Recent global warming trends are inconsistent with very high climate sensitivity

Date:
August 18, 2020
Source:
University of Exeter
Summary:
New research reports that the most sensitive climate models
overestimate global warming during the last 50 years.



FULL STORY ========================================================================== Research published this week in Earth System Dynamics reports that the
most sensitive climate models overestimate global warming during the
last 50 years.


========================================================================== Three scientists from the University of Exeter studied the output of
complex climate models and compared them to temperature observations
since the 1970s.

Recent developments in cloud modelling have produced models that portray
very large sensitivity to rising greenhouse gas concentrations.

A subset of models even showed that a doubling of CO2 could lead to over
5DEGC of warming, questioning whether the goals of the Paris agreement
are achievable even if nations do everything they can.

The lead author of the study, PhD candidate Femke Nijsse from the
University of Exeter, said: "In evaluating the climate models we were able
to exploit the fact that thanks to clean air regulation, air pollution in
the form of climate- cooling aerosols have stopped increasing worldwide, allowing the greenhouse gas signal to dominate recent warming."
The amount of warming that occurs after CO2 concentrations in the
atmosphere are doubled is called the equilibrium climate sensitivity.



==========================================================================
The study found that based on the latest generation of climate models
the equilibrium climate sensitivity is likely between 1.9 and 3.4 DEGC.

Co-author Mark Williamson, of Exeter's Global Systems Institute, added:
"Global warming since 1970 also provides even better guidance on the
rate of climate change in the future.

"We find a likely range for the 'Transient Climate Response' of
1.3-2.1DEGC, whether we use the latest models or the previous generation
of models." The new study is only one piece of the puzzle.

A recent review paper found that low estimates of climate sensitivity
can be excluded because they are, in general, not consistent with climate changes in Earth's past.

Co-author Professor Peter Cox explains the significance of these
findings: "It is good to see that studies are now converging on a range
of equilibrium climate sensitivity, and that both high and low values
can be excluded.

"For over forty years, climate scientists have tried to pinpoint this
quantity and it seems that we're finally getting close." The research
was supported by the European Research Council ('ECCLES' project).


========================================================================== Story Source: Materials provided by University_of_Exeter. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Femke J. M. M. Nijsse, Peter M. Cox, Mark S. Williamson. Emergent
constraints on transient climate response (TCR) and equilibrium
climate sensitivity (ECS) from historical warming in CMIP5 and
CMIP6 models.

Earth System Dynamics, 2020; 11 (3): 737 DOI:
10.5194/esd-11-737-2020 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200818103820.htm

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