A new study estimates that about half the global warming that has taken place since the 1970s can be attributed to natural climate cycles that heat up and cool the planet over time.
Dr. Roy Spencer of the University of Alabama, Huntsville found that by including historical observations of El Niño ocean warming events and La Nina cooling events, a portion of warming since the 1950s can be attributed to El Niño.
Furthermore, because the globe is experiencing more La Niñas in recent decades, warming from stronger El Niño is being is being canceled out.
“As a result, because as much as 50% of the warming since the 1970s could be attributed to stronger El Niño activity, it suggests that the climate system is only about half as sensitive to increasing CO2 as previously believed,” Spencer said.
Spencer’s study, to be published in the in the Asia-Pacific Journal of Atmospheric Science, finds that climate sensitivity — the amount of warming from a doubling of carbon dioxide concentrations — is about half of what most climate scientists expect.
“Basically, previously it was believed that if we doubled the CO2 in the atmosphere, sea surface temperatures would warm about 2.5 C,” Spencer added. “But when we factor in the ENSO warming, we see only a 1.3 C final total warming after the climate system has adjusted to having twice as much CO2.”
It has been known for some time that Pacific Ocean natural warming and cooling cycles come and go in the 30-year cycles. La Nina cooling events were dominant during the 1950s to the 1970s, while El Niño warming events dominated the late 1970s to the late 1990s. The study suggests that the globe could currently be in a cooling period — which would explain the lack of warming since 1998.
If this is true, Spencer said people can expect to see slight warming period once El Niño become dominant again.
The study’s release coincides with the opening of climate talks in Warsaw, Poland where international delegates hope to clear the way for an international agreement for global warming in 2015.
The conference has so far been overshadowed by the massive typhoon that has killed thousands in the Philippines and being pointed to by activists as evidence that the world needs to act now to combat global warming.
“We can fix this. We can stop this madness. Right now, right here,” Naderev Sano, delegate from the Philippines, told delegates as he broke down into tears.
However, the United Nation’s most recent climate report said that there is little evidence that manmade global warming is altering tropical cyclone activity. Yet researchers do say that storms could become more potent in years to come as the planet warms.
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