Snow in London last winter prompted mayor Boris Johnson to proclaim there mustn’t be such a thing as global warming. A recent spate of cooler temperatures in the Pacific Ocean starting around 1998 could alike be seen as a climate change denier’s dream come true. A new study suggests that this slowdown in global average surface temperatures is a temporary and brief phenomenon.
Researchers from the Scripps Institution of Oceanography in La Jolla, California used computer modeling to study the “global warming hiatus,” which has occurred at the same time as the United States has experienced record-breaking heat, Arctic sea ice has continued to shrink and Greenland has become greener as its ice shelf has melted.
The Pacific decadal oscillation is the name for a La Niña-like cooling trend in the eastern equatorial Pacific. La Niña and El Niño are known to alternately warm and cool the sea surface of the tropical Pacific. Their effects are felt around the world in the form of monsoons and temperature changes.
While as little as 8 percent of the earth’s surface is affected by this cooling trend, it is still enough to “offset the general rise in temperature induced by anthropogenic greenhouse gases,” says scientist Shang-Ping Xie. While the La Niña conditions suppressed global average temperatures during the winter in the Northern Hemisphere, summer temperatures in the region still rose.
If the Scripps researchers are accurate, then “it seems very likely that the energy being trapped by greenhouse gases is indeed going into the deep ocean,” says Andrew Dessler, a climatologist at Texas A&M University in College Station.
Research indicates that oceans have absorbed much of the heat and about a third of the additional carbon dioxide pumped into the air from pre-industrial times. This has an effect – the thermal expansion of the oceans is likely to be the biggest factor behind sea level rise, and the absorption of carbon dioxide is making the oceans more acidic.
The cooling phase could mean that global temperatures may not be riding at the highest estimate of 6 degrees Celsius. But a lower predicted rise of 2 degrees Celsius from greenhouse gas emissions can still, as we have seen, cause extreme weather events.
The last cooling phase before the most recent one occurred in the 1940s to the 1970s. Xie is not sure how long the cooling trend will last and comments that it is simply a matter of time before “the Pacific Ocean decides to swing into a warmer state.” Climate change deniers can say what they want but (for the nth) time, global warming is all too real.
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