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The most severe potential impacts of the climate crisis for the UK have been outlined by researchers, including a searing 4C increase in temperatures to a 6.5-foot increase in sea level. A separate possibility envisions a drop of 6C in temperatures following the shutdown of key Atlantic Ocean currents, which would severely impact food production and energy needs.

Credible Extremes, Not Guarantees

These effects, a number of which are linked to climate tipping points, are considered as unlikely but possible. The team explained that these models addressed a shortfall in risk assessment that had rendered the UK unprepared for extreme outcomes.

"The severe weather events we have mapped should not be seen as certainties, but they are plausible," stated Nigel Arnell who led the research. "The nation has been making preparations in the absence of the methods to plan for worst-case scenarios. We've now given planners what they need to get ready for future conditions they pray never occur, but must not overlook."

A Spectrum of Severe Conditions Scenarios

Another collection of dire projections sets out the potential extent of extreme weather between now and the close of the 2100s. These indicate that temperatures could soar in particular seasons by up to 6C higher than the norm, while precipitation could be triple typical amounts.

The probability of the worst-case outcomes happening cannot be precisely determined due to a lack of certainty about what measures will be enacted to tackle global warming and how the climate system will react. This research was described as similar to security threat evaluations or resilience checks for the banking sector.

Critical Possibility Details

• Severe Heating: Planetary heating exceeding 4C by 2100 could happen if international cooperation collapses or if powerful amplifying effects including the tropical forests perishing unleash its enormous store of carbon. This would cause severe and lengthy heat domes and water shortages affecting the UK in summer.
• Atlantic Current Collapse: A critical sea current, the AMOC, is losing strength and losing stability due to ocean warming. A complete failure beginning in 2030 would lead to a drastic cooling in the UK. "Agriculture would face immense difficulties and freshwater availability would be fundamentally reshaped," said the lead researcher.
• Rapid Sea Level Rise: A rise of 2.0-2.2 metres around the UK by 2100 could take place if polar ice in Greenland and Antarctica disintegrate quickly, inundating seaside communities. Unlike the other scenarios, this threat is already known by planners.
• Aerosol Effect: Temperatures could also be increased by about 0.75C if pollution from industry is sharply cut. This counterintuitive effect occurs because tiny specks from burning coal block solar radiation from warming the ground.

Planning for the Unthinkable

The worst-case scenarios could be applied to guide the construction of major projects, such as expanded cities, nuclear power stations and urban drainage systems. Awareness of these environmental threats could also accelerate the push to slash greenhouse gas emissions.

The analysis formulated the extreme models using a mix of past data and records, computer simulations and climate physics. These outcomes do not take into account international cascading effects including the devastation of food supplies and increased conflict.

The project was initiated as part of a official climate resilience programme. Previous assessments have stated that insufficient focus was being given to high-consequence, low-probability risks.

An independent advisory body has stated that the UK needs to "become resilient to moderate heating" and evaluate the threats for 4C. Earlier government strategies have been described as being "insufficient" by some observers.

A national response said: "The climate emergency is at the center 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 effects."