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The most severe potential impacts of the global heating for the UK have been outlined by scientists, ranging from a blistering 4C jump in average temperatures to a 6.5-foot surge in sea level. Another scenario predicts a drop of 6C in temperature following the failure of key Atlantic Ocean currents, which would profoundly upset agriculture and energy needs.

Plausible Outcomes, Not Guarantees

These effects, some of which are connected to critical climate thresholds, are viewed as improbable but plausible. The scientists said that these projections filled a gap in planning that had left the UK not ready for worst-case results.

"The severe weather events we have outlined should not be seen as certainties, but they are plausible," stated the lead researcher who led the research. "The UK has been making preparations in the absence of the frameworks to plan for extreme possibilities. We've now supplied decision-makers what they need to get ready for future conditions they hope never happen, but can’t afford to ignore."

A Range of Extreme Weather Scenarios

Another collection of severe models details the potential extent of severe conditions between now and the close of the 2100s. These indicate that temperatures could rocket in some months by up to 6C above the norm, while rainfall could be 300% of normal levels.

The probability of the catastrophic events happening could not be calculated due to unknown factors about what measures will be enacted to combat global warming and how the planet's climate will respond. This research was described as similar to national security risk assessments or stress tests for the banking sector.

Critical Outcome Details

• Severe Heating: Planetary heating soaring past 4C by 2100 could transpire if international cooperation breaks down or if vicious cycles like the Amazon rainforest becoming a net carbon source emit its huge repository of carbon. This would lead to intense and enduring heat domes and droughts affecting the UK in summer.
• Ocean Circulation Failure: A key circulation system, the Atlantic meridional overturning circulation (Amoc), is slowing down and becoming unstable due to climate change. A complete failure commencing by 2030 would lead to a six-degree temperature drop in the UK. "Farming would be severely challenged and water resources would be drastically changed," 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 glaciers in Greenland and Antarctica disintegrate quickly, flooding low-lying areas. Unlike the other scenarios, this risk is already recognized by planners.
• Pollution Paradox: Global averages could also be driven up by about 0.75C if airborne particulates is drastically reduced. This unexpected result occurs because aerosol particles from burning coal block solar radiation from warming the ground.

Planning for the Extreme

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 accelerate the drive to reduce fossil fuel emissions.

The analysis formulated the worst-case scenarios using a mix of past data and records, climate models and climate physics. The scenarios exclude international cascading effects including the agricultural collapse and resource wars.

The project was initiated as part of a government’s adaptation planning initiative. Previous assessments have stated that too little consideration was being allocated to low‐likelihood but high‐impact risks.

The government's climate advisors has recommended that the UK must "prepare for two degrees of warming" and evaluate the threats for four degrees. Previous adaptation plans have been criticised as being "very weak" by environmental groups.

A government spokesperson said: "The climate emergency is at the heart of this government’s agenda, both preparing for impacts and establishing itself as a clean energy superpower. It is crucial that the UK is resilient for the impacts."