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The gravest projected effects of the climate crisis for the UK have been detailed by researchers, ranging from a blistering 4C increase in average temperatures to a 6.5-foot rise in sea level. Another scenario predicts a plunge of 6C in temperatures following the collapse of key Atlantic Ocean currents, which would massively disrupt farming and power requirements.

Possible Events, Not Guarantees

These consequences, certain ones are connected to irreversible climate shifts, are considered as unlikely but possible. The scientists said that these projections filled a gap in forecasting that had left the UK ill-prepared for extreme outcomes.

"The climate extremes we have outlined are not forecasts, but they are possible," said the lead researcher who oversaw the research. "Britain has been making preparations lacking the frameworks to plan for extreme possibilities. We've now given planners what they need to plan for future conditions they pray never occur, but can’t afford to ignore."

A Range of Extreme Weather Projections

Another collection of worst-case scenarios sets out the projected severity of extreme weather between now and the end of the century. These show that temperatures could rocket in particular seasons by up to 6C higher than average, while precipitation could be three times typical amounts.

The likelihood of the extreme scenarios occurring remains uncertain due to a lack of certainty about what steps will be implemented to tackle global warming and how the planet's climate will behave. This research was described as similar to national security risk assessments or resilience checks for financial systems.

Major Outcome Details

• 4C Temperature Rise: Global temperatures exceeding 4C by 2100 could transpire if emissions cuts fails or if strong feedback loops like the Amazon basin becoming a net carbon source release its vast reserves of carbon. This would lead to intense and enduring heat domes and droughts affecting the UK in summer.
• Atlantic Current Collapse: A major ocean current, the AMOC, is losing strength and losing stability due to ocean warming. A full shutdown starting around 2030 would lead to a six-degree temperature drop in the UK. "Agriculture would struggle enormously and water supplies would be drastically changed," explained the lead researcher.
• Accelerated Coastal Flooding: A surge of 2.0-2.2 metres around the UK by 2100 could occur if polar ice in the polar regions disintegrate quickly, flooding low-lying areas. Differing from the other scenarios, this risk is already understood by planners.
• Clean Air Warming: Temperatures could also be increased by about 0.75C if pollution from industry is rapidly cleaned up. This unexpected result occurs because pollution particles from industrial activity block sunlight from warming the ground.

Preparing for the Worst

The worst-case scenarios could be used to inform the construction of major projects, for example expanded cities, nuclear power stations and urban drainage systems. Understanding these environmental threats could also hasten the transition to slash carbon pollution.

The research created the extreme models using a combination of observed and historical experience, climate models and climate physics. The possibilities exclude broader worldwide issues such as the agricultural collapse and geopolitical instability.

The project was requested as part of a official risk assessment framework. Previous assessments have stated that insufficient focus was being given to high-consequence, low-probability risks.

An independent advisory body has said that the UK needs to "adapt to 2C" and assess the dangers for four degrees. Previous adaptation plans have been criticised as being "very weak" by environmental groups.

A national response commented: "Climate change is at the heart of this government’s agenda, both building resilience and becoming a low-carbon economy. It is essential that the UK is ready for the effects."