New data imply slower global warming


Leaving aside whether ‘climate sensitivity’ (to carbon dioxide) is a valid concept in the first place, it’s been obvious for a while that climate modellers have seriously overestimated the actual level of any warming that has occurred in recent years. If that doesn’t suggest to them that something is wrong, what would?
H/T The GWPF

London, 24 April — A paper just published by the Journal of Climate concludes that high estimates of future global warming from most computer climate simulations are inconsistent with observed warming since 1850. The implication is that future warming will be 30 to 45% lower than suggested by the simulations.

The study estimates climate sensitivity — how much the world will warm when carbon dioxide levels increase* — from changes in observed temperatures and estimates of the warming effect of greenhouse gases and other drivers of climate change, from the mid/late 19th century until 2016.

The paper also addresses previous criticisms of the methodology used, finding that these are unfounded.

Nicholas Lewis explains:
“Our results imply that, for any future emissions scenario, future warming is likely to be substantially lower than the central computer model-simulated level projected by the IPCC, and highly unlikely to exceed that level.”

Nicholas Lewis adds:
“Our new sensitivity estimates are slightly lower than those obtained in a predecessor study published several years ago, despite the inclusion of the strong 2015–16 El Niño warming. Importantly, the upper uncertainty bounds of the new estimates are much lower.”

Highlights here.

ECS assumption:
*Two standard metrics summarize the sensitivity of global surface temperature to an externally imposed radiative forcing. Equilibrium climate sensitivity (ECS) represents the change in temperature to a doubling of atmospheric CO2 concentration once the deep ocean has reached equilibrium. The transient climate response (TCR), a shorter-term measure over 70 years, represents warming at the time CO2 concentration has doubled when it is increased by 1% a year.

via Tallbloke’s Talkshop

https://ift.tt/2FcwrUt

April 24, 2018 at 04:39AM

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