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• August 28, 2013
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Is the Pacific Ocean Responsible for a Pause in Global Warming?

Sea-surface temperatures may explain why climate change is not warming the planet as fast

By David Biello

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From the 1940s through the 1970s there was no major warming trend in the average surface temperature of Earth. At the same time, the tropical Pacific Ocean, which is responsible for the weather patterns known as El Niño and La Niña that can swing global average temperatures by as much as 0.3 degree Celsius, was anomalously cold. For the past decade or so the tropical Pacific has again gone cold—more Niña than Niño—and a new study suggests that the phenomenon may explain the recent “pause” in global warming of average temperatures.

Since 1998’s record heat, average surface temperatures have plateaued for a decade or so—failing to reach new peaks—although the decade also qualifies as the hottest on record. Rising concentrations of greenhouse gases in the atmosphere have not accelerated warming to new heights as rapidly as happened at the end of the 20th century.

To explain this apparent hiatus, climate scientists Shang-Ping Xie and Yu Kosaka of the Scripps Institution of Oceanography at the University of California, San Diego, added the sea. Plugging in observed sea-surface temperatures as well as the more traditional numbers for the extra heat trapped by greenhouse gases into the U.S. Department of Commerce’s Geophysical Fluid Dynamics Laboratory computer model of the oceans and atmosphere might reveal if the cooler tropical Pacific was responsible for the climate change pause. By adding in the sea-surface temperatures of an oceanic area covering roughly 8 percent of the globe, the researchers were able to mimic the recent hiatus in global warming as well as weather phenomena like the prolonged drought in the southern U.S. The results are detailed in Nature on August 29. (Scientific American is part of Nature Publishing Group.) “The tropical Pacific is the engine that drives the global atmosphere and climate,” Xie says. “There were epochs of accelerated and stalled warming in the past,” including that pause in a global warming trend between the 1940s and 1970s, which has often been attributed to sunlight-blocking air pollution from Europe, the Soviet Union and the U.S.

Whereas the largest ocean on a globe that is 70 percent water covered is an obvious driver of climate patterns, it is less clear what drives the cycles of cooling and heating of tropical Pacific Ocean waters. But it is clear that the cool Pacific pattern cannot persist forever to cancel out the extra heat trapped by rising CO2 concentrations, Xie notes.

Other factors—volcanoes, an unusually weak solar cycle, air pollution from China—probably play an important role in restraining global warming as well. Some of the observed climate effects may also stem from other ocean dynamics such as variations in the mixing of surface and deep ocean waters. Already, it appears that ocean waters down to 2,000 meters in depth have trapped a disproportionate share of heat, warming by roughly 0.1 degree C (the equivalent of roughly 36 degrees C of atmospheric warming) since 1955. And the meltdown of significant ice from Greenland or Antarctica might even cool oceans enough to offset the extra heat trapped by rising levels of greenhouse gases for a time. “We need updates to the forcings and a proper exploration of all the different mechanisms together,” says climate modeler Gavin Schmidt of the NASA Goddard Institute for Space Studies. “This has taken time but will happen soon-ish.” The U.N. Intergovernmental Panel on Climate Change will deliver its update on global warming at the end of September.

Despite any pause in the trend toward hotter temperatures, the first decade of the 21st century was the hottest based on records kept since the 1880s—and it included record heat waves in Russia and the U.S. as well as a precipitous meltdown of Arctic sea ice and surging sea level rise. Atmospheric concentrations of CO2 touched 400 parts per million on Mauna Loa in May, a first in the time line of human existence. A cooler Pacific stuck in a La Niña rut may have restrained global warming for the past decade or so, Xie notes, but it is unlikely to last. “This effect of natural variability will be averaged out over a period of 100 years,” he says, “and cannot argue away the threat of persistent anthropogenic warming that is occurring now.”

Who “won” or “lost” tonight’s debate – and opinion was divided – was less important that what new was said by Kevin Rudd.

Most notably, Rudd seemed to significantly toughen the government line on foreign investment in Australian land.

He also appeared open discussion on a more liberal approach on access by people before their retirement to their superannuation.

Foreign investment is a sensitive area – for the economy, relations with other countries and domestic politics.

There have been tensions within the Coalition, where opinion ranges from very “dry” open go Liberals to some Nationals who’d like a much more restrictive policy.

Tonight Rudd was sounding rather like Barnaby Joyce when asked about protecting Australian land from foreign buy ups.

“I’m a bit old-fashioned on these questions and I’m not quite as free market as Tony … maybe it’s because I grew up on a farm,” he said.

He went on to suggest that if undeveloped agricultural land needed a lot more investment, the best way would be a joint venture – approach, comprising equity from farmers, perhaps through co-operatives, with domestic or some external investment.

“I am a bit nervous, a bit anxious, frankly about simply an open slather on this.

“What would our policy approach be? I am looking very carefully at how this affects the overall balance of ownership in Australia. I’m thinking particularly of our agricultural sector, but the impact in certain cities also of these sorts of acquisitions.

“We often get criticised for trying to be protective. I actually look around the world and I see many many countries being equally protective of their own core assets.

“We need to take a more cautious approach to this in the future without throwing the baby out with the bathwater, and I think [with] rural lands and the development of places across northern Australia to boost our agricultural exports we need a better joint venture approach.”

This taps into what has been a very live political issue especially in regional areas. But it did also seemed policy out of nowhere.

At another point he sounded like he was channelling his good friend Bob Katter, as he sympathised with farmers who had told him they were getting squeezed in selling their produce by Coles and Woolworths.

“I’m now worried about that big-time and, therefore, what we’ve got to look at if we are returned … is how we provide better guarantees for proper competitive conduct out there so that the man and woman on the land is not actually having to carry the can for everything.”

Asked about people getting access to some of their superannuation for buying houses to live in (if young) or investment (pre-retirement), Rudd also moved into some new territory. He ruled this out for the young but said “for older folk, we need to look at how people can gain access to funds earlier, which is their money.”

By his comments on foreign investment especially Rudd has opened new fronts of policy debate for the latter stage of this campaign. It’s unclear whether this was his intention.

His remarks will be scrutinised in China and domestically he will be pressed for more detail. Obvious questions arise – such as, did he consult colleagues about hardening the government’s position?

It does seem strange to announce this in the debate forum. It was not like his deliberate strategy in the initial debate of dropping his plan for a gay marriage bill in the first hundred days. This appeared more a case that the question happened to tap into what was in his head.

The audience of undecided voters scored the debate 45 to 38 to Rudd. This encounter lacked the liveliness of the Brisbane forum; there were a few barbs but no “does this guy ever shut up?” moment. Rudd made a point of saying he would stay to talk to people (because that worked for Abbott last time). No doubt he was very nice to the make-up woman.

Rudd seemed more animated than Abbott. He kept his cool during some critical questions, notably one about his destabilising Julia Gillard’s leadership. When challenged on his proposal to relocate ships from Garden Island he declared “I don’t apologise for being in the vision business.”

He repeatedly hammered Abbott about his paid parental leave scheme, and pushed the opposition leader on why he would not release his policy costings and budget bottom line then and there.

Both leaders pledged to keep all their promises – an undertaking that the winner will inevitably break.

Abbott batted through in a night-watchman sort of style. He didn’t radiate any sense of excitement and had a lot of same-old, same-old lines (ending carbon tax, stopping boats etc), although he did say the Coalition was not planning to shut any Medicare Locals, a guarantee he declined to give a few days ago.

But they won’t be raising eyebrows in Beijing or anywhere else about what he said and he didn’t open up any big new questions for the morning. And he’d rate that as a very satisfactory outcome.

Australian Greens

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