Study shows summer climate change, mostly warming

Nov 13, 2012

Analysis of 90 years of observational data has revealed that summer climates in regions across the globe are changing—mostly, but not always, warming —according to a new study led by a scientist from the Cooperative Institute for Research in Environmental Sciences headquartered at the University of Colorado Boulder.

"It is the first time that we show on a local scale that there are significant changes in summer temperatures," said lead author CIRES scientist Irina Mahlstein. "This result shows us that we are experiencing a new summer climate regime in some regions."

The technique, which reveals location-by-location temperature changes rather than global averages, could yield valuable insights into changes in ecosystems on a regional scale. Because the methodology relies on detecting temperatures outside the expected norm, it is more relevant to understand changes to the animal and plant life of a particular region, which scientists would expect to show sensitivity to changes that lie outside of normal variability.

"If the summers are actually significantly different from the way that they used to be, it could affect ecosystems," said Mahlstein, who works in the Chemical Sciences Division of the 's Research Laboratory.

To identify potential temperature changes, the team used recorded from 1920 to 2010 from around the globe. The scientists termed the 30-year interval from 1920 to 1949 the "base period," and then compared the base period to other 30-year test intervals starting every 10 years since 1930.

The comparison used statistics to assess whether the test interval differed from the base period beyond what would be expected due to yearly for that .

Their analysis found that some changes began to appear as early as the 1960s, and the observed changes were more prevalent in . In these regions, temperatures varied little throughout the years, so the scientists could more easily detect any changes that did occur, Mahlstein said.

The scientists found significant summer in 40 percent of tropical areas and 20 percent of higher-latitude areas. In the majority of cases, the researchers observed warming summer temperatures, but in some cases they observed cooling .

"This study has applied a new approach to the question, 'Has the temperature changed in local areas?' " Mahlstein said. The study is in press in the journal Geophysical Research Letters, a publication of the American Geophysical Union.

The study's findings are consistent with other approaches used to answer the same question, such as modeling and analysis of trends, Mahlstein said. But this technique uses only observed data to come to the same result. "Looking at the graphs of our results, you can visibly see how things are changing," she said.

In particular the scientists were able to look at the earlier time periods, note the temperature extremes, and observe that those values became more frequent in the later time periods. "You see how the extreme events of the past have become a normal event," Mahlstein said.

The scientists used 90 years of data for their study, a little more than the average lifespan of a human being. So if inhabitants of those areas believe that summers have changed since they were younger, they can be confident it is not a figment of their imagination.

"We can actually say that these changes have happened in the lifetime of a person," Mahlstein said.

Explore further: Canada to push Arctic claim in Europe

add to favorites email to friend print save as pdf

Related Stories

Research links extreme summer heat events to global warming

Aug 06, 2012

(Phys.org) -- A new statistical analysis by NASA scientists has found that Earth's land areas have become much more likely to experience an extreme summer heat wave than they were in the middle of the 20th century. The research ...

Extreme summer temperatures occur more frequently: study

Feb 15, 2012

(PhysOrg.com) -- 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 ...

Climate vs. weather: Extreme events narrow the doubts

Aug 22, 2012

Heatwaves, drought and floods that have struck the northern hemisphere for the third summer running are narrowing doubts that man-made warming is disrupting Earth's climate system, say some scientists.

Recommended for you

Canada to push Arctic claim in Europe

40 minutes ago

Canada's top diplomat will discuss the Arctic with his Scandinavian counterparts in Denmark and Norway next week, it was announced Thursday, a trip that will raise suspicions in Russia.

Severe drought is causing the western US to rise

6 hours ago

The severe drought gripping the western United States in recent years is changing the landscape well beyond localized effects of water restrictions and browning lawns. Scientists at Scripps Institution of ...

A NASA satellite double-take at Hurricane Lowell

6 hours ago

Lowell is now a large hurricane in the Eastern Pacific and NASA's Aqua and Terra satellites double-teamed it to provide infrared and radar data to scientists. Lowell strengthened into a hurricane during the ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

ArtflDgr
2.1 / 5 (7) Nov 13, 2012
0.009% of the time man has had civilization, and all up at one end of it
Tangent2
4.2 / 5 (5) Nov 13, 2012
Complaining that we don't have a full data set since the dawn of man isn't going to help any here, unless you have a solution. The measurements have to start somewhere and at sometime. And besides, even with such a small window of data they were STILL able to discern a changing trend. That should be the highlight.
Howhot
3.7 / 5 (3) Nov 15, 2012
The scientists found significant summer temperature changes in 40 percent of tropical areas and 20 percent of higher-latitude areas. In the majority of cases, the researchers observed warming summer temperatures,...


That about sums it up... Now just wait 10 years more and you will see another 1 degree C increase in Global average temperatures. AGW is just that predictable.