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The gravest projected effects of the climate crisis for the UK have been mapped by experts, encompassing a searing 4C jump in mean temperatures to a 6.5-foot increase in ocean levels. Another scenario predicts a drop of 6C in temperature following the failure of crucial Atlantic Ocean currents, which would severely impact farming and energy demand.

Possible Outcomes, Not Forecasts

These effects, some of which are associated with irreversible climate shifts, are considered as improbable but plausible. The researchers explained that these models addressed a shortfall in forecasting that had rendered the UK ill-prepared for extreme outcomes.

"The severe weather events we have mapped should not be seen as certainties, but they are possible," commented the lead researcher who directed the study. "Britain has been making preparations lacking the frameworks to assess extreme possibilities. We've now given planners what they need to plan for climate outcomes they hope never happen, but must not overlook."

A Suite of Extreme Weather Scenarios

A further series of dire projections maps the projected severity of severe conditions between now and the year 2100. These show that thermometer readings could rocket in particular seasons by up to 6C higher than average, while rainfall could be 300% of normal levels.

The likelihood of the extreme scenarios occurring could not be calculated due to uncertainty about what measures will be implemented to address global warming and how the planet's climate will respond. This research was described as similar to national security risk assessments or resilience checks for financial systems.

Critical Possibility Highlights

• Severe Heating: Planetary heating rising well above 4C by 2100 could occur if emissions cuts breaks down or if vicious cycles including the tropical forests dying emit its huge repository of carbon. This would lead to severe and lengthy heat domes and dry spells plaguing the UK in summer.
• AMOC Shutdown: A major ocean current, the North Atlantic current, is weakening and becoming unstable due to global heating. A complete failure commencing by 2030 would lead to a drastic cooling in the UK. "Farming would struggle enormously and freshwater availability would be completely altered," explained the professor.
• Accelerated Coastal Flooding: A surge of 2.0-2.2 metres around the UK by 2100 could take place if glaciers in Greenland and Antarctica disintegrate quickly, flooding low-lying areas. Differing from the other scenarios, this threat is already understood by planners.
• Clean Air Warming: Temperatures could also be driven up by about 0.75C if industrial aerosols is sharply cut. This unexpected result occurs because aerosol particles from fossil fuel combustion reflect sunlight from reaching the ground.

Building Resilience Against the Unthinkable

The worst-case scenarios could be used to inform the building of critical national infrastructure, for example housing developments, energy plants and flood defences. Knowledge about these future hazards could also hasten the drive to cut fossil fuel emissions.

The analysis formulated the severe projections using a blend of real-world events, climate models and climate physics. These outcomes do not take into account international cascading effects including the devastation of food supplies and resource wars.

This work was initiated as part of a official adaptation planning initiative. Previous assessments have stated that too little consideration was being given to low‐likelihood but high‐impact risks.

An independent advisory body has stated that the UK must "become resilient to moderate heating" and examine the threats for 4C. Past policy documents have been criticised as being "inadequate" by environmental groups.

An official statement commented: "Global warming is at the core of this government’s agenda, both building resilience and establishing itself as a low-carbon economy. It is essential that the UK is resilient for the consequences."