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.
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