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The direst possible consequences of the global heating for the UK have been outlined by scientists, including a scorching 4C increase in temperatures to a two-metre surge in sea level. Another scenario envisions a drop of 6C in temperature following the shutdown of key Atlantic Ocean currents, which would profoundly upset farming and power requirements.

Plausible Events, Not Guarantees

These impacts, a number of which are linked to critical climate thresholds, are seen as unlikely but credible. The researchers stated that these models plugged a hole in forecasting that had rendered the UK unprepared for extreme outcomes.

"The severe weather events we have outlined should not be seen as certainties, but they are credible," said the professor who directed the analysis. "The UK has been formulating policy without the tools to assess worst-case scenarios. We've now given planners what they need to prepare for climate outcomes they pray never occur, but can’t afford to ignore."

A Range of Harsh Climate Projections

Another collection of dire projections maps the projected severity of extreme weather between now and the year 2100. These indicate that thermometer readings could skyrocket in particular seasons by up to 6C above average, while precipitation could be three times typical amounts.

The probability of the worst-case outcomes happening remains uncertain due to a lack of certainty about what action will be implemented to combat global warming and how the climate system will react. This approach was compared to security threat evaluations or scenario planning for the banking sector.

Major Possibility Elements

• Severe Heating: Planetary heating exceeding 4C by 2100 could happen if emissions cuts breaks down or if strong feedback loops such as the Amazon basin becoming a net carbon source release its enormous store of carbon. This would cause extreme and prolonged heat domes and droughts hitting the UK in summer.
• AMOC Shutdown: A major ocean current, the Atlantic meridional overturning circulation (Amoc), is losing strength and showing signs of collapse due to global heating. A collapse commencing by 2030 would lead to a drastic cooling in the UK. "Agriculture would face immense difficulties and water resources would be fundamentally reshaped," said Arnell.
• Rapid Sea Level Rise: A surge of 2.0-2.2 metres around the UK by 2100 could happen if glaciers in the Arctic and Antarctic disintegrate quickly, inundating low-lying areas. In contrast to the other scenarios, this threat is already understood by planners.
• Pollution Paradox: Temperatures could also be increased by about 0.75C if airborne particulates is drastically reduced. This counterintuitive effect occurs because pollution particles from fossil fuel combustion scatter solar radiation from warming the ground.

Planning for the Extreme

The worst-case scenarios could be used to inform the development of critical national infrastructure, such as expanded cities, nuclear power stations and urban drainage systems. Knowledge about these environmental threats could also speed the drive to reduce carbon pollution.

The research developed the extreme models using a combination of past data and records, digital projections and established principles. These outcomes exclude potential global problems like the agricultural collapse and geopolitical instability.

The project was initiated as part of a national risk assessment framework. Earlier reports have stated that too little consideration was being given to high-consequence, low-probability risks.

Official experts has said that the UK must "adapt to 2C" and evaluate the threats for severe warming. Previous adaptation plans have been described as being "inadequate" by certain experts.

A national response commented: "Global warming is at the center of the country's focus, both building resilience and transitioning to a renewable energy leader. It is vital that the UK is resilient for the effects."