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The most severe possible consequences of the global heating for the UK have been mapped by researchers, ranging from a scorching 4C jump in mean temperatures to a 2-metre rise in ocean levels. Another scenario predicts a plunge of 6C in temperature following the shutdown of crucial Atlantic Ocean currents, which would severely impact agriculture and energy demand.

Credible Events, Not Predictions

These impacts, certain ones are associated with irreversible climate shifts, are viewed as low probability but credible. The researchers stated that these projections filled a gap in planning that had left the UK ill-prepared for extreme outcomes.

"The worst-case scenarios we have detailed should not be seen as certainties, but they are credible," stated the lead researcher who led the research. "The UK has been making preparations without the methods to plan for worst-case scenarios. We've now supplied decision-makers what they need to plan for environmental results they hope never happen, but can’t afford to ignore."

A Suite of Extreme Weather Projections

A second set of severe models maps the possible scale of severe conditions between now and the end of the century. These indicate that thermometer readings could soar in particular seasons by up to 6C above historical levels, while rainfall could be triple typical amounts.

The probability of the worst-case outcomes coming to pass cannot be precisely determined due to uncertainty about what action will be implemented to tackle climate change and how the climate system will react. This approach was described as similar to national security risk assessments or stress tests for financial systems.

Critical Possibility Details

• 4C Temperature Rise: Global temperatures soaring past 4C by 2100 could occur if international cooperation breaks down or if powerful amplifying effects including the Amazon rainforest perishing unleash its vast reserves of carbon. This would cause extreme and prolonged heat domes and dry spells plaguing the UK in summer.
• AMOC Shutdown: A key circulation system, the AMOC, is weakening and showing signs of collapse due to ocean warming. A collapse commencing by 2030 would lead to a 6C cooling in the UK. "Agriculture would face immense difficulties and water resources would be drastically changed," noted Arnell.
• Rapid Sea Level Rise: A increase of 2.0-2.2 metres around the UK by 2100 could happen if glaciers in the polar regions disintegrate quickly, inundating low-lying areas. Unlike the other scenarios, this threat is already recognized by infrastructure experts.
• Pollution Paradox: Global averages could also be driven up by about 0.75C if industrial aerosols is rapidly cleaned up. This unexpected result occurs because tiny specks from industrial activity scatter sunlight from reaching the ground.

Preparing for the Worst

The worst-case scenarios could be used to inform the construction of critical national infrastructure, including expanded cities, energy plants and flood defences. Knowledge about these future hazards could also speed the transition to slash carbon pollution.

The analysis formulated the worst-case scenarios using a blend of past data and records, digital projections and scientific theory. These outcomes exclude broader worldwide issues including the global food shortages and geopolitical instability.

This work was commissioned as part of a government’s climate resilience programme. Independent analyses have stated that too little consideration was being allocated to catastrophic yet improbable risks.

The government's climate advisors has stated that the UK needs to "adapt to 2C" and evaluate the risks for severe warming. Earlier government strategies have been criticised as being "inadequate" by some observers.

An official statement commented: "The climate emergency is at the core of the country's focus, both preparing for impacts and becoming a low-carbon economy. It is crucial that the UK is resilient for the consequences."