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The direst possible consequences of the climate emergency for the UK have been detailed by scientists, encompassing a blistering 4C jump in average temperatures to a 6.5-foot surge in sea levels. A separate possibility predicts a drop of 6C in temperature following the shutdown of critical Atlantic Ocean currents, which would massively disrupt food production and energy demand.

Credible Outcomes, Not Guarantees

These impacts, some of which are linked to irreversible climate shifts, are considered as improbable but credible. The researchers explained that these models addressed a shortfall in risk assessment that had left the UK not ready for extreme outcomes.

"The worst-case scenarios we have outlined should not be seen as certainties, but they are credible," stated Nigel Arnell who directed the analysis. "The nation has been planning without the frameworks to assess worst-case scenarios. We've now provided policymakers what they need to get ready for environmental results they hope never happen, but can’t afford to ignore."

A Spectrum of Extreme Weather Possibilities

Another collection of dire projections maps the potential extent of severe conditions between now and the end of the century. These suggest that thermometer readings could rocket in some months by up to 6C higher than historical levels, while rainfall could be 300% of normal levels.

The probability of the catastrophic events happening could not be calculated due to unknown factors about what action will be enacted to address global warming and how the Earth's systems will behave. This approach was described as similar to defence planning or resilience checks for the banking sector.

Major Possibility Highlights

• Four-Degree Warming: Planetary heating rising well above 4C by 2100 could transpire if international cooperation fails or if powerful amplifying effects such as the tropical forests dying release its enormous store of carbon. This would lead to severe and lengthy heat domes and droughts affecting the UK in summer.
• Atlantic Current Collapse: A major ocean current, the Atlantic meridional overturning circulation (Amoc), is slowing down and losing stability due to ocean warming. A collapse commencing by 2030 would lead to a six-degree temperature drop in the UK. "Crop production would struggle enormously and water resources would be completely altered," noted the professor.
• 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 coastal cities and towns. Differing from the other scenarios, this possibility is already known by infrastructure experts.
• Pollution Paradox: Global averages could also be driven up by about 0.75C if pollution from industry is rapidly cleaned up. This unexpected result occurs because tiny specks from industrial activity block solar radiation from reaching the ground.

Preparing for the Unthinkable

The worst-case scenarios could be utilized in planning the construction of major projects, for example housing developments, nuclear power stations and water management networks. Understanding these environmental threats could also accelerate the push to slash fossil fuel emissions.

The study developed the extreme models using a mix of observed and historical experience, climate models and established principles. The scenarios exclude broader worldwide issues including the agricultural collapse and resource wars.

This work was requested as part of a official risk assessment framework. Independent analyses have warned that insufficient focus was being paid to low‐likelihood but high‐impact risks.

The government's climate advisors has stated that the UK needs to "adapt to 2C" and assess the threats for severe warming. Past policy documents have been labeled being "very weak" by some observers.

An official statement said: "The climate emergency is at the heart of the country's focus, both building resilience and establishing itself as a clean energy superpower. It is essential that the UK is prepared for the impacts."