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The direst potential impacts of the climate crisis for the UK have been mapped by scientists, including a searing 4C rise in mean temperatures to a 2-metre increase in sea levels. An alternative projection foresees a plunge of 6C in temperatures following the failure of key Atlantic Ocean currents, which would severely impact food production and energy needs.

Credible Events, Not Guarantees

These effects, a number of which are associated with climate tipping points, are viewed as improbable but plausible. The researchers explained that these models addressed a shortfall in risk assessment that had left the UK unprepared for catastrophic possibilities.

"The climate extremes we have mapped are not forecasts, but they are possible," commented Nigel Arnell who oversaw the analysis. "Britain has been formulating policy in the absence of the tools to assess catastrophic outcomes. We've now supplied decision-makers what they need to get ready for environmental results they pray never occur, but must not overlook."

A Suite of Severe Conditions Projections

Another collection of dire projections details the possible scale of extreme weather between now and the end of the century. These show that thermometer readings could soar in certain periods by up to 6C above the norm, while precipitation could be 300% of typical amounts.

The chance of the extreme scenarios occurring could not be calculated due to uncertainty about what action will be enacted to combat global heating and how the climate system will react. This approach was likened to security threat evaluations or stress tests for economic stability.

Critical Possibility Details

• Severe Heating: Planetary heating rising well above 4C by 2100 could transpire if emissions cuts collapses or if powerful amplifying effects including the Amazon basin becoming a net carbon source emit its enormous store of carbon. This would cause extreme and prolonged heatwaves and dry spells hitting the UK in summer.
• Ocean Circulation Failure: A critical sea current, the Atlantic meridional overturning circulation (Amoc), is losing strength and losing stability due to ocean warming. 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 professor.
• 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 melt abruptly, submerging coastal cities and towns. Differing from the other scenarios, this risk is already recognized by planners.
• Pollution Paradox: Global averages could also be increased by about 0.75C if pollution from industry is rapidly cleaned up. This counterintuitive effect occurs because pollution particles from industrial activity scatter solar radiation from reaching the ground.

Building Resilience Against the Worst

The worst-case scenarios could be used to inform the development of critical national infrastructure, for example housing developments, power generation facilities and water management networks. Understanding these environmental threats could also hasten the drive to slash carbon pollution.

The research developed the extreme models using a blend of real-world events, digital projections and established principles. These outcomes do not take into account international cascading effects such as the global food shortages and increased conflict.

This work was initiated as part of a government’s adaptation planning initiative. Earlier reports have warned that insufficient focus was being allocated to catastrophic yet improbable risks.

An independent advisory body has stated that the UK needs to "prepare for two degrees of warming" and examine the threats for severe warming. Past policy documents have been criticised as being "inadequate" by certain experts.

An official statement noted: "Global warming is at the core of this government’s agenda, both preparing for impacts and transitioning to a low-carbon economy. It is essential that the UK is resilient for the impacts."