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The most severe potential impacts of the climate crisis for the UK have been mapped by researchers, ranging from a blistering 4C increase in temperatures to a two-metre rise in sea levels. Another scenario envisions a plunge of 6C in temperatures following the collapse of critical Atlantic Ocean currents, which would severely impact agriculture and power requirements.

Credible Events, Not Guarantees

These effects, some of which are connected to irreversible climate shifts, are viewed as improbable but credible. The researchers stated that these projections plugged a hole in risk assessment that had rendered the UK not ready for worst-case results.

"The severe weather events we have mapped aren’t predictions, but they are plausible," commented the professor who oversaw the research. "The nation has been making preparations without the tools to assess worst-case scenarios. We've now supplied policymakers what they need to plan for future conditions they wish to avoid, but can’t afford to ignore."

A Spectrum of Extreme Weather Scenarios

A second set of dire projections maps the possible scale of severe conditions between now and the year 2100. These suggest that thermometer readings could skyrocket in certain periods by up to 6C higher than the norm, while rainfall could be 300% of normal levels.

The chance of the extreme scenarios happening cannot be precisely determined due to a lack of certainty about what action will be enacted to tackle global warming and how the Earth's systems will respond. This approach was described as similar to defence planning or scenario planning for financial systems.

Critical Possibility Elements

• 4C Temperature Rise: Worldwide averages exceeding 4C by 2100 could occur if emissions cuts fails or if strong feedback loops like the Amazon rainforest dying emit its enormous store of carbon. This would lead to extreme and prolonged heat domes and dry spells hitting the UK in summer.
• Ocean Circulation Failure: A critical sea current, the Atlantic meridional overturning circulation (Amoc), is slowing down and losing stability due to climate change. A complete failure commencing by 2030 would lead to a six-degree temperature drop in the UK. "Crop production would be severely challenged and water supplies would be completely altered," noted the lead researcher.
• Accelerated Coastal Flooding: A increase of 2.0-2.2 metres around the UK by 2100 could occur if ice sheets in Greenland and Antarctica collapse rapidly, flooding low-lying areas. In contrast to the other scenarios, this threat is already known by infrastructure experts.
• Aerosol Effect: Global averages could also be pushed higher by about 0.75C if pollution from industry is rapidly cleaned up. This paradoxical outcome occurs because aerosol particles from burning coal scatter sunlight from reaching the ground.

Preparing for the Extreme

The worst-case scenarios could be applied to guide the construction of critical national infrastructure, for example new towns, nuclear power stations and urban drainage systems. Awareness of these future hazards could also hasten the transition to cut fossil fuel emissions.

The research created the extreme models using a mix of real-world events, computer simulations and scientific theory. The possibilities exclude potential global problems including the global food shortages and geopolitical instability.

The research was initiated as part of a national adaptation planning initiative. Independent analyses have cautioned that insufficient focus was being given to catastrophic yet improbable risks.

Official experts has stated that the UK must "adapt to 2C" and examine the threats for four degrees. Previous adaptation plans have been described as being "inadequate" by environmental groups.

An official statement noted: "The climate emergency is at the heart of this government’s agenda, both adapting for the future and becoming a low-carbon economy. It is crucial that the UK is prepared for the effects."