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The most severe possible consequences of the climate emergency for the UK have been detailed by researchers, ranging from a blistering 4C increase in mean temperatures to a 2-metre increase in sea levels. A separate possibility foresees a drop of 6C in temperature following the shutdown of key Atlantic Ocean currents, which would profoundly upset farming and energy demand.

Possible Outcomes, Not Forecasts

These consequences, certain ones are linked to irreversible climate shifts, are considered as low probability but credible. The researchers said that these scenarios addressed a shortfall in planning that had rendered the UK unprepared for worst-case results.

"The severe weather events we have outlined aren’t predictions, but they are plausible," stated the lead researcher who led the analysis. "Britain has been making preparations lacking the tools to test against extreme possibilities. We've now given decision-makers what they need to prepare for environmental results they hope never happen, but dare not dismiss."

A Range of Harsh Climate Scenarios

A second set of severe models maps the possible scale of extreme weather between now and the close of the 2100s. These indicate that temperatures could skyrocket in certain periods by up to 6C above average, while rainfall could be three times standard measurements.

The likelihood of the catastrophic events occurring could not be calculated due to uncertainty about what measures will be taken to combat global heating and how the climate system will behave. This analysis was described as similar to security threat evaluations or stress tests for economic stability.

Critical Scenario Details

• Severe Heating: Worldwide averages rising well above 4C by 2100 could transpire if emissions cuts collapses or if strong feedback loops such as the Amazon basin perishing release its enormous store of carbon. This would lead to extreme and prolonged heat domes and dry spells hitting the UK in summer.
• AMOC Shutdown: A key circulation system, the North Atlantic current, is weakening and showing signs of collapse due to ocean warming. A full shutdown starting around 2030 would lead to a six-degree temperature drop in the UK. "Agriculture would face immense difficulties and freshwater availability would be completely altered," noted Arnell.
• Rapid Sea Level Rise: A rise of 2.0-2.2 metres around the UK by 2100 could happen if polar ice in Greenland and Antarctica collapse rapidly, flooding seaside communities. Differing from the other scenarios, this possibility is already known by infrastructure experts.
• Aerosol Effect: Temperatures could also be pushed higher by about 0.75C if pollution from industry is sharply cut. This unexpected result occurs because tiny specks from industrial activity block sunlight from reaching the ground.

Planning for the Unthinkable

These dire projections could be utilized in planning the development of critical national infrastructure, for example new towns, energy plants and flood defences. Understanding these environmental threats could also speed the push to reduce carbon pollution.

The study created the severe projections using a mix of past data and records, computer simulations and climate physics. The scenarios omit potential global problems including the agricultural collapse and geopolitical instability.

The project was initiated as part of a national risk assessment framework. Independent analyses have cautioned that insufficient focus was being given to low‐likelihood but high‐impact risks.

An independent advisory body has recommended that the UK needs to "adapt to 2C" and examine the dangers for severe warming. Past policy documents have been criticised as being "insufficient" by certain experts.

An official statement noted: "The climate emergency is at the heart of the country's focus, both building resilience and transitioning to a clean energy superpower. It is vital that the UK is prepared for the consequences."