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The direst potential impacts of the climate crisis for the UK have been outlined by researchers, encompassing a blistering 4C jump in temperatures to a 2-metre surge in sea levels. A separate possibility predicts a decline of 6C in temperatures following the failure of crucial Atlantic Ocean currents, which would severely impact food production and energy needs.

Possible Extremes, Not Forecasts

These consequences, some of which are connected to climate tipping points, are considered as unlikely but plausible. The researchers said that these projections addressed a shortfall in forecasting that had rendered the UK unprepared for worst-case results.

"The severe weather events we have detailed are not forecasts, but they are plausible," said Nigel Arnell who oversaw the analysis. "Britain has been making preparations lacking the frameworks to plan for worst-case scenarios. We've now provided decision-makers what they need to get ready for future conditions they hope never happen, but dare not dismiss."

A Spectrum of Harsh Climate Projections

Another collection of severe models sets out the projected severity of extreme weather between now and the year 2100. These indicate that thermometer readings could rocket in certain periods by up to 6C above historical levels, while precipitation could be three times typical amounts.

The chance of the extreme scenarios coming to pass remains uncertain due to uncertainty about what steps will be taken to combat global warming and how the planet's climate will react. This research was likened to national security risk assessments or stress tests for economic stability.

Major Possibility Elements

• Severe Heating: Worldwide averages exceeding 4C by 2100 could occur if emissions cuts breaks down or if powerful amplifying effects such as the Amazon basin perishing emit its huge repository of carbon. This would result in severe and lengthy heat domes and dry spells affecting the UK in summer.
• AMOC Shutdown: A major ocean current, the Atlantic meridional overturning circulation (Amoc), is slowing down and showing signs of collapse due to global heating. A collapse beginning in 2030 would lead to a six-degree temperature drop in the UK. "Farming would face immense difficulties and water supplies would be fundamentally reshaped," said the lead researcher.
• Rapid Sea Level Rise: A rise of 2.0-2.2 metres around the UK by 2100 could happen if glaciers in the polar regions melt abruptly, submerging low-lying areas. Differing from the other scenarios, this possibility is already known by coastal engineers.
• Pollution Paradox: Temperatures could also be pushed higher by about 0.75C if airborne particulates is drastically reduced. This paradoxical outcome occurs because pollution particles from fossil fuel combustion reflect sunlight from reaching the ground.

Preparing for the Worst

The severe models could be applied to guide the construction of long-term infrastructure, including new towns, energy plants and flood defences. Knowledge about these environmental threats could also hasten the push to cut fossil fuel emissions.

The research developed the worst-case scenarios using a blend of past data and records, digital projections and established principles. The scenarios omit potential global problems like the agricultural collapse and geopolitical instability.

The project was initiated as part of a government’s climate resilience programme. Independent analyses have stated that too little consideration was being paid to low‐likelihood but high‐impact risks.

Official experts has recommended that the UK needs to "prepare for two degrees of warming" and evaluate the dangers for four degrees. Earlier government strategies have been described as being "insufficient" by environmental groups.

A national response said: "Global warming is at the core of this government’s agenda, both adapting for the future and establishing itself as a low-carbon economy. It is crucial that the UK is prepared for the effects."