1D Mannequin of World SST Reveals 40% of Warming Since 1979 Resulting from Early Volcanic Cooling

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From Dr. Roy Spencer’s Weblog

January 14th, 2020 by Roy W. Spencer, Ph. D.

In 2017, Christy & McNider revealed a research the place they estimated and eliminated the volcanic results from our UAH decrease tropospheric (LT) temperature report, discovering that 38% of the post-1979 warming pattern was attributable to volcanic cooling early within the report.

Yesterday in my weblog submit I confirmed outcomes from a 1D 2-layer forcing-feedback ocean mannequin of global-average SSTs and deep-ocean temperature variations up via 2019. The mannequin is compelled with (1) the RCP6 radiative forcings situation (principally growing anthropogenic greenhouse gases and aerosols and volcanoes) and (2) the noticed historical past of El Nino and La Nina exercise as expressed within the Multivariate ENSO Index (MEI) dataset. The mannequin was optimized with adjustable parameters, with two of the necessities being mannequin settlement with the HadSST international temperature pattern throughout 1979-2019, and with deep-ocean (Zero-2000m) warming since 1990.

Because the interval since 1979 is of such curiosity, I re-ran the mannequin with the RCP6 volcanic aerosol forcing estimates eliminated. The outcomes are proven in Fig. 1.


Fig. 1. 1D mannequin simulation of worldwide (60N-60S) common sea floor temperature departures from assumed vitality equilibrium (in 1765), with and with out the RCP6 volcanic radiative forcings included.

The outcomes present that 41% of the ocean warming within the mannequin was merely because of the two main volcanoes early within the report. That is in good settlement with the 38% estimate from the Christy & McNider research.

It’s attention-grabbing to see the “true” warming results of the 1982-83 and 1991-1993 El Nino episodes, which had been masked by the eruptions. The height mannequin temperatures in these occasions had been solely Zero.1 C beneath the record-setting 1997-98 El Nino, and Zero.2 C beneath the 2015-16 El Nino.

This isn’t a brand new situation, in fact, as Christy & McNider additionally revealed an analogous evaluation in Nature in 1994.

These volcanic results on the post-1979 warming pattern ought to at all times be stored in thoughts when discussing the post-1979 temperature developments.

NOTE: In a earlier model of this submit I advised that the Christy & McNider (1994) paper had been scrubbed from Google. It seems that Google couldn’t discover it if the authors’ center initials had been included (however DuckDuckGo had no drawback discovering it).

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