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The direst projected effects of the global heating for the UK have been detailed by scientists, including a searing 4C jump in temperatures to a 2-metre surge in ocean levels. An alternative projection envisions a drop of 6C in temperature following the shutdown of critical Atlantic Ocean currents, which would profoundly upset agriculture and power requirements.

Credible Extremes, Not Predictions

These consequences, certain ones are associated with climate tipping points, are viewed as low probability but plausible. The team explained that these projections addressed a shortfall in risk assessment that had left the UK unprepared for catastrophic possibilities.

"The climate extremes we have mapped should not be seen as certainties, but they are plausible," stated Nigel Arnell who oversaw the research. "The UK has been formulating policy in the absence of the frameworks to test against worst-case scenarios. We've now given planners what they need to prepare for environmental results they hope never happen, but dare not dismiss."

A Range of Severe Conditions Projections

A second set of severe models maps the possible scale of extreme weather between now and the year 2100. These indicate that temperatures could rocket in particular seasons by up to 6C above historical levels, while rainfall could be 300% of typical amounts.

The likelihood of the catastrophic events occurring remains uncertain due to unknown factors about what measures will be implemented to address global warming and how the Earth's systems will behave. This research was described as similar to defence planning or scenario planning for economic stability.

Critical Outcome Elements

• 4C Temperature Rise: Global temperatures rising well above 4C by 2100 could occur if emissions cuts fails or if powerful amplifying effects including the Amazon basin dying release its huge repository of carbon. This would result in extreme and prolonged heat domes and dry spells hitting the UK in summer.
• Atlantic Current Collapse: A major ocean current, the AMOC, is losing strength and showing signs of collapse due to ocean warming. A full shutdown commencing by 2030 would lead to a drastic cooling in the UK. "Crop production would be severely challenged and freshwater availability would be drastically changed," noted the lead researcher.
• Rapid Sea Level Rise: A increase of 2.0-2.2 metres around the UK by 2100 could take place if polar ice in the polar regions disintegrate quickly, submerging coastal cities and towns. Unlike the other scenarios, this threat is already known by coastal engineers.
• Aerosol Effect: Temperatures could also be increased by about 0.75C if industrial aerosols is drastically reduced. This counterintuitive effect occurs because pollution particles from fossil fuel combustion scatter solar radiation from reaching the ground.

Preparing for the Unthinkable

These dire projections could be used to inform the construction of long-term infrastructure, for example housing developments, nuclear power stations and water management networks. Understanding these future hazards could also accelerate the drive to slash fossil fuel emissions.

The analysis developed the severe projections using a combination of observed and historical experience, digital projections and scientific theory. The possibilities exclude broader worldwide issues including the agricultural collapse and increased conflict.

This work was requested as part of a official risk assessment framework. Previous assessments have stated that too little consideration was being paid to catastrophic yet improbable risks.

An independent advisory body has recommended that the UK needs to "prepare for two degrees of warming" and examine the threats for 4C. Earlier government strategies have been criticised as being "very weak" by some observers.

An official statement commented: "The climate emergency is at the core of our national priorities, both building resilience and becoming a clean energy superpower. It is essential that the UK is ready for the consequences."