Climate endgame: risk of human extinction
‘dangerously underexplored’
Scientists say there are ample reasons to suspect
global heating could lead to catastrophe
Damian
Carrington Environment editor
Mon 1 Aug
2022 20.00 BST
The risk of
global societal collapse or human extinction has been “dangerously
underexplored”, climate scientists have warned in an analysis.
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.
“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.
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.
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.
They also
called for the Intergovernmental Panel on Climate Change to produce a special
report on the issue. The IPCC report on the impacts of just 1.5C of heating
drove a “groundswell of public concern”, they said.
“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.
“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.”
The
analysis is published in the journal Proceedings of the National Academy of
Sciences 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.
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.
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 trigger
others in a cascade and some remained little studied, they said, such as the
abrupt loss of stratocumulus cloud decks that could cause an additional 8C of
global warming.
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.
“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.”
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 collapse or transformation of numerous previous
societies and in each of the five mass extinction events in Earth’s history.”
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.
“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.”
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.
“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.
“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.”
.jpg)
.jpg)
Sem comentários:
Enviar um comentário