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The direst possible consequences of the global heating for the UK have been detailed by scientists, encompassing a scorching 4C rise in mean temperatures to a 2-metre increase in sea levels. A separate possibility envisions a decline of 6C in temperatures following the failure of key Atlantic Ocean currents, which would severely impact food production and energy demand.

Credible Outcomes, Not Guarantees

These effects, a number of which are associated with irreversible climate shifts, are viewed as unlikely but plausible. The researchers explained that these projections filled a gap in risk assessment that had left the UK not ready for worst-case results.

"The climate extremes we have mapped aren’t predictions, but they are possible," stated Nigel Arnell who directed the research. "The UK has been formulating policy without the frameworks to assess worst-case scenarios. We've now given decision-makers what they need to plan for future conditions they wish to avoid, but can’t afford to ignore."

A Suite of Severe Conditions Projections

A further series of worst-case scenarios sets out the potential extent of extreme weather between now and the end of the century. These suggest that thermometer readings could skyrocket in particular seasons by up to 6C above historical levels, while precipitation could be three times typical amounts.

The probability of the extreme scenarios coming to pass remains uncertain due to a lack of certainty about what action will be implemented to tackle global warming and how the climate system will behave. This analysis was likened to security threat evaluations or scenario planning for economic stability.

Major Scenario Elements

• 4C Temperature Rise: Global temperatures rising well above 4C by 2100 could transpire if emissions cuts breaks down or if strong feedback loops such as the tropical forests dying unleash its huge repository of carbon. This would cause extreme and prolonged heatwaves and droughts plaguing the UK in summer.
• Ocean Circulation Failure: A major ocean current, the North Atlantic current, is weakening and showing signs of collapse due to ocean warming. A collapse beginning in 2030 would lead to a 6C cooling in the UK. "Farming would face immense difficulties and water supplies would be fundamentally reshaped," noted the professor.
• Sudden Ocean Inundation: A surge of 2.0-2.2 metres around the UK by 2100 could happen if polar ice in the polar regions collapse rapidly, inundating low-lying areas. Differing from the other scenarios, this possibility is already understood by infrastructure experts.
• Aerosol Effect: Global averages could also be increased by about 0.75C if pollution from industry is sharply cut. This paradoxical outcome occurs because aerosol particles from fossil fuel combustion block sunlight from reaching the ground.

Building Resilience Against the Worst

These dire projections could be applied to guide the building of long-term infrastructure, for example housing developments, nuclear power stations and flood defences. Understanding these climate risks could also accelerate the push to cut carbon pollution.

The research developed the extreme models using a blend of past data and records, climate models and established principles. The scenarios omit potential global problems including the global food shortages and geopolitical instability.

The project was requested as part of a official climate resilience programme. Independent analyses have stated that not enough attention was being allocated to catastrophic yet improbable risks.

Official experts has stated that the UK must "adapt to 2C" and assess the risks for severe warming. Past policy documents have been criticised as being "insufficient" by environmental groups.

A national response commented: "Climate change is at the heart of the country's focus, both building resilience and establishing itself as a renewable energy leader. It is essential that the UK is prepared for the consequences."