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The most severe potential impacts of the climate crisis for the UK have been outlined by scientists, including a searing 4C rise in average temperatures to a 2-metre rise in sea level. Another scenario foresees a drop of 6C in temperature following the shutdown of crucial Atlantic Ocean currents, which would massively disrupt food production and energy demand.

Plausible Events, Not Forecasts

These impacts, certain ones are associated with climate tipping points, are seen as unlikely but credible. The scientists explained that these scenarios filled a gap in planning that had left the UK ill-prepared for extreme outcomes.

"The climate extremes we have mapped should not be seen as certainties, but they are possible," commented the lead researcher who led the analysis. "The UK has been making preparations lacking the tools to plan for catastrophic outcomes. We've now provided decision-makers what they need to prepare for environmental results they wish to avoid, but dare not dismiss."

A Range of Severe Conditions Projections

A further series of dire projections details the potential extent of harsh climate between now and the end of the century. These show that thermometer readings could rocket in some months by up to 6C higher than historical levels, while precipitation could be 300% of normal levels.

The probability of the extreme scenarios occurring could not be calculated due to uncertainty about what steps will be enacted to address global heating and how the climate system will behave. This analysis was compared to security threat evaluations or scenario planning for economic stability.

Major Possibility Elements

• Four-Degree Warming: Global temperatures rising well above 4C by 2100 could transpire if emissions cuts breaks down or if strong feedback loops like the tropical forests dying release its vast reserves of carbon. This would lead to severe and lengthy heatwaves and water shortages hitting the UK in summer.
• AMOC Shutdown: A critical sea current, the AMOC, is losing strength and losing stability due to global heating. A full shutdown starting around 2030 would lead to a six-degree temperature drop in the UK. "Crop production would be severely challenged and water resources would be completely altered," explained Arnell.
• Rapid Sea Level Rise: A increase of 2.0-2.2 metres around the UK by 2100 could occur if polar ice in Greenland and Antarctica disintegrate quickly, submerging low-lying areas. In contrast to the other scenarios, this threat is already recognized by planners.
• Aerosol Effect: Temperatures could also be increased by about 0.75C if pollution from industry is drastically reduced. This counterintuitive effect occurs because tiny specks from fossil fuel combustion scatter solar radiation from reaching the ground.

Planning for the Unthinkable

These dire projections could be applied to guide the building of long-term infrastructure, such as expanded cities, nuclear power stations and flood defences. Understanding these climate risks could also speed the push to slash greenhouse gas emissions.

The research created the extreme models using a blend of observed and historical experience, computer simulations and established principles. The possibilities omit international cascading effects like the global food shortages and increased conflict.

This work was initiated as part of a government’s risk assessment framework. Independent analyses have cautioned that insufficient focus was being given to catastrophic yet improbable risks.

Official experts has said that the UK must "become resilient to moderate heating" and assess the dangers for severe warming. Previous adaptation plans have been criticised as being "very weak" by certain experts.

A national response said: "Global warming is at the core of our national priorities, both building resilience and becoming a low-carbon economy. It is crucial that the UK is prepared for the effects."