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The direst potential impacts of the climate crisis for the UK have been mapped by researchers, ranging from a blistering 4C increase in temperatures to a two-metre surge in sea levels. Another scenario foresees a plunge of 6C in temperature following the failure of key Atlantic Ocean currents, which would massively disrupt food production and energy needs.

Plausible Events, Not Predictions

These impacts, a number of which are associated with critical climate thresholds, are considered as unlikely but plausible. The researchers said that these scenarios plugged a hole in risk assessment that had rendered the UK not ready for extreme outcomes.

"The climate extremes we have detailed are not forecasts, but they are possible," stated the professor who directed the study. "The UK has been planning lacking the frameworks to assess catastrophic outcomes. We've now supplied planners what they need to prepare for future conditions they pray never occur, but must not overlook."

A Suite of Severe Conditions Possibilities

A further series of dire projections maps the possible scale of harsh climate between now and the year 2100. These indicate that temperatures could skyrocket in certain periods by up to 6C higher than average, while rainfall could be three times typical amounts.

The chance of the extreme scenarios occurring could not be calculated due to unknown factors about what measures will be enacted to address global warming and how the Earth's systems will react. This approach was likened to defence planning or scenario planning for financial systems.

Critical Scenario Highlights

• Severe Heating: Planetary heating exceeding 4C by 2100 could happen if emissions cuts breaks down or if strong feedback loops like the tropical forests dying unleash its enormous store of carbon. This would cause extreme and prolonged heat domes and droughts plaguing the UK in summer.
• AMOC Shutdown: A critical sea current, the AMOC, is weakening and losing stability due to ocean warming. A full shutdown starting around 2030 would lead to a drastic cooling in the UK. "Crop production would struggle enormously and freshwater availability would be completely altered," said the professor.
• Accelerated Coastal Flooding: A increase of 2.0-2.2 metres around the UK by 2100 could happen if glaciers in the polar regions collapse rapidly, submerging low-lying areas. Differing from the other scenarios, this threat is already recognized by infrastructure experts.
• Aerosol Effect: Temperatures could also be pushed higher by about 0.75C if airborne particulates is rapidly cleaned up. This paradoxical outcome occurs because tiny specks from fossil fuel combustion reflect solar radiation from reaching the ground.

Preparing for the Extreme

The severe models could be used to inform the building of critical national infrastructure, for example expanded cities, energy plants and water management networks. Knowledge about these climate risks could also speed the push to slash carbon pollution.

The analysis formulated the worst-case scenarios using a combination of observed and historical experience, computer simulations and climate physics. The scenarios exclude international cascading effects including the global food shortages and resource wars.

The research was requested as part of a official risk assessment framework. Independent analyses have warned that insufficient focus was being given to low‐likelihood but high‐impact risks.

An independent advisory body has said that the UK must "become resilient to moderate heating" and examine the risks for four degrees. Earlier government strategies have been criticised as being "very weak" by some observers.

An official statement noted: "Global warming is at the heart of our national priorities, both building resilience and transitioning to a renewable energy leader. It is essential that the UK is ready for the effects."