New climate pledges, if fulfilled, now significantly more likely to
prevent worst of global warming

Date:
November 4, 2021
Source:
DOE/Pacific Northwest National Laboratory
Summary:
New climate pledges issued ahead of COP26 boost the chances of
limiting global warming to 2 degrees, according to a new study.



FULL STORY ==========================================================================
Over 100 nations have issued new commitments to reduce greenhouse gas
emissions ahead of the United Nations Conference of the Parties, or COP26, currently underway in Glasgow, Scotland.


==========================================================================
A new analysis published today in the journal Science assessed those new pledges, or nationally determined commitments (NDCs), and how they could
shape Earth's climate. The study's authors find the latest NDCs could
chart a course where limiting global warming to 2 degrees Celsius (3.6
degrees Fahrenheit) and under within this century is now significantly
more likely.

Under pledges made at the 2015 Paris Agreement, the chances of limiting temperature change to below 2 and 1.5 degrees Celsius (2.7 degrees
Fahrenheit) by 2100 were 8 and 0 percent, respectively.

Under the new pledges -- and if those pledges are successfully fulfilled
and reinforced with policies and measures of equal or greater ambition
-- the study's authors estimate those chances now rise to 34 and 1.5
percent, respectively. If countries strike a more ambitious path beyond
2030, those probabilities become even more likely, rising to 60 and 11
percent, respectively.

Further, the chance of global temperatures rising above 4 degrees Celsius
(7.2 degrees Fahrenheit) could be virtually eliminated. Under the 2015
pledges, the probability of such warming was, at 10 percent, more likely.

"We are so much closer to getting to the 2-degree goal than six years
ago when the Paris Agreement was first signed," said corresponding author Haewon McJeon, a research scientist at the Department of Energy's Pacific Northwest National Laboratory. "The wave of strengthened climate pledges
and net-zero targets significantly increased our chance of staying under 2 degrees Celsius. And we practically ruled out the possibility of the worst climate outcomes of 4 degrees or higher." But making the 1.5 degrees
Celsius limit more likely will take more ambition, cautioned lead author
Yang Ou, a postdoctoral researcher at the Joint Global Change Research Institute, a partnership between PNNL and the University of Maryland.



==========================================================================
"We find there's a roughly one in three chance that we'll stay under
2 degrees Celsius," said Ou. "But even with increased ambition, we're
still far away from getting down to 1.5 degrees in this century."
The researchers used an open-source model called the Global Change
Analysis Model (GCAM) to simulate a spectrum of emissions scenarios. They
then evaluated the probabilistic temperature outcomes for those scenarios.

At one end of the spectrum is a hypothetical future in which current
climate mitigation measures and policies remain largely the same through
2100. At the other, nations commit to more ambitious targets for limiting emissions and increasing the global decarbonization rate. Such modeling illustrates the range of climate outcomes that lie beyond different
courses of action.

The Road Ahead Several factors reshaped near-term emissions trajectories
and long-term climate outcomes, the authors said. Examples include the worldwide shift away from coal to technological advances that made solar
panels and electric vehicles less costly. These developments, they said,
have helped bring the goals of the Paris Agreement closer to fruition.



==========================================================================
Even under a scenario in which no new emission mitigation policies take
place through 2100, this century's emissions are projected to be lower
than previous estimates, largely due to post-2015 developments like
reduced coal power investment and the reduced cost of renewable energy.

"New commitments, technological advances, and the near- and long-term
recovery from the pandemic have set us on a different course than what
laid before us at the 2015 Paris Agreement," said co-lead author and
PNNL research scientist Gokul Iyer. "But if we adopt more ambitious
goals that truly reflect the common but differentiated responsibilities
across all parties, that gives us a better than even chance of staying
under 2 degrees Celsius." "And this highlights the importance of the
Glasgow meeting," Iyer added.

"Without periodic and transparent updates, we won't get the commitments
strong enough to meet the temperature goal." The research team
brought together researchers from PNNL with researchers from the
U.S. Environmental Protection Agency, Climate Action Tracker, the
University of Maryland, the University of Melbourne, and Imperial
College London.

"This was an all-out team effort among the scientists and policy
experts with extensive knowledge of ongoing international discussions
on climate policies," McJeon added. "We brought together the policy
analysts who track each country's climate commitments with the modelers
who simulate global greenhouse gas emission activities and the climate
response to these increased emissions. It really shows the importance
of collaborative science." This assessment, Can Updated Climate Pledges
Limit Warming Well Below 2DEGC, was supported by the U.S. Environmental Protection Agency and the German Federal Ministry for the Environment,
Nature Conservation and Nuclear Safety.

========================================================================== Story Source: Materials provided by
DOE/Pacific_Northwest_National_Laboratory. Original written by Brendan
Bane. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Yang Ou, Gokul Iyer, Leon Clarke, Jae Edmonds, Allen A. Fawcett,
Nathan
Hultman, James R. McFarland, Matthew Binsted, Ryna Cui, Claire
Fyson, Andreas Geiges, Sofia Gonzales-Zun~iga, Matthew J. Gidden,
Niklas Ho"hne, Louise Jeffery, Takeshi Kuramochi, Jared Lewis,
Malte Meinshausen, Zebedee Nicholls, Pralit Patel, Shaun Ragnauth,
Joeri Rogelj, Stephanie Waldhoff, Sha Yu, Haewon McJeon. Can
updated climate pledges limit warming well below 2DEGC? Science,
2021; 374 (6568): 693 DOI: 10.1126/ science.abl8976 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211104162551.htm

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