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The gravest possible consequences of the climate crisis for the UK have been mapped by researchers, including a blistering 4C rise in mean temperatures to a 2-metre rise in sea level. A separate possibility predicts a drop of 6C in temperature following the collapse of key Atlantic Ocean currents, which would severely impact food production and energy demand.

Possible Extremes, Not Predictions

These consequences, certain ones are associated with climate tipping points, are viewed as improbable but credible. The team said that these projections plugged a hole in risk assessment that had left the UK not ready for catastrophic possibilities.

"The worst-case scenarios we have outlined should not be seen as certainties, but they are possible," said the lead researcher who led the analysis. "Britain has been formulating policy lacking the frameworks to plan for extreme possibilities. We've now provided planners what they need to get ready for climate outcomes they hope never happen, but can’t afford to ignore."

A Range of Extreme Weather Scenarios

Another collection of dire projections details the potential extent of harsh climate between now and the end of the century. These suggest that thermometer readings could soar in some months by up to 6C above average, while rainfall could be three times typical amounts.

The chance of the worst-case outcomes coming to pass cannot be precisely determined due to unknown factors about what steps will be taken to address global warming and how the Earth's systems will behave. This research was described as similar to national security risk assessments or stress tests for economic stability.

Key Outcome Details

• Severe Heating: Global temperatures exceeding 4C by 2100 could occur if international cooperation collapses or if strong feedback loops such as the Amazon basin dying emit its huge repository of carbon. This would cause intense and enduring heat domes and water shortages plaguing the UK in summer.
• Ocean Circulation Failure: A key circulation system, the AMOC, is weakening and losing stability due to climate change. A full shutdown beginning in 2030 would lead to a six-degree temperature drop in the UK. "Crop production would be severely challenged and water supplies would be completely altered," said Arnell.
• Rapid Sea Level Rise: A increase of 2.0-2.2 metres around the UK by 2100 could occur if polar ice in the polar regions disintegrate quickly, submerging low-lying areas. Unlike the other scenarios, this risk is already understood by infrastructure experts.
• Aerosol Effect: Global averages could also be pushed higher by about 0.75C if pollution from industry is sharply cut. This unexpected result occurs because aerosol particles from fossil fuel combustion reflect solar radiation from reaching the ground.

Planning for the Worst

The severe models could be applied to guide the building of critical national infrastructure, including housing developments, power generation facilities and water management networks. Knowledge about these climate risks could also accelerate the drive to slash fossil fuel emissions.

The analysis developed the extreme models using a blend of real-world events, computer simulations and scientific theory. The scenarios do not take into account broader worldwide issues including the agricultural collapse and increased conflict.

The project was commissioned as part of a official risk assessment framework. Independent analyses have stated that insufficient focus was being paid to high-consequence, low-probability risks.

The government's climate advisors has stated that the UK must "adapt to 2C" and assess the threats for severe warming. Earlier government strategies have been criticised as being "inadequate" by environmental groups.

A national response noted: "Global warming is at the center of our national priorities, both preparing for impacts and becoming a clean energy superpower. It is vital that the UK is prepared for the consequences."