The world must prepare for a “climate endgame” to better understand and plan for the potentially catastrophic effects of global warming, which governments have yet to consider, scientists warned Tuesday.
Climate models that can predict the magnitude of global warming as a function of greenhouse gas emissions are becoming more sophisticated, providing policymakers with an accurate trajectory of global temperature rise.
Less well understood are the cascading effects of certain events, such as crop failures and infrastructure losses due to extreme weather events, which become more likely with each degree of warming.
Researchers from the University of Cambridge and the Potsdam Institute for Climate Impact Research (PIK) outlined what is currently known about “catastrophic consequences” and identified gaping knowledge gaps.
In the journal Proceedings of the National Academy of Science, they proposed an international research agenda to help governments plan for “bad to worst cases.”
This included four main areas of concern – what the authors called the “Four Horsemen” of climate change: famine and malnutrition, extreme weather, conflict and vector-borne diseases.
“Irreversible and potentially catastrophic risks posed by human-caused climate change must be factored into our planning and actions,” said Johan Rockstrom, PIK Director and co-author of the study.
He said that as more research is done on Earth’s climate tipping points — such as the irreversible melting of the ice caps or the Amazon rainforest turning from a carbon sink into a source — shows the ever-increasing need to incorporate high-risk scenarios into climate modeling .
“The key is to calculate the disaster to avoid it,” he said.
– “Mismatched Caution” –
The authors noted that successive UN climate science reports have focused mainly on the projected impact of 1.5°C to 2°C of warming and have largely ignored the possibility of excessive temperature rise.
Government plans call for the Earth to rise by up to 2.7°C this century, far from the 1.5°C cap envisaged in the 2015 Paris Climate Agreement.
The study suggests that a scientific tendency to “err on the side of the least drama” has led to a lack of focus on potential impacts of warming of 3°C or more.
“This caution is understandable, but it is inconsistent with the risks and potential harms that climate change poses,” it said.
Furthermore, risk assessments for so-called low-probability, high-impact events are notoriously difficult to incorporate into long-term climate models.
The researchers calculated that areas of extreme heat – with an annual average temperature above 29°C – could blanket two billion people by 2070.
They warned that temperatures posed a major risk of multiple “breadbasket failures” due to droughts like that in western Europe and heatwaves like the one that hit India’s wheat crop in March-April.
The team called for a special UN science report focusing on “catastrophic climate change scenarios,” similar to its 2018 report of 1.5C warming.
“We need to get serious about understanding the profound risks involved in shifting our planet into uncharted territory,” said Joeri Rogelj, research director at Imperial College London’s Grantham Institute, who was not involved in the study.
“Researching these extreme cases means we can prepare better, including by being more serious about reducing emissions now.”
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