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The direst possible consequences of the global heating for the UK have been outlined by experts, encompassing a blistering 4C rise in mean temperatures to a 2-metre surge in sea levels. A separate possibility foresees a drop of 6C in temperatures following the collapse of critical Atlantic Ocean currents, which would massively disrupt agriculture and energy needs.

Possible Outcomes, Not Forecasts

These consequences, some of which are associated with irreversible climate shifts, are seen as unlikely but plausible. The scientists stated that these models filled a gap in planning that had left the UK not ready for extreme outcomes.

"The climate extremes we have detailed aren’t predictions, but they are plausible," stated the lead researcher who directed the research. "The nation has been making preparations in the absence of the frameworks to assess catastrophic outcomes. We've now provided policymakers what they need to plan for climate outcomes they pray never occur, but must not overlook."

A Range of Severe Conditions Scenarios

A second set of dire projections maps the possible scale of severe conditions between now and the end of the century. These indicate that thermometer readings could rocket in certain periods by up to 6C above average, while precipitation could be triple standard measurements.

The probability of the worst-case outcomes happening remains uncertain due to uncertainty about what steps will be implemented to tackle global warming and how the planet's climate will react. This approach was described as similar to security threat evaluations or scenario planning for the banking sector.

Major Scenario Elements

• 4C Temperature Rise: Planetary heating rising well above 4C by 2100 could happen if emissions cuts breaks down or if strong feedback loops including the Amazon basin perishing emit its vast reserves of carbon. This would lead to intense and enduring heatwaves and water shortages hitting the UK in summer.
• Ocean Circulation Failure: A critical sea current, the Atlantic meridional overturning circulation (Amoc), is slowing down and losing stability due to global heating. A full shutdown commencing by 2030 would lead to a 6C cooling in the UK. "Farming would be severely challenged and water resources would be fundamentally reshaped," noted the professor.
• Rapid Sea Level Rise: A increase of 2.0-2.2 metres around the UK by 2100 could occur if glaciers in Greenland and Antarctica disintegrate quickly, inundating low-lying areas. In contrast to the other scenarios, this possibility is already known by planners.
• Aerosol Effect: Global averages could also be increased by about 0.75C if airborne particulates is drastically reduced. This counterintuitive effect occurs because aerosol particles from burning coal reflect sunlight from reaching the ground.

Planning for the Unthinkable

The worst-case scenarios could be utilized in planning the construction of major projects, including housing developments, energy plants and urban drainage systems. Knowledge about these climate risks could also speed the transition to slash carbon pollution.

The research developed the extreme models using a combination of past data and records, digital projections and established principles. The scenarios exclude potential global problems like the global food shortages and resource wars.

The research was initiated as part of a government’s adaptation planning initiative. Previous assessments have warned that insufficient focus was being allocated to low‐likelihood but high‐impact risks.

Official experts has stated that the UK needs to "adapt to 2C" and assess the dangers for severe warming. Past policy documents have been criticised as being "insufficient" by certain experts.

A government spokesperson said: "Climate change is at the core of our national priorities, both adapting for the future and becoming a renewable energy leader. It is essential that the UK is resilient for the impacts."