Deep oceans of the world sometimes can absorb enough heat to flatten the pace of global warming in periods as long as a decade, even longer-term warming, according to a new analysis conducted by the National Center for Atmospheric Research (NCAR).
The study is based on computer simulations of global climate, highlighting the deep ocean layers 1,000 feet (300 meters) as the main location of "lack of heat" periods, as the last decade, when the temperature of the air world showed little trend. The results also suggest that several large bands, as can be expected during the next century, although the trend of global warming.
"We will see global warming goes through periods of hiatus in the future," said Gerald Meehl NCAR and lead author of the study. "However, these periods would probably last only a decade, and heating will resume . This study illustrates one of the reasons why the global temperature rise is not only a straight line. "
Research by scientists at NCAR and the Bureau of Meteorology of Australia, will be published online Sept. 18 in the nature of climate change. Funding for this study came from the National Science Foundation, NCAR's sponsor and the Department of Energy.
If the heat disappears
2000 was the warmest decade of the Earth over a century of weather records. But a single warmest year in global temperatures, which were closed in 1998, remained unsurpassed until 2010.
However, emissions of greenhouse gases continue to rise in 2000, and satellite measurements have shown that the discrepancy between the sunlight and outgoing radiation from Earth, in augmented reality. This meant that the heat was building somewhere on Earth, the 2010 study published in the NCAR scientists, researchers, Kevin Trenberth, John Fake.
The two scientists, who are co-authors of the new study suggests that the oceans could be storing some of the heat that would otherwise go to other processes, such as global warming or the floor or the melting of ice and snow more . Observations from a worldwide network of buoys showed a warming in the ocean surface, but not enough to account for heat build global economy. Although scientists suspect that the deep ocean have a role to play, little has been available to confirm this hypothesis.
To know where the heat is gone, Meehl and his colleagues used a powerful software tool known as the model of the EU system of climate change, which was developed by scientists at NCAR and the Department of Energy with colleagues other organizations. Using the model's ability to represent the complex interactions between atmosphere, land, oceans and sea ice, which made five simulations of global temperatures.
The simulations are based on projections of future emissions of greenhouse gases from human activities, said that the temperature rises a few degrees during this century. But each simulation also showed periods where temperatures will stabilize for about a decade before climbing again. For example, a simulation of global mean temperature increases by about 2.5 degrees Fahrenheit (1.4 degrees Celsius) between 2000 and 2100, but the two rest periods of a decade during this century.
In these periods of hiatus, the simulations showed that the extra energy in the oceans, with the deeper layers to absorb a disproportionate amount of heat due to changes in ocean circulation. The great sea surface below 1000 feet (300 meters) heated with 18% to 19% more during periods of rest at other times. However, global warming the upper ocean over 1,000 yards with 60% less than non-break periods in the simulation.
"This study suggests a lack of energy was really thrown into the sea," says Trenberth. "The heat has not gone away, so it can not be ignored. There must be consequences."
A model such as La Niña
The simulations also indicate that the world's oceans during periods of rest is a regional firm. During a break, the average sea surface temperatures in the tropical Pacific decreases, while tending to increase at higher latitudes, especially around 30 ° S and 30 ° N and 35 N Pacific and 40 ° N in the Atlantic, where surface waters converge to push the heat in the deep ocean.
These trends are similar to those observed during La Niña, according to Meehl. He added that El Niño and La Niña are superimposed on a pattern of related pause. Global temperatures tend to decrease slightly during La Niña, cold waters that reach the surface of the tropical Pacific and a slight increase during El Niño, when the waters are warmer.
"The main difference in the observed warming has corresponded with La Niña, which is consistent with simulations," says Trenberth.
The simulations were part of NCAR's contribution to the phase of the Coupled Model Intercomparison Project 5 (CMIP5). They were executed on NCAR supercomputers the National Science Foundation sponsored by the Climate Simulation Laboratory, and on supercomputers at Oak Ridge Leadership Computing Facility and Energy National Centre for Scientific Computing Research, supported by the Office Science US Department of Energy.
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