New 80-12 months Deep-Ocean Temperature Dataset In comparison with a 1D Local weather Mannequin

Reposted from Dr. Roy Spencer’s website

January 15th, 2020 by Roy W. Spencer, Ph. D.

The growing international ocean warmth content material (OHC) is commonly pointed to as probably the most quantitative approach to monitor long-term modifications within the international vitality steadiness, which is believed to have been altered by anthropogenic greenhouse fuel emissions. The problem is that long-term temperature modifications within the ocean under the highest hundred meters or so develop into exceedingly small and troublesome to measure. The newer community of Argo floats for the reason that early 2000s has improved international protection dramatically.

A brand new Cheng et al. (2020) paper describing document heat ocean temperatures in 2019 has been mentioned by Willis Eschenbach who appropriately reminds us that such “document setting” modifications within the Zero-2000 m ocean warmth content material (reported in Zettajoules, which is 10^^21 Joules) quantity to exceedingly small temperature modifications. I calculate from their knowledge that 2019 was solely Zero.004 Zero.009 deg. C hotter than 2018.

Over time I’ve ceaselessly identified that the worldwide vitality imbalance (lower than 1 W/m2) equivalent to such small charges of warming is way smaller than the accuracy with which we all know the pure vitality flows (1 half in 300 or so), which implies Mom Nature could possibly be chargeable for the warming and we wouldn’t even understand it.

The Cheng (2017) dataset of Zero-2000m ocean warmth content material modifications extends the OHC document again to 1940 (with little international protection) and now up via 2019. The methodology of that dataset makes use of optimum interpolation methods to intelligently prolong the geographic protection of restricted knowledge. I’m not going to critique that methodology right here, and I agree with those that argue creating knowledge the place it doesn’t exist is just not the identical as having actual knowledge. As an alternative I wish to reply the query:

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If we take the 1940-2019 international OHC knowledge (in addition to noticed sea floor temperature knowledge) at face worth, and assume the entire warming development was human-caused, what does it suggest relating to equilibrium local weather sensitivity (ECS)?

Let’s assume ALL of the warming of the deep oceans since 1940 has been human-caused, and that the Cheng dataset precisely captures that. Moreover, let’s assume that the HadSST sea floor temperature dataset protecting the identical time frame can also be correct, and that the RCP radiative forcing situation utilized by the CMIP5 local weather fashions additionally represents actuality.

I up to date my 1D mannequin of ocean temperature with the Cheng knowledge in order that I might match its warming development over the 80-year interval 1940-2019. That mannequin additionally consists of El Nino and La Nina (ENSO) variability to seize year-to-year temperature modifications. The ensuing match I get with an assumed equilibrium local weather sensitivity of 1.85 deg. C is proven within the following determine.

0-2000m-Cheng-vs-model-1940-2019Fig. 1. Deep-ocean temperature variations 1940-2019 defined with a 2-layer vitality funds mannequin pressured with RCP6 radiative forcing situation and a mannequin local weather sensitivity of 1.85 deg. C. The mannequin additionally matches the 1940-2019 and 1979-2019 noticed sea floor temperature tendencies to about Zero.01 C/decade. If ENSO results are usually not included within the mannequin, the ECS is decreased to 1.7 deg. C.

Thus, primarily based upon primary vitality funds issues in a 2-layer ocean mannequin, we are able to clarify the IPCC-sanctioned international temperature datasets with a local weather sensitivity of only one.85 deg. C. And even that assumes that ALL of the warming is because of people which, as I discussed earlier than, is just not identified for the reason that international vitality imbalance concerned is way smaller than the accuracy with which we all know pure vitality flows.

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If I flip off the ENSO forcing I’ve within the mannequin, then after readjusting the mannequin free parameters to as soon as once more match the noticed temperature tendencies, I get about 1.7 deg. C local weather ECS. In that case, there are solely three mannequin adjustable parameters (ECS, the ocean prime layer thickness [18 m], and the assumed price or vitality change between the highest layer and the remainder of the Zero-2000m layer, [2.1 W/m2 per deg C difference in layer temperatures away from energy equilibrium]). In any other case, there are 7 mannequin adjustable parameters within the mannequin with ENSO results turned on.

For individuals who declare my mannequin is akin to John von Neumann’s well-known declare that with 5 variables he can match an elephant and make its trunk wiggle, I ought to level out that not one of the mannequin’s adjustable parameters (principally scaling components) fluctuate in time. They apply equally to every month-to-month time step from 1765 via 2019. The long-term habits of the mannequin when it comes to tendencies is especially ruled by (1) the assumed radiative forcing historical past (RCP6), (2) the assumed price of warmth storage (or extraction) within the deep ocean because the floor warms (or cools), and (three) the assumed local weather sensitivity, all inside an vitality funds mannequin with bodily items.

My conclusion is that the noticed tendencies in each floor and deep-layer temperature within the international oceans correspond to low local weather sensitivity, solely about 50% of what IPCC local weather fashions produce. This is identical conclusion as Lewis & Curry made utilizing related vitality funds issues, however utilized to 2 totally different averaging intervals about 100 years aside fairly than (as I’ve performed) in a time-dependent forcing-feedback mannequin.

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