Climate change skeptics are playing up recent indications of a slowdown in global warming but heat may be stored below the surface of oceans, a U.S. study said. Scientists reconstructing Pacific Ocean temperatures for the last 10,000 years found its middle depths have warmed 15 times faster in the last 60 years than they did during apparent natural warming cycles in the previous 10,000 years, the Earth Institute at Columbia University reported Thursday. Although many scientists agree much of the heat humans have put into the atmosphere since the 1970s through greenhouse gas emissions probably has been absorbed by the ocean, the new study suggests the oceans may be storing even more of the effects of human emissions than scientists have so far realized, a Columbia release said. "We're experimenting by putting all this heat in the ocean without quite knowing how it's going to come back out and affect climate," said study coauthor Braddock Linsley, a climate scientist at Columbia's Lamont-Doherty Earth Observatory. "It's not so much the magnitude of the change, but the rate of change." The study refutes claims by climate change skeptics that industrial carbon emissions are not causing a century-long rise in Earth's surface temperatures, the researchers said. "We may have underestimated the efficiency of the oceans as a storehouse for heat and energy," study lead author Yair Rosenthal, a climate scientist at Rutgers University, said. "It may buy us some time -- how much time, I don't really know. But it's not going to stop climate change."