The air has not warmed for 15 years. Now scientists create a solution to the puzzle: the Pacific cools the world
Hamburg - The rising temperature curve is a symbol of the man-made climate change. Each UN climate report, the effective slide forward. Due to recent climate changes , however, she has lost weight : The climate has not warmed for 15 years , the curve no longer shows up - although mankind is increasingly blowing carbon dioxide into the atmosphere.
According to forecasts, it should have been warmer by about 0.25 degrees since the turn of the millennium . Computer models could not explain the development so far . Only two percent of the simulations showed such a long lasting temperature dip , German researchers report in a new study . Now scientists believe they have found the explanation. Cool Pacific water is responsible for the shutdown of the heating of the air , researchers report in the scientific journal "Nature".
What sound to outsiders may seem like a sleight - trick based on sound physics. Most of the energy enters the oceans , they swallow about 90 percent of the heat . In their top three meters of the ocean hold as much heat as the entire flight envelope of the earth. Rhythmic fluctuations of ocean currents change the weather for years to come . An unusually warm tropical Pacific as a so-called El Niño , ensures every few years for severe weather .
Drought, heat, wind
Recently , the opposite phenomenon was heaped : Multiple La Niña was reared in the Pacific cold deep water had risen to the surface, it pushes warm water down - and cools the air. Although the tropical eastern Pacific only covered one twelfth of the earth , explain its cooling almost completely why the air was not heated in the global average in recent years , Yo Kosaka and Shang -Ping Xie report from the University of California at San Diego "Nature".
They had succeeded with a computer model that accurately simulate the climate. Faithfully show the simulation of the regional weather of recent years such as the 2012 drought in the U.S., hotter summers in northern latitudes or air currents over the Pacific. Above all, a connection sting out : Simultaneous with the temperature of the eastern Pacific vacillate since 1970 the global temperature . Is the mystery of the heating pause so resolved?
"The work shows that a cooling of the tropical Pacific may constitute a decelerated global warming," says Stefan Brönnimann, climatologist at the University of Bern . It is remarkable that the Pacific cooling in the model the global climate fluctuations nachbilde as well , adds Doug Smith of the UK Met Office . Presumably, the natural variation in the Pacific could adequately explain the warming pause , agrees Gerald Meehl of the National Center for Atmospheric Research in the United States . His previous simulations had already suggested the relationship .
open questions
About the cause of climate variability , however, the new study has not indicated emphasizes Brönnimann : Why the Pacific has cooled ? This question remains open . The cooling of the Pacific could have been caused by other climatic influences - which thus would ultimately be the cause of the heating pause , agrees Smith.
"The study does not explain the unusual temperature profile ," says Kevin Trenberth of the National Center for Atmospheric Research in the U.S. ( NOAA) . Because it lacked a declaration where the heat would have shifted . A team led by Trenberth was recently able to show that the deep sea could have swallowed a third of global warming.
Could probably also changes the radiation budget of the Earth partly explain the unexpected temperature profile , says the researcher . Examples are dried up in recent years, high air layers . Your water vapor acts as a thermal buffer. The dryness of the stratosphere have therefore contributed to the warming pause , researchers report. Furthermore, increases in emissions in Asia or volcanic eruptions have dimmed the sunlight. The weakness of the sun seems to have slowed down slightly to climate change .
" The uncertainty is high ," says Andrey Kostianoy of the Russian Academy of Sciences in Moscow . Open question , whether other oceans vorgäben climate rhythm. " The Southern Ocean has been especially cooled during the past decades , he has contributed to the respite of global warming ," adds the climatologist Mojib Latif of the Helmholtz Centre for Ocean Research Kiel . Latif had predicted in 2008 that oceans would temporarily slow down climate change .
The prediction was an isolated case. Only now the place science at the heart of the seas . The British Met Office believes now that the rest of the global warming will continue for a few years. However, the buffer temperature of the oceans was only temporary , says Brönnimann . The greenhouse gases would exert their warming effect , stated the UN climate report, to be published shortly. Maybe even follow a phase of accelerated warming.
