Wednesday, August 28, 2013
If you look at weather records stretching back over the last century, the trend is clear. As humans pump more and more greenhouse gasses into the atmosphere, temperatures rise, but if you narrow your view to the last 15 years, you'll see something weird: Carbon dioxide emissions keep going up, but temperatures stay more or less flat.
In recent years, global temperatures have not spiked as much as expected, but that doesn't mean climate change isn't happening. In order to account for this warming hiatus, San Diego researchers trained their sights on cooling in the Pacific Ocean.
Climate change deniers have pounced on that fact, saying it exposes global warming as a hoax. However, a new study led by Shang-Ping Xie at the Scripps Institution of Oceanography says that's not the case at all.
The researchers focused on the ocean surface in the tropical Pacific. Their new climate model shows that this important storm-generating region has been going through the cooling phase of an ongoing cycle, which in turn has halted warming around the Earth.
Temperatures may be stable now but Xie warned, "The natural cycle of the Pacific Ocean is eventually going to swing up. And when that happens, we are going to see very strong, fast warming ... return."
In fact, this isn't the first time climate scientists have observed a warming hiatus. Global mean temperatures stayed relatively constant from the 1940s through the '70s, as well. Xie notes that the previous tropical Pacific cooling epoch occurred at the same timeframe.
Xie says however you approach climate change, looking at just the last 15 years will never give you a clear picture of what's happening to the planet.
"You hear two stories," he explained. "One the one hand, people show you a 130-year record concluding carbon dioxide is causing the temperature rise, and then somebody else shows you a 15-year record saying carbon dioxide has nothing to do with it. So which one do you want to believe? "