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The most severe possible consequences of the climate crisis for the UK have been mapped by scientists, ranging from a blistering 4C increase in average temperatures to a two-metre rise in ocean levels. A separate possibility predicts a decline of 6C in temperatures following the failure of critical Atlantic Ocean currents, which would profoundly upset farming and energy needs.

Plausible Outcomes, Not Forecasts

These consequences, certain ones are connected to climate tipping points, are seen as improbable but plausible. The team stated that these scenarios addressed a shortfall in risk assessment that had rendered the UK ill-prepared for catastrophic possibilities.

"The climate extremes we have mapped should not be seen as certainties, but they are credible," stated Nigel Arnell who directed the research. "The nation has been planning without the methods to plan for worst-case scenarios. We've now provided decision-makers what they need to plan for climate outcomes they hope never happen, but must not overlook."

A Suite of Extreme Weather Possibilities

A second set of dire projections sets out the possible scale of harsh climate between now and the end of the century. These suggest that temperatures could skyrocket in particular seasons by up to 6C higher than historical levels, while rainfall could be triple typical amounts.

The likelihood of the worst-case outcomes coming to pass remains uncertain due to a lack of certainty about what measures will be implemented to combat global warming and how the planet's climate will react. This approach was compared to security threat evaluations or stress tests for the banking sector.

Critical Possibility Highlights

• Severe Heating: Planetary heating rising well above 4C by 2100 could transpire if international cooperation breaks down or if powerful amplifying effects such as the tropical forests dying release its enormous store of carbon. This would result in severe and lengthy heat domes and dry spells plaguing the UK in summer.
• Ocean Circulation Failure: A critical sea current, the AMOC, is weakening and losing stability due to ocean warming. A collapse beginning in 2030 would lead to a drastic cooling in the UK. "Farming would be severely challenged and freshwater availability would be completely altered," noted the professor.
• Rapid Sea Level Rise: A rise of 2.0-2.2 metres around the UK by 2100 could occur if glaciers in Greenland and Antarctica melt abruptly, submerging low-lying areas. Unlike the other scenarios, this possibility is already understood by infrastructure experts.
• Pollution Paradox: Temperatures could also be pushed higher by about 0.75C if airborne particulates is rapidly cleaned up. This counterintuitive effect occurs because aerosol particles from fossil fuel combustion scatter solar radiation from warming the ground.

Planning for the Extreme

The worst-case scenarios could be utilized in planning the building of major projects, such as expanded cities, energy plants and flood defences. Knowledge about these future hazards could also hasten the drive to slash greenhouse gas emissions.

The research developed the worst-case scenarios using a blend of past data and records, climate models and established principles. The scenarios exclude potential global problems like the global food shortages and increased conflict.

This work was requested as part of a national adaptation planning initiative. Previous assessments have stated that not enough attention was being allocated to catastrophic yet improbable risks.

Official experts has stated that the UK must "prepare for two degrees of warming" and evaluate the risks for four degrees. Previous adaptation plans have been labeled being "insufficient" by certain experts.

A national response said: "Climate change is at the center of the country's focus, both preparing for impacts and becoming a clean energy superpower. It is vital that the UK is ready for the effects."