Featured Research

from universities, journals, and other organizations

Extreme summer temperatures occur more frequently in U.S. now, analysis shows

Date:
February 15, 2012
Source:
DOE/Lawrence Livermore National Laboratory
Summary:
Extreme summer temperatures are already occurring more frequently in the United States, and will become normal by mid-century if the world continues on a business as usual schedule of emitting greenhouse gases. By analyzing observations and results obtained from climate models, a new study has shown that previously rare high summertime (June, July and August) temperatures are already occurring more frequently in some regions of the 48 contiguous United States.

The white colored rock (approximately 100 feet high) shows the drop in the water level of Lake Mead as a result of the ongoing 10-year drought along the Colorado River.
Credit: Guy DeMeo , U.S. Geological Survey

Extreme summer temperatures are already occurring more frequently in the United States, and will become normal by mid-century if the world continues on a business as usual schedule of emitting greenhouse gases.

Related Articles


By analyzing observations and results obtained from climate models, a study led by Phil Duffy of the Lawrence Livermore National Laboratory showed that previously rare high summertime (June, July and August) temperatures are already occurring more frequently in some regions of the 48 contiguous United States.

"The observed increase in the frequency of previously rare summertime-average temperatures is more consistent with the consequences of increasing greenhouse gas concentrations than with the effects of natural climate variability," said Duffy, who is the lead author of a report in a recent edition of the journal, Climatic Change. "It is extremely unlikely that the observed increase has happened through chance alone."

The geographical patterns of increases in extreme summer temperatures that appear in observations are consistent with those that are seen in climate model simulations of the 20th century, Duffy said.

Duffy and colleague Claudia Tebaldi, a senior scientist at the nonprofit news and research group Climate Central, showed that the models project that previously rare summer temperatures will occur in well more than 50 percent of summers by mid-century throughout the lower 48 states.

The team first compared the period 1975-2000 to the preceding 25 years, and found that both observations and results based on 16 global climate models show that summertime-average temperatures that were rare in the earlier period occurred more often in the later period, in certain regions. The agreement between observations and models demonstrates that the models are able to simulate changes in the occurrence of extreme summertime temperatures, Duffy said.

Duffy and Tebaldi performed a statistical analysis showing that the increases in rare summer temperatures seen in the later period are very unlikely to have occurred through chance weather variations.

Next, Duffy and Tebaldi assessed the present period, by using results obtained from climate models for 1995-2024; they found that summer temperatures that were extreme during 1950-1979 occur more often in the later time period. This supports the conclusion that extreme summertime temperatures are already occurring more frequently in parts of the lower 48 states. A second statistical analysis showed that this increase also is very unlikely to be due to chance weather variations alone, such as El Ninos or La Ninas.

Finally, the team evaluated model results for 2035-2064 (representing the middle of this century) and found that extreme summertime temperatures that were rare during 1950-1979 are projected to occur in most summers throughout the 48-state region in the mid-century period. For the mid-century, summertime mean temperatures that historically occurred only 5 percent of the time are projected to occur at least 70 percent to the time everywhere in the 48 state region.

"The South, Southwest and Northeast are projected to experience the largest increases in the frequency of unusually hot summers," Duffy said. "The strong increase in extremes in the Southwest and Northeast are explained by strong historical and projected warming there. This result is based upon assuming a commonly used scenario for future emissions of carbon dioxide, the main driver of human-caused climate change.

"What was historically a one in 20-year occurrence will occur with at least a 70 percent chance every year. This work shows an example of how climate change can affect weather extremes, as well as averages."


Story Source:

The above story is based on materials provided by DOE/Lawrence Livermore National Laboratory. Note: Materials may be edited for content and length.


Journal Reference:

  1. P. B. Duffy, C. Tebaldi. Increasing prevalence of extreme summer temperatures in the U.S.. Climatic Change, 2012; 111 (2): 487 DOI: 10.1007/s10584-012-0396-6

Cite This Page:

DOE/Lawrence Livermore National Laboratory. "Extreme summer temperatures occur more frequently in U.S. now, analysis shows." ScienceDaily. ScienceDaily, 15 February 2012. <www.sciencedaily.com/releases/2012/02/120215143116.htm>.
DOE/Lawrence Livermore National Laboratory. (2012, February 15). Extreme summer temperatures occur more frequently in U.S. now, analysis shows. ScienceDaily. Retrieved March 1, 2015 from www.sciencedaily.com/releases/2012/02/120215143116.htm
DOE/Lawrence Livermore National Laboratory. "Extreme summer temperatures occur more frequently in U.S. now, analysis shows." ScienceDaily. www.sciencedaily.com/releases/2012/02/120215143116.htm (accessed March 1, 2015).

Share This


More From ScienceDaily



More Earth & Climate News

Sunday, March 1, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Whale-Watching Scientists Spot Baby Orca

Whale-Watching Scientists Spot Baby Orca

AP (Feb. 28, 2015) Researchers following endangered killer whales spotted a baby orca off the coast of Washington state, the third birth documented this winter but still leaving the population dangerously low. (Feb. 28) Video provided by AP
Powered by NewsLook.com
Bridge Collapses Due to Flooding in Bolivia

Bridge Collapses Due to Flooding in Bolivia

Reuters - News Video Online (Feb. 28, 2015) Heavy rain and flooding sweep through parts of Bolivia causing damage and leaves more than 2,000 people homeless. Sophia Soo reports. Video provided by Reuters
Powered by NewsLook.com
Death Toll from Afghan Avalanches Tops 200

Death Toll from Afghan Avalanches Tops 200

AFP (Feb. 27, 2015) More than 200 people have been killed in a series of avalanches triggered by heavy snowfall in Afghanistan. Duration: 00:42 Video provided by AFP
Powered by NewsLook.com
France, Philippines Call for Agreement on Climate Change

France, Philippines Call for Agreement on Climate Change

Reuters - News Video Online (Feb. 27, 2015) The presidents of France and the Philippines issue a joint appeal for a binding agreement on climate change. Katie Sargent reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins