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The most severe potential impacts of the climate crisis for the UK have been outlined by experts, ranging from a blistering 4C increase in mean temperatures to a 6.5-foot increase in ocean levels. Another scenario predicts a decline of 6C in temperatures following the failure of critical Atlantic Ocean currents, which would profoundly upset agriculture and energy needs.

Credible Outcomes, Not Guarantees

These impacts, a number of which are linked to irreversible climate shifts, are seen as low probability but possible. The scientists explained that these scenarios plugged a hole in risk assessment that had left the UK ill-prepared for extreme outcomes.

"The climate extremes we have detailed should not be seen as certainties, but they are possible," stated the professor who led the research. "The nation has been planning without the frameworks to plan for worst-case scenarios. We've now provided planners what they need to prepare for climate outcomes they pray never occur, but can’t afford to ignore."

A Suite of Harsh Climate Projections

A further series of dire projections sets out the potential extent of harsh climate between now and the end of the century. These show that thermometer readings could rocket in some months by up to 6C above the norm, while precipitation could be triple normal levels.

The likelihood of the catastrophic events happening could not be calculated due to a lack of certainty about what action will be enacted to combat climate change and how the climate system will behave. This analysis was described as similar to defence planning or scenario planning for the banking sector.

Key Possibility Details

• Four-Degree Warming: Planetary heating soaring past 4C by 2100 could happen if emissions cuts collapses or if strong feedback loops including the Amazon basin perishing release its enormous store of carbon. This would lead to extreme and prolonged heat domes and water shortages hitting the UK in summer.
• Ocean Circulation Failure: A key circulation system, the AMOC, is slowing down and losing stability due to climate change. A complete failure commencing by 2030 would lead to a drastic cooling in the UK. "Farming would be severely challenged and freshwater availability would be drastically changed," said Arnell.
• Accelerated Coastal Flooding: A surge of 2.0-2.2 metres around the UK by 2100 could take place if ice sheets in the polar regions disintegrate quickly, flooding seaside communities. Differing from the other scenarios, this risk is already known by coastal engineers.
• Aerosol Effect: Temperatures could also be increased by about 0.75C if industrial aerosols is drastically reduced. This unexpected result occurs because aerosol particles from burning coal block solar radiation from warming the ground.

Building Resilience Against the Worst

The worst-case scenarios could be utilized in planning the building of critical national infrastructure, such as housing developments, energy plants and urban drainage systems. Awareness of these environmental threats could also speed the transition to cut greenhouse gas emissions.

The research developed the severe projections using a combination of real-world events, digital projections and scientific theory. These outcomes do not take into account international cascading effects such as the devastation of food supplies and increased conflict.

This work was commissioned as part of a government’s risk assessment framework. Previous assessments have stated that insufficient focus was being paid to high-consequence, low-probability risks.

An independent advisory body has said that the UK needs to "prepare for two degrees of warming" and examine the dangers for four degrees. Earlier government strategies have been labeled being "inadequate" by certain experts.

A national response said: "Global warming is at the heart of our national priorities, both adapting for the future and establishing itself as a renewable energy leader. It is vital that the UK is ready for the impacts."