One of the ways in which climate scientists evaluate the role of anthropogenic greenhouse emissions in the recent warming of Earth’s climate is to run climate models both with and without human activities. By comparing the results of each to the observed temperature trend, these “fingerprinting” studies can show how much of the temperature record can be explained by natural factors (such as solar activity and volcanic eruptions). This has commonly been applied to trends in atmospheric temperatures (as shown in the 2007 IPCC report), where it’s clear that the observed warming wouldn’t have happened without rising greenhouse gases.
Increasingly reliable records of ocean temperatures have now allowed some of these same researchers to confidently apply the technique to Earth’s seas. This is important because some 90 percent of all the energy trapped by human greenhouse emissions has ended up in the ocean, not the atmosphere. The trend with ocean heat content is clear—it’s rising. The question is whether that rise could be caused by natural variations.
Researchers averaged the results from a number of climate models, and compared that to global temperature records for the upper 700 meters of the ocean from 1960 to 1999. The temperature record is less complete for the deep ocean, and its massive volume and separation from the surface subdues its response to climatic changes. In addition to the global average, they also analyzed each of the major ocean basins (North and South Atlantic, North and South Pacific, North and South Indian) separately.
from Ars Technica http://arstechnica.com
