
Source: NATURE  Volume: 436   Issue: 7054   Pages: 1200-1200   DOI: 10.1038/nature04099   Published: AUG 25 2005

(7)Droughtunder global warming: a review 
Author(s): Dai Aiguo
Source: WILEY INTERDISCIPLINARY REVIEWS-CLIMATE CHANGE  Volume: 2   Issue: 1   Pages: 45-65   DOI: 10.1002/wcc.81   Published: JAN-FEB 2011

(8)Detecting the effect of climate change on Canadian forestfires 
Author(s): Gillett NP; Weaver AJ; Zwiers FW; et al.
Source: GEOPHYSICAL RESEARCH LETTERS  Volume: 31   Issue: 18     Article Number: L18211   DOI: 10.1029/2004GL020044   Published: SEP 29 2004

(9)Relative increase of record high maximum temperatures compared to record low minimum temperatures in the U. S. 
Author(s): Meehl Gerald A.; Tebaldi Claudia; Walton Guy; et al.
Source: GEOPHYSICAL RESEARCH LETTERS  Volume: 36     Article Number: L23701   DOI: 10.1029/2009GL040736   Published: DEC 1 2009

(10)Global observed changes in daily climate extremesof temperature and precipitation 
Author(s): Alexander LV; Zhang X; Peterson TC; et al.
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(11)Single-step attribution of increasing frequencies of very warm regional temperatures to human influence
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Source: ATMOSPHERIC SCIENCE LETTERS  Volume: 12   Issue: 2   Pages: 220-227   DOI: 10.1002/asl.315   Published: APR-JUN 2011

(12)Rahmstorf, S. and D. Coumou, 2011, Increase in extreme events in a warming world. Proceeding of the National Academy of Science, 108 (44) 17905-17909, doi 10.1073/pnas.1101766108.

 (13)Confalonieri, U., B. Menne, R. Akhtar, K.L. Ebi, M. Hauengue, R.S. Kovats, B. Revich and A. Woodward, 2007: Human health. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 391-431.

(14)Easterling, W.E., P.K. Aggarwal, P. Batima, K.M. Brander, L. Erda, S.M. Howden, A. Kirilenko, J. Morton, J.-F. Soussana, J. Schmidhuber and F.N. Tubiello, 2007: Food, fibre and forest products. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 273-313.

(15)Human-induced changes in the hydrology of the western United States
Author(s): Barnett Tim P.; Pierce David W.; Hidalgo Hugo G.; et al.
Source: SCIENCE  Volume: 319   Issue: 5866   Pages: 1080-1083   DOI: 10.1126/science.1152538   Published: FEB 22 2008
Times Cited: 151(from Web of Science)

(16)Climate and wildfire area burned in western U. S. ecoprovinces, 1916-2003
Author(s): Littell Jeremy S.; McKenzie Donald; Peterson David L.; et al.
Source: ECOLOGICAL APPLICATIONS  Volume: 19   Issue: 4   Pages: 1003-1021   DOI: 10.1890/07-1183.1   Published: JUL 2009
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(17)Solomon, S. et al. , 2011, Climate Stabilization Targets, NRC Report. The National Academies Press. Washington, DC, 286 pp.

(18)Distinct causes for two principal US droughtsof the 20th century
Author(s): Hoerling Martin; Quan Xiao-Wei; Eischeid Jon
Source: GEOPHYSICAL RESEARCH LETTERS  Volume: 36     Article Number: L19708   DOI: 10.1029/2009GL039860   Published: OCT 8 2009

(19)Dominant modes of moisture flux anomalies over North America
Author(s): Dominguez F; Kumar P
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(20)Min S., X. Zhang, F. Zwiers, and G. Hegerl, 2011: Human contribution to more-intense precipitation extremes. Nature 2011 Volume: 470, Pages: 378–381. doi:10.1038/nature09763

(21)Anthropogenic greenhouse gas contribution to flood risk in England and Wales in autumn 2000
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Source: NATURE  Volume: 470   Issue: 7334   Pages: 382-385   DOI: 10.1038/nature09762   Published: FEB 17 2011
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