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The most severe possible consequences of the climate emergency for the UK have been outlined by researchers, ranging from a searing 4C increase in mean temperatures to a two-metre rise in ocean levels. A separate possibility foresees a decline of 6C in temperature following the collapse of key Atlantic Ocean currents, which would massively disrupt farming and energy demand.

Credible Events, Not Predictions

These impacts, a number of which are linked to climate tipping points, are viewed as low probability but plausible. The researchers stated that these models addressed a shortfall in planning that had rendered the UK ill-prepared for extreme outcomes.

"The climate extremes we have detailed should not be seen as certainties, but they are credible," said the lead researcher who led the study. "The nation has been planning in the absence of the tools to assess extreme possibilities. We've now provided planners what they need to plan for environmental results they hope never happen, but must not overlook."

A Suite of Harsh Climate Scenarios

Another collection of worst-case scenarios maps the projected severity of severe conditions between now and the close of the 2100s. These indicate that temperatures could skyrocket in particular seasons by up to 6C above average, while precipitation could be triple typical amounts.

The probability of the extreme scenarios occurring cannot be precisely determined due to unknown factors about what measures will be taken to combat global heating and how the climate system will react. This approach was described as similar to security threat evaluations or scenario planning for financial systems.

Major Scenario Elements

• Severe Heating: Planetary heating exceeding 4C by 2100 could occur if international cooperation fails or if powerful amplifying effects like the tropical forests perishing unleash its huge repository of carbon. This would lead to extreme and prolonged heat domes and droughts hitting the UK in summer.
• Atlantic Current Collapse: A major ocean current, the Atlantic meridional overturning circulation (Amoc), is weakening and showing signs of collapse due to ocean warming. A collapse starting around 2030 would lead to a drastic cooling in the UK. "Crop production would struggle enormously and water supplies 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 happen if ice sheets in the Arctic and Antarctic melt abruptly, submerging low-lying areas. In contrast to the other scenarios, this risk is already recognized by infrastructure experts.
• Aerosol Effect: Temperatures could also be increased by about 0.75C if airborne particulates is drastically reduced. This counterintuitive effect occurs because tiny specks from fossil fuel combustion scatter sunlight from reaching the ground.

Building Resilience Against the Extreme

The worst-case scenarios could be utilized in planning the building of critical national infrastructure, including expanded cities, power generation facilities and flood defences. Awareness of these climate risks could also hasten the transition to slash carbon pollution.

The study developed the extreme models using a blend of past data and records, digital projections and scientific theory. The scenarios exclude broader worldwide issues like the agricultural collapse and increased conflict.

The research was commissioned as part of a official climate resilience programme. Independent analyses have cautioned that not enough attention was being allocated to catastrophic yet improbable risks.

Official experts has recommended that the UK must "become resilient to moderate heating" and evaluate the risks for severe warming. Earlier government strategies have been criticised as being "insufficient" by some observers.

A national response commented: "Global warming is at the core of our national priorities, both preparing for impacts and establishing itself as a renewable energy leader. It is vital that the UK is prepared for the effects."