Between 1998 and 2012, climate scientists observed a slowdown in the rate at which the Earth's surface air temperature was rising. While the rise in global mean surface air temperature has continued, between 1998 and 2012 the increase was approximately one third of that from 1951 to 2012.


This trend — referred to as a "global warming hiatus" — has sparked a lot of debate and given rise to a reasonable question: Is global warming coming to a halt?


According to Norman Loeb, an atmospheric scientist at NASA's Langley Research Center in Hampton, Virginia, and the principal investigator of a space-borne sensor called the Clouds and Earth's Radiant Energy System, or CERES, the answer is almost certainly no.


"Heating is still going on," he said. "It's just not in terms of the surface air temperature."


Loeb explained the science behind that statement Tuesday, Aug. 5, during a talk at NASA Langley titled "The Recent Pause in Global Warming: A Temporary Blip or Something More Permanent?"


Though Loeb believes there are a handful of short-term factors that drive changes in surface air temperature, like the El Niño and La Niña phenomena that cause temperature fluctuations in the tropical eastern Pacific approximately every two years, he thinks there is a longer term factor that is a significant and overlooked contributor.


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In other words, as humans and nature continue to apply pressure to the Earth's climate through increases in carbon dioxide and other greenhouse gases, temperatures are still rising. But as the Pacific Decadal Oscillation briefly tames temperatures at the planet's surface, the oceans are where the real heating is happening.


"If you add extra heat to the Earth system, approximately 93 percent of that extra heat ends up stored in the ocean, and the ocean is very deep," Loeb said. "When we look at air temperature, we are just looking at the surface. There's a whole deep ocean where heat can be stored."


http://climate.nasa.gov/news/1141/

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