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The gravest projected effects of the climate crisis for the UK have been mapped by scientists, ranging from a blistering 4C jump in average temperatures to a 2-metre increase in ocean levels. Another scenario predicts a drop of 6C in temperature following the shutdown of crucial Atlantic Ocean currents, which would massively disrupt farming and energy demand.

Plausible Extremes, Not Predictions

These impacts, some of which are associated with critical climate thresholds, are seen as low probability but possible. The team stated that these models addressed a shortfall in planning that had rendered the UK unprepared for catastrophic possibilities.

"The worst-case scenarios we have mapped should not be seen as certainties, but they are credible," commented the professor who led the research. "The nation has been making preparations without the methods to test against extreme possibilities. We've now given policymakers what they need to prepare for climate outcomes they pray never occur, but must not overlook."

A Suite of Harsh Climate Projections

A further series of worst-case scenarios maps the potential extent of harsh climate between now and the year 2100. These suggest that thermometer readings could soar in some months by up to 6C higher than average, while rainfall could be three times standard measurements.

The probability of the extreme scenarios coming to pass could not be calculated due to uncertainty about what action will be enacted to address global heating and how the Earth's systems will respond. This research was compared to security threat evaluations or stress tests for economic stability.

Critical Outcome Elements

• 4C Temperature Rise: Worldwide averages soaring past 4C by 2100 could happen if international cooperation collapses or if strong feedback loops such as the tropical forests dying unleash its vast reserves of carbon. This would cause intense and enduring heat domes and dry spells affecting the UK in summer.
• AMOC Shutdown: A major ocean current, the North Atlantic current, is slowing down and becoming unstable due to ocean warming. A complete failure beginning in 2030 would lead to a 6C cooling in the UK. "Farming would be severely challenged and freshwater availability would be completely altered," explained the lead researcher.
• Rapid Sea Level Rise: A rise of 2.0-2.2 metres around the UK by 2100 could take place if polar ice in Greenland and Antarctica disintegrate quickly, submerging seaside communities. Unlike the other scenarios, this threat is already known by coastal engineers.
• Aerosol Effect: Global averages could also be pushed higher by about 0.75C if airborne particulates is drastically reduced. This counterintuitive effect occurs because pollution particles from fossil fuel combustion reflect solar radiation from warming the ground.

Building Resilience Against the Unthinkable

These dire projections could be used to inform the building of critical national infrastructure, for example housing developments, nuclear power stations and water management networks. Knowledge about these environmental threats could also accelerate the drive to cut carbon pollution.

The analysis created the severe projections using a mix of real-world events, digital projections and climate physics. These outcomes do not take into account international cascading effects such as the devastation of food supplies and increased conflict.

The project was requested as part of a official climate resilience programme. Independent analyses have warned that too little consideration was being given to high-consequence, low-probability risks.

Official experts has said that the UK needs to "prepare for two degrees of warming" and assess the risks for 4C. Previous adaptation plans have been labeled being "very weak" by certain experts.

An official statement said: "Climate change is at the heart of this government’s agenda, both adapting for the future and transitioning to a renewable energy leader. It is crucial that the UK is resilient for the consequences."