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The most severe projected effects of the climate crisis for the UK have been mapped by experts, ranging from a blistering 4C jump in temperatures to a two-metre surge in sea levels. A separate possibility foresees a decline of 6C in temperatures following the collapse of critical Atlantic Ocean currents, which would massively disrupt food production and power requirements.

Possible Outcomes, Not Predictions

These effects, a number of which are connected to climate tipping points, are considered as unlikely but plausible. The scientists explained that these models filled a gap in risk assessment that had rendered the UK ill-prepared for catastrophic possibilities.

"The severe weather events we have outlined should not be seen as certainties, but they are possible," commented the lead researcher who directed the study. "The UK has been formulating policy in the absence of the frameworks to plan for worst-case scenarios. We've now supplied planners what they need to plan for future conditions they wish to avoid, but dare not dismiss."

A Spectrum of Severe Conditions Scenarios

A further series of severe models sets out the possible scale of extreme weather between now and the close of the 2100s. These suggest that thermometer readings could soar in certain periods by up to 6C above average, while precipitation could be three times standard measurements.

The likelihood of the extreme scenarios coming to pass could not be calculated due to uncertainty about what steps will be taken to tackle global heating and how the Earth's systems will react. This approach was described as similar to security threat evaluations or scenario planning for the banking sector.

Key Scenario Details

• 4C Temperature Rise: Global temperatures rising well above 4C by 2100 could transpire if climate action breaks down or if vicious cycles such as the Amazon basin dying unleash its huge repository of carbon. This would result in severe and lengthy heatwaves and dry spells plaguing the UK in summer.
• Ocean Circulation Failure: A major ocean current, the North Atlantic current, is slowing down and losing stability due to ocean warming. A collapse starting around 2030 would lead to a 6C cooling in the UK. "Farming would be severely challenged and water resources would be completely altered," said Arnell.
• Rapid Sea Level Rise: A surge of 2.0-2.2 metres around the UK by 2100 could take place if polar ice in the polar regions disintegrate quickly, submerging low-lying areas. In contrast to the other scenarios, this possibility is already known by coastal engineers.
• Clean Air Warming: Global averages could also be driven up by about 0.75C if airborne particulates is sharply cut. This paradoxical outcome occurs because aerosol particles from industrial activity block sunlight from reaching the ground.

Preparing for the Worst

The severe models could be used to inform the building of major projects, for example expanded cities, nuclear power stations and urban drainage systems. Awareness of these environmental threats could also accelerate the transition to slash greenhouse gas emissions.

The study developed the worst-case scenarios using a combination of real-world events, digital projections and scientific theory. The possibilities exclude broader worldwide issues like the agricultural collapse and resource wars.

The project was commissioned as part of a official climate resilience programme. Earlier reports have stated that insufficient focus was being paid to catastrophic yet improbable risks.

An independent advisory body has said that the UK must "become resilient to moderate heating" and assess the risks for severe warming. Past policy documents have been described as being "very weak" by certain experts.

An official statement commented: "The climate emergency is at the core of this government’s agenda, both building resilience and becoming a renewable energy leader. It is essential that the UK is prepared for the effects."