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The direst potential impacts of the global heating for the UK have been outlined by experts, including a blistering 4C jump in temperatures to a 6.5-foot surge in sea level. A separate possibility envisions a plunge of 6C in temperature following the failure of crucial Atlantic Ocean currents, which would massively disrupt farming and power requirements.

Plausible Extremes, Not Guarantees

These consequences, some of which are connected to critical climate thresholds, are viewed as low probability but possible. The researchers said that these models addressed a shortfall in planning that had left the UK not ready for extreme outcomes.

"The climate extremes we have outlined should not be seen as certainties, but they are plausible," said Nigel Arnell who directed the study. "The UK has been making preparations without the frameworks to assess extreme possibilities. We've now provided decision-makers what they need to get ready for environmental results they wish to avoid, but can’t afford to ignore."

A Range of Harsh Climate Possibilities

A second set of dire projections details the potential extent of extreme weather between now and the year 2100. These suggest that thermometer readings could soar in certain periods by up to 6C above historical levels, while rainfall could be three times typical amounts.

The probability of the catastrophic events happening remains uncertain due to a lack of certainty about what action will be enacted to address climate change and how the planet's climate will behave. This research was described as similar to security threat evaluations or stress tests for financial systems.

Major Scenario Elements

• Severe Heating: Global temperatures rising well above 4C by 2100 could transpire if climate action breaks down or if strong feedback loops including the tropical forests becoming a net carbon source release its enormous store of carbon. This would lead to extreme and prolonged heatwaves and water shortages plaguing the UK in summer.
• Atlantic Current Collapse: A major ocean current, the AMOC, is weakening and becoming unstable due to global heating. A collapse starting around 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," explained Arnell.
• Accelerated Coastal Flooding: A surge of 2.0-2.2 metres around the UK by 2100 could occur if polar ice in the Arctic and Antarctic collapse rapidly, submerging coastal cities and towns. Unlike the other scenarios, this threat is already known by planners.
• Aerosol Effect: Global averages could also be driven up by about 0.75C if industrial aerosols is drastically reduced. This unexpected result occurs because aerosol particles from industrial activity scatter solar radiation from reaching the ground.

Building Resilience Against the Unthinkable

The worst-case scenarios could be used to inform the development of long-term infrastructure, such as expanded cities, nuclear power stations and urban drainage systems. Understanding these climate risks could also hasten the transition to cut carbon pollution.

The research formulated the worst-case scenarios using a combination of past data and records, digital projections and climate physics. These outcomes omit broader worldwide issues including the global food shortages and increased conflict.

The project was commissioned as part of a national risk assessment framework. Earlier reports have warned that too little consideration was being given to catastrophic yet improbable risks.

Official experts has stated that the UK must "adapt to 2C" and assess the risks for severe warming. Past policy documents have been criticised as being "very weak" by environmental groups.

A government spokesperson noted: "Global warming is at the center of this government’s agenda, both building resilience and transitioning to a low-carbon economy. It is essential that the UK is prepared for the effects."