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The direst potential impacts of the global heating for the UK have been mapped by experts, encompassing a scorching 4C increase in temperatures to a 2-metre rise in sea levels. An alternative projection predicts a plunge of 6C in temperatures following the collapse of crucial Atlantic Ocean currents, which would massively disrupt food production and power requirements.

Credible Extremes, Not Forecasts

These effects, some of which are connected to climate tipping points, are viewed as unlikely but credible. The team explained that these scenarios plugged a hole in risk assessment that had rendered the UK unprepared for worst-case results.

"The worst-case scenarios we have outlined are not forecasts, but they are credible," commented the professor who oversaw the analysis. "The UK has been formulating policy in the absence of the tools to test against worst-case scenarios. We've now supplied policymakers what they need to get ready for environmental results they hope never happen, but can’t afford to ignore."

A Suite of Severe Conditions Projections

A second set of severe models details the possible scale of extreme weather between now and the close of the 2100s. These suggest that temperatures could skyrocket in particular seasons by up to 6C higher than historical levels, while rainfall could be three times standard measurements.

The probability of the extreme scenarios occurring remains uncertain due to unknown factors about what steps will be enacted to tackle climate change and how the planet's climate will react. This research was described as similar to security threat evaluations or stress tests for the banking sector.

Major Outcome Details

• 4C Temperature Rise: Planetary heating soaring past 4C by 2100 could transpire if international cooperation breaks down or if powerful amplifying effects like the Amazon basin becoming a net carbon source release its huge repository of carbon. This would cause intense and enduring heatwaves and droughts affecting the UK in summer.
• AMOC Shutdown: A critical sea current, the North Atlantic current, is losing strength and losing stability due to ocean warming. A full shutdown starting around 2030 would lead to a 6C cooling in the UK. "Agriculture would struggle enormously and freshwater availability would be completely altered," noted the lead researcher.
• Sudden Ocean Inundation: A surge of 2.0-2.2 metres around the UK by 2100 could occur if glaciers in Greenland and Antarctica collapse rapidly, inundating low-lying areas. Differing from the other scenarios, this risk is already understood by infrastructure experts.
• Clean Air Warming: Temperatures could also be driven up by about 0.75C if airborne particulates is rapidly cleaned up. This paradoxical outcome occurs because aerosol particles from fossil fuel combustion scatter sunlight from warming the ground.

Building Resilience Against the Extreme

The severe models could be used to inform the building of major projects, including new towns, nuclear power stations and water management networks. Awareness of these climate risks could also accelerate the drive to cut greenhouse gas emissions.

The analysis formulated the severe projections using a blend of observed and historical experience, computer simulations and scientific theory. These outcomes exclude international cascading effects like the global food shortages and increased conflict.

The research was requested as part of a government’s adaptation planning initiative. Previous assessments have stated that not enough attention was being given to catastrophic yet improbable risks.

An independent advisory body has recommended that the UK must "become resilient to moderate heating" and examine the dangers for severe warming. Past policy documents have been labeled being "inadequate" by environmental groups.

An official statement commented: "Global warming is at the center of the country's focus, both adapting for the future and transitioning to a clean energy superpower. It is essential that the UK is prepared for the consequences."