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<div class="header reader-header reader-show-element"> <a
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href="https://www.theguardian.com/environment/2022/aug/01/climate-endgame-risk-human-extinction-scientists-global-heating-catastrophe">theguardian.com</a>
<h1 class="reader-title">Climate endgame: risk of human
extinction ‘dangerously underexplored’</h1>
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<address aria-label="Contributor info"
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<div class=" dcr-1mp5s8u"><a rel="author"
data-link-name="auto tag link"
href="https://www.theguardian.com/profile/damiancarrington">Damian
Carrington</a> Environment editor</div>
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<summary class="dcr-h56grb">Mon 1 Aug 2022 20.00 BST</summary>
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<div class="reader-estimated-time" dir="ltr">6-7 minutes</div>
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<p>The risk of global societal collapse or human
extinction has been “dangerously underexplored”, climate
scientists have warned in an analysis.</p>
<p>They call such a catastrophe the “climate endgame”.
Though it had a small chance of occurring, given the
uncertainties in future emissions and the climate
system, cataclysmic scenarios could not be ruled out,
they said.</p>
<p>“Facing a future of accelerating climate change while
blind to worst-case scenarios is naive risk management
at best and fatally foolish at worst,” the scientists
said, adding that there were “ample reasons” to suspect
global heating could result in an apocalyptic disaster.</p>
<p>The international team of experts argue the world needs
to start preparing for the possibility of the climate
endgame. “Analysing the mechanisms for these extreme
consequences could help galvanise action, improve
resilience, and inform policy,” they said.</p>
<p>Explorations in the 1980s of the nuclear winter that
would follow a nuclear war spurred public concern and
disarmament efforts, the researchers said. The analysis
proposes a research agenda, including what they call the
“four horsemen” of the climate endgame: famine, extreme
weather, war and disease.</p>
<p>They also called for the Intergovernmental Panel on
Climate Change to produce a special report on the issue.
The <a href="https://www.ipcc.ch/sr15/"
data-link-name="in body link">IPCC report on the
impacts of just 1.5C</a> of heating drove a
“groundswell of public concern”, they said.</p>
<p>“There are plenty of reasons to believe climate change
could become catastrophic, even at modest levels of
warming,” said Dr Luke Kemp at the University of
Cambridge’s Centre for the Study of Existential Risk,
who led the analysis. “Climate change has played a role
in every mass extinction event. It has helped fell
empires and shaped history.</p>
<p>“Paths to disaster are not limited to the direct
impacts of high temperatures, such as extreme weather
events. Knock-on effects such as financial crises,
conflict and new disease outbreaks could trigger other
calamities.”</p>
<p>The analysis is published in the journal <a
href="https://www.pnas.org/cgi/doi/10.1073/pnas.2108146119"
data-link-name="in body link">Proceedings of the
National Academy of Sciences</a> and was reviewed by a
dozen scientists. It argues that the consequences of
global heating beyond 3C have been underexamined, with
few quantitative estimates of the total impacts. “We
know least about the scenarios that matter most,” Kemp
said.</p>
<p>A thorough risk assessment would consider how risks
spread, interacted and amplified, but had not been
attempted, the scientists said. “Yet this is how risk
unfolds in the real world,” they said. “For example, a
cyclone destroys electrical infrastructure, leaving a
population vulnerable to an ensuing deadly heatwave.”
The Covid pandemic underlined the need to examine rare
but high-impact global risks, they added.</p>
<p>Particularly concerning are tipping points, where a
small rise in global temperature results in a big change
in the climate, such as huge carbon emissions from an
Amazon rainforest suffering major droughts and fires.
Tipping points could <a
href="https://www.theguardian.com/environment/2021/jun/03/climate-tipping-points-could-topple-like-dominoes-warn-scientists"
data-link-name="in body link">trigger others in a
cascade</a> and some remained little studied, they
said, such as the <a
href="https://www.nature.com/articles/s41561-019-0310-1.pdf?proof=t"
data-link-name="in body link">abrupt loss of
stratocumulus cloud decks</a> that could cause an
additional 8C of global warming.</p>
<p>The researchers warn that climate breakdown could
exacerbate or trigger other catastrophic risks, such as
international wars or infectious disease pandemics, and
worsen existing vulnerabilities such as poverty, crop
failures and lack of water. The analysis suggests
superpowers may one day fight over geoengineering plans
to reflect sunlight or the right to emit carbon.</p>
<p>“There is a striking overlap between currently
vulnerable states and future areas of extreme warming,”
the scientists said. “If current political fragility
does not improve significantly in the coming decades,
then a belt of instability with potentially serious
ramifications could occur.”</p>
<p>There were further good reasons to be concerned about
the potential of a global climate catastrophe, the
scientists said: “There are warnings from history.
Climate change has played a role in the <a
href="https://www.academia.edu/44322625/The_IPCC_A_Primer_for_Archaeologists"
data-link-name="in body link">collapse or
transformation of numerous previous societies</a> and
in each of the five mass extinction events in Earth’s
history.”</p>
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<p>New modelling in the analysis shows that extreme heat –
defined as an annual average temperature of more than
29C – could affect 2 billion people by 2070 if carbon
emissions continue.</p>
<p>“Such temperatures currently affect around 30 million
people in the Sahara and Gulf Coast,” said Chi Xu, at
Nanjing University in China, who was part of the team.
“By 2070, these temperatures and the social and
political consequences will directly affect two nuclear
powers, and seven maximum containment laboratories
housing the most dangerous pathogens. There is serious
potential for disastrous knock-on effects.”</p>
The current trend of greenhouse gas emissions would cause
a rise of 2.1-3.9C by 2100. But if existing pledges of
action are fully implemented, the range would be 1.9-3C.
Achieving all long-term targets set to date would mean
1.7-2.6C of warming.
<p>“Even these optimistic assumptions lead to dangerous
Earth system trajectories,” the scientists said.
Temperatures more than 2C above pre-industrial levels
had not been sustained on Earth for more than 2.6m
years, they said, far before the rise of human
civilisation, which had risen in a “narrow climatic
envelope” over the past 10,000 years.</p>
<p>“The more we learn about how our planet functions, the
greater the reason for concern,” said Prof Johan
Rockström, at the Potsdam Institute for Climate Impact
Research in Germany. “We increasingly understand that
our planet is a more sophisticated and fragile organism.
We must do the maths of disaster in order to avoid it.”</p>
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