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The direst projected effects of the climate crisis for the UK have been detailed by scientists, including a scorching 4C increase in mean temperatures to a 6.5-foot rise in sea level. Another scenario predicts a drop of 6C in temperatures following the collapse of critical Atlantic Ocean currents, which would severely impact food production and energy demand.

Credible Extremes, Not Predictions

These consequences, certain ones are linked to climate tipping points, are viewed as unlikely but possible. The team explained that these scenarios plugged a hole in planning that had rendered the UK not ready for catastrophic possibilities.

"The climate extremes we have detailed should not be seen as certainties, but they are possible," stated the professor who oversaw the study. "The nation has been formulating policy without the tools to assess extreme possibilities. We've now provided decision-makers what they need to get ready for environmental results they pray never occur, but must not overlook."

A Spectrum of Extreme Weather Possibilities

A second set of worst-case scenarios maps the possible scale of extreme weather between now and the year 2100. These indicate that thermometer readings could skyrocket in some months by up to 6C above average, while precipitation could be triple standard measurements.

The likelihood of the catastrophic events coming to pass could not be calculated due to uncertainty about what steps will be enacted to combat global warming and how the Earth's systems will respond. This research was likened to security threat evaluations or stress tests for the banking sector.

Key Outcome Details

• 4C Temperature Rise: Global temperatures exceeding 4C by 2100 could transpire if climate action fails or if vicious cycles including the Amazon rainforest becoming a net carbon source unleash its enormous store of carbon. This would lead to severe and lengthy heatwaves and water shortages plaguing the UK in summer.
• Ocean Circulation Failure: A major ocean current, the Atlantic meridional overturning circulation (Amoc), is losing strength and losing stability due to climate change. A full shutdown beginning in 2030 would lead to a 6C cooling in the UK. "Agriculture would struggle enormously and freshwater availability would be drastically changed," explained the professor.
• Accelerated Coastal Flooding: A surge of 2.0-2.2 metres around the UK by 2100 could take place if ice sheets in the polar regions disintegrate quickly, inundating low-lying areas. Differing from the other scenarios, this risk is already known by infrastructure experts.
• Clean Air Warming: Global averages could also be driven up by about 0.75C if airborne particulates is drastically reduced. This counterintuitive effect occurs because aerosol particles from fossil fuel combustion reflect sunlight from warming the ground.

Preparing for the Unthinkable

These dire projections could be applied to guide the building of long-term infrastructure, for example housing developments, energy plants and urban drainage systems. Understanding these future hazards could also accelerate the drive to slash greenhouse gas emissions.

The research developed the worst-case scenarios using a combination of observed and historical experience, climate models and scientific theory. These outcomes exclude international cascading effects including the devastation of food supplies and geopolitical instability.

The project was initiated as part of a national climate resilience programme. Previous assessments have stated that not enough attention was being paid to low‐likelihood but high‐impact risks.

The government's climate advisors has said that the UK needs to "become resilient to moderate heating" and assess the threats for four degrees. Previous adaptation plans have been labeled being "very weak" by some observers.

An official statement noted: "The climate emergency is at the core of this government’s agenda, both preparing for impacts and establishing itself as a low-carbon economy. It is vital that the UK is prepared for the effects."