World dangerously unprepared for worst-case 'climate endgame' scenarios, say scientists

The world has already warmed 1.2 deg C and is on course to reach 1.5 deg C by the next decade. PHOTO: REUTERS

SINGAPORE - The world is blind to the worst-case scenarios of climate change that could trigger societal collapse, even extinction, an analysis by an international group of scientists says, describing it as a "dangerously underexplored topic".

In their analysis, released on Monday (Aug 1), the authors said there was an urgent need to study what they call the "climate endgame", namely low-risk but high-impact outcomes of climate change that could threaten the existence of humanity.

"Facing a future of accelerating climate change while blind to worst-case scenarios is naive risk management at best and fatally foolish at worst," they said in the study.

"The climate endgame agenda is intended to both help inform resilience and policy efforts that would avert breakdown and inform debates over emergency responses," lead author, Dr Luke Kemp, from Cambridge University's Centre for the Study of Existential Risk, told The Straits Times.

The authors said climate change has played a role in every mass extinction event and it has helped fell empires.

"There is ample evidence that climate change could become catastrophic. We could enter such endgames at even modest levels of warming," the authors said in the study, which was published in the Proceedings Of The National Academy of Sciences journal.

The analysis comes as extreme heatwaves, wildfires and floods killed thousands and triggered widespread concerns about the rapid march of climate change, which is being driven mainly by the burning of fossil fuels.

The scientists propose a research agenda focusing on what they call the "four horsemen" of the climate endgame: famine and malnutrition, extreme weather, conflict, and vector-borne diseases.

Over recent decades, there has been intensive study of the impacts of increasing temperatures, the authors said. But there has been less study into how impacts such as floods or droughts could cascade into other events, such as conflict over resources or financial crises.

Research has also tended to focus on the impacts of global warming of 1.5 deg C and 2 deg C above pre-industrial levels. Yet, there is still uncertainty over future temperature rises, and the higher the temperatures, the greater the risks.

The authors put global warming of 3 deg C or more by the end of the century as a marker for extreme climate change. The world has already warmed 1.2 deg C, and is on course to reach 1.5 deg C by the next decade.

Even without considering worst-case climate responses, the current trajectory puts the world on track for a temperature rise of between 2.1 deg C and 3.9 deg C by 2100, they said, underscoring the need to make rapid and deep emissions cuts to reduce future threats.

Climate change could reinforce other interacting threats, including rising inequality, demographic stresses, misinformation and new destructive weapons.

Detailed risk assessment would need to consider how risks spread, interact, amplify and are aggravated by human responses, the authors said.

They added that there is a need to understand how risk unfolds in the real world.

For example, rising temperatures pose a major threat to global food supplies, with increasing probabilities of "breadbasket failures" in some of the world's most agriculturally productive areas, the authors said.

Hotter and more extreme weather could also create conditions for new disease outbreaks as shrinking habitats bring people and wildlife into closer contact.

Another concern is that the most vulnerable states and communities will continue to be the hardest hit in a warming world, exacerbating inequities.

Computing modelling used in the analysis showed that two billion people could be affected by extreme heat - an annual average temperature of more than 29 deg C - if carbon emissions keep rising.

Currently, only 30 million people live in hot places, primarily in the Sahara Desert and Gulf Coast.

"If current political fragility does not improve significantly in the coming decades, then a belt of instability with potentially serious ramifications could occur," the authors said.

Perhaps one of the greatest concerns is what are called tipping points, sudden changes that could accelerate climate change.

These include arctic permafrost thawing, releasing huge amounts of methane (a powerful greenhouse gas) and carbon dioxide; carbon loss due to intense droughts and fires in the Amazon rainforest; as well as a sudden collapse of ice sheets in West Antarctica, which could dramatically raise sea levels.

Dr Kemp said there were a number of reasons why catastrophic risks have not been fully assessed to date.

"Higher-temperature scenarios and more complex risk assessments are simply harder to do."

The clout of the fossil fuel industry and other "merchants of doubt" has also led to scientists erring on the side of least drama, he added.

"The same is likely true of our risk assessments: Looking at plausible catastrophic scenarios is sane risk management, but would likely face political opposition from the forces causing climate change."

Find out more about climate change and how it could affect you on the ST microsite here.