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The gravest possible consequences of the climate crisis for the UK have been outlined by scientists, encompassing a scorching 4C jump in temperatures to a two-metre increase in ocean levels. Another scenario envisions a decline of 6C in temperature following the shutdown of critical Atlantic Ocean currents, which would profoundly upset farming and energy needs.

Plausible Extremes, Not Predictions

These impacts, a number of which are connected to climate tipping points, are seen as improbable but possible. The team explained that these models addressed a shortfall in forecasting that had rendered the UK unprepared for catastrophic possibilities.

"The severe weather events we have detailed aren’t predictions, but they are credible," said the lead researcher who oversaw the analysis. "The nation has been planning without the methods to plan for extreme possibilities. We've now provided planners what they need to get ready for climate outcomes they hope never happen, but must not overlook."

A Suite of Extreme Weather Projections

A further series of severe models details the possible scale of extreme weather between now and the year 2100. These suggest that thermometer readings could soar in certain periods by up to 6C higher than historical levels, while precipitation could be three times normal levels.

The probability of the catastrophic events occurring cannot be precisely determined due to a lack of certainty about what measures will be taken to address climate change and how the climate system will respond. This approach was described as similar to defence planning or scenario planning for financial systems.

Critical Possibility Elements

• Severe Heating: Planetary heating exceeding 4C by 2100 could happen if emissions cuts fails or if powerful amplifying effects like the Amazon rainforest perishing emit its vast reserves of carbon. This would lead to extreme and prolonged heat domes and water shortages hitting the UK in summer.
• Atlantic Current Collapse: A major ocean current, the North Atlantic current, is weakening and losing stability due to ocean warming. A full shutdown commencing by 2030 would lead to a six-degree temperature drop in the UK. "Agriculture would struggle enormously and freshwater availability would be drastically changed," noted the lead researcher.
• Accelerated Coastal Flooding: A increase of 2.0-2.2 metres around the UK by 2100 could happen if polar ice in Greenland and Antarctica collapse rapidly, submerging seaside communities. Differing from the other scenarios, this risk is already understood by infrastructure experts.
• Pollution Paradox: Global averages could also be driven up by about 0.75C if pollution from industry is rapidly cleaned up. This unexpected result occurs because aerosol particles from industrial activity scatter sunlight from reaching the ground.

Preparing for the Unthinkable

These dire projections could be used to inform the development of critical national infrastructure, such as new towns, power generation facilities and urban drainage systems. Understanding these environmental threats could also speed the push to reduce carbon pollution.

The study created the worst-case scenarios using a mix of real-world events, climate models and established principles. The scenarios exclude potential global problems such as the agricultural collapse and resource wars.

This work was commissioned as part of a official risk assessment framework. Previous assessments have cautioned that not enough attention was being paid to low‐likelihood but high‐impact risks.

Official experts has said that the UK needs to "prepare for two degrees of warming" and examine the risks for 4C. Earlier government strategies have been criticised as being "inadequate" by environmental groups.

An official statement commented: "Climate change is at the heart of this government’s agenda, both preparing for impacts and transitioning to a clean energy superpower. It is vital that the UK is resilient for the consequences."