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The most severe potential impacts of the climate crisis for the UK have been mapped by researchers, including a blistering 4C rise in average temperatures to a 6.5-foot rise in sea levels. A separate possibility envisions a drop of 6C in temperatures following the failure of key Atlantic Ocean currents, which would severely impact food production and energy needs.

Credible Events, Not Guarantees

These effects, certain ones are linked to irreversible climate shifts, are seen as improbable but possible. The researchers stated that these projections filled a gap in risk assessment that had left the UK ill-prepared for worst-case results.

"The climate extremes we have detailed should not be seen as certainties, but they are credible," stated the professor who led the analysis. "The UK has been formulating policy in the absence of the methods to plan for extreme possibilities. We've now supplied planners what they need to get ready for environmental results they wish to avoid, but dare not dismiss."

A Suite of Extreme Weather Scenarios

A further series of severe models details the possible scale of harsh climate between now and the end of the century. These suggest that temperatures could soar in some months by up to 6C higher than historical levels, while rainfall could be three times normal levels.

The likelihood of the extreme scenarios happening cannot be precisely determined due to a lack of certainty about what measures will be implemented to combat climate change and how the planet's climate will behave. This analysis was likened to security threat evaluations or scenario planning for economic stability.

Major Outcome Elements

• Severe Heating: Global temperatures soaring past 4C by 2100 could transpire if emissions cuts fails or if strong feedback loops like the tropical forests becoming a net carbon source release its vast reserves of carbon. This would cause severe and lengthy heatwaves and droughts hitting the UK in summer.
• Atlantic Current Collapse: A major ocean current, the AMOC, is losing strength and becoming unstable due to ocean warming. A full shutdown starting around 2030 would lead to a six-degree temperature drop in the UK. "Farming would face immense difficulties and water resources would be completely altered," explained Arnell.
• Accelerated Coastal Flooding: A increase of 2.0-2.2 metres around the UK by 2100 could take place if ice sheets in Greenland and Antarctica disintegrate quickly, flooding coastal cities and towns. In contrast to the other scenarios, this risk is already known by coastal engineers.
• Aerosol Effect: Global averages could also be pushed higher by about 0.75C if industrial aerosols is drastically reduced. This unexpected result occurs because tiny specks from fossil fuel combustion reflect solar radiation from warming the ground.

Planning for the Worst

The severe models could be used to inform the development of critical national infrastructure, including housing developments, energy plants and flood defences. Understanding these climate risks could also speed the drive to slash fossil fuel emissions.

The analysis developed the severe projections using a blend of observed and historical experience, computer simulations and climate physics. The scenarios exclude broader worldwide issues like the global food shortages and geopolitical instability.

The project was commissioned as part of a official adaptation planning initiative. Earlier reports have cautioned that too little consideration was being allocated to high-consequence, low-probability risks.

Official experts has said that the UK needs to "adapt to 2C" and examine the dangers for four degrees. Earlier government strategies have been criticised as being "insufficient" by environmental groups.

A national response said: "Global warming is at the center of the country's focus, both adapting for the future and establishing itself as a low-carbon economy. It is crucial that the UK is ready for the impacts."