Where’s the heat? Warming of Pacific Ocean fastest seen in 10,000 years

Skeptics have made much of the so called 15 year “pause” in warming for land surface temperatures, while conveniently overlooking the warming oceans.

A study just released this week in Science indicates the Pacific Ocean may be warming at a rate faster than it has in the last 10,0000 years [pay wall]:

Observed increases in ocean heat content (OHC) and temperature are robust indicators of global warming during the past several decades. We used high-resolution proxy records from sediment cores to extend these observations in the Pacific 10,000 years beyond the instrumental record. We show that water masses linked to North Pacific and Antarctic intermediate waters were warmer by 2.1 ± 0.4°C and 1.5 ± 0.4°C, respectively, during the middle Holocene Thermal Maximum than over the past century. Both water masses were ~0.9°C warmer during the Medieval Warm period than during the Little Ice Age and ~0.65° warmer than in recent decades. Although documented changes in global surface temperatures during the Holocene and Common era are relatively small, the concomitant changes in OHC are large.

This study was also reported in the LA Times, where some (genuine) climate scientists expressed scepticism about the rate of warming. Still it is very clear the oceans have been acting as a “buffer” in absorbing additional heat. However we can’t bank on the oceans performing this role in future centuries:

“This is much faster than anything we’ve seen in the long term,” said Yair Rosenthal, a professor of earth sciences at Rutgers University and lead author of the study.

The timing could be fortuitous, because we may be pumping the atmosphere full of carbon after a naturally-occurring cooldown, just when the oceans are most prepared to absorb the heat, Rosenthal said.

“There may be some hope, “ he said, “because maybe the ocean will be able to store more heat than we were estimating before.”

It could also spell trouble. While temperatures in the atmosphere go up and down pretty quickly, seawater can absorb a lot of heat before its temperature rises. So even if carbon emissions are reduced, it could take years or even centuries for the ocean to respond, a lag that could have consequences far into the future.

[Image source: Scientific American]