Summers Are Getting Warmer
November 13, 2012

Study Shows Summer Climate Is Warming Up

Lee Rannals for — Your Universe Online

According to a new study published in the journal Geophysical Research Letters, summer climates in regions across the globe are mostly warming.

Scientists from the Cooperative Institute for Research in Environmental Sciences headquartered at the University of Colorado Boulder performed an analysis of 90 years of observational data to reveal how the summers are changing.

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

The technique could provide valuable insights into changes in ecosystems on a regional scale, according to the study. Its methodology relies on detecting temperatures outside the normal range, making it more relevant to understand changes to the animal and plant life of a certain region.

"If the summers are actually significantly different from the way that they used to be, it could affect ecosystems," Mahlstein said in the statement.

The team used climate observations recorded from 1920 to 2010 and from around the world in order to identify potential temperature changes.

They 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 researchers used statistics to assess whether the test interval was different from the base period beyond what would be expected due to yearly temperature variability for that region. They found some changes began to appear as early as the 1960s and the observed changes were more known through the tropical areas.

In these regions, Mahlstein said temperatures varied little throughout the years, so the scientists could more easily detect any changes that did occur.

The scientists found summer temperature changes in 40 percent of tropical areas and 20 percent of higher latitude areas. They also observed warming summer temperatures, but in some cases saw cooling summer temperatures.

"This study has applied a new approach to the question, 'Has the temperature changed in local areas?' " Mahlstein said.

The findings are consistent with other techniques used to answer the same question, according to Mahlstein. However, she said this technique only used 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.

The team looked at the earlier time periods, noted the temperature extremes and observed 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 in the statement.

The study authors used 90 years of data during their research, which is a little more than the average lifespan of a human. If inhabitants of those areas believe 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.