At Watts Up With That?, Bob Tisdale explains how the oceans temper any global warming that might otherwise be occurring. It is hard to comprehend the vast capacity of the oceans, which average 4,000 meters deep, to absorb heat:
It is often said that more than 90% of the heat caused by manmade greenhouse gases is absorbed by the oceans. But as skeptics often note, the absorbed heat has little impact on the temperatures of the oceans to depth, and that’s because of the seemingly limitless capacity of the oceans to store heat.
In the early 2000s, floats were placed around the world at depths of up to 2,000 meters to read temperatures. NOAA has compiled these data for the years 2005 to the present, showing the vertically average temperature anomaly and calculating, from that, the amount of heat being absorbed. This is the key point:
A hypothetical energy imbalance resulting from the emissions of manmade greenhouse gases has caused the oceans to absorb heat from 2005 to 2013 at a rate of about 8.6*10^22 Joules/decade, according to the NODC data for the depths of 0 to 2000 meters, but due to the heat capacity of the oceans, the oceans for those same depths have only warmed at a rate of about 0.03 deg C/decade, also according to NODC data.
Moreover, that tiny number overstates the actual warming of the oceans, since they are far deeper than 2,000 meters: 0.015 degrees C per decade would be closer. This number is essentially zero; there is no conceivable way anyone could measure the average temperature of the oceans over the entire Earth, from surface to ocean floor, with that degree of accuracy. Further, the time frame is ridiculously short. Nevertheless, if you assume the NOAA data are valid from 2005 to the present and project the same rate of warming into the future, the oceans will have warmed by one degree in a mere 670 years.
As usual, the WUWT comments are well worth reading. They convey a sense of how vigorously the debate over climate is raging, and how far we are from anything like a complete understanding.