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The gravest possible consequences of the climate crisis for the UK have been outlined by researchers, ranging from a blistering 4C jump in temperatures to a 2-metre surge in sea levels. A separate possibility envisions a decline of 6C in temperature following the collapse of crucial Atlantic Ocean currents, which would severely impact agriculture and energy needs.

Plausible Events, Not Forecasts

These effects, certain ones are linked to critical climate thresholds, are seen as improbable but credible. The researchers explained that these projections addressed a shortfall in risk assessment that had rendered the UK not ready for worst-case results.

"The worst-case scenarios we have detailed should not be seen as certainties, but they are plausible," commented the professor who led the research. "The nation has been making preparations in the absence of the frameworks to assess catastrophic outcomes. We've now given planners what they need to get ready for climate outcomes they hope never happen, but dare not dismiss."

A Suite of Extreme Weather Scenarios

A further series of dire projections maps the possible scale of harsh climate between now and the close of the 2100s. These suggest that thermometer readings could skyrocket in particular seasons by up to 6C higher than historical levels, while precipitation could be 300% of standard measurements.

The likelihood of the worst-case outcomes happening cannot be precisely determined due to unknown factors about what steps will be implemented to address global warming and how the Earth's systems will behave. This analysis was described as similar to national security risk assessments or resilience checks for financial systems.

Key Possibility Highlights

• 4C Temperature Rise: Global temperatures soaring past 4C by 2100 could occur if climate action collapses or if strong feedback loops like the Amazon rainforest becoming a net carbon source emit its huge repository of carbon. This would result in extreme and prolonged heat domes and dry spells plaguing the UK in summer.
• Ocean Circulation Failure: A key circulation system, the AMOC, is weakening and becoming unstable due to global heating. A collapse starting around 2030 would lead to a drastic cooling in the UK. "Agriculture would struggle enormously and water resources would be drastically changed," explained the lead researcher.
• Rapid Sea Level Rise: A increase of 2.0-2.2 metres around the UK by 2100 could take place if ice sheets in Greenland and Antarctica collapse rapidly, flooding coastal cities and towns. In contrast to the other scenarios, this risk is already recognized by infrastructure experts.
• Pollution Paradox: Global averages could also be increased by about 0.75C if airborne particulates is rapidly cleaned up. This counterintuitive effect occurs because tiny specks from industrial activity reflect sunlight from warming the ground.

Planning for the Unthinkable

The severe models could be applied to guide the construction of long-term infrastructure, such as housing developments, nuclear power stations and urban drainage systems. Understanding these environmental threats could also speed the push to cut carbon pollution.

The study created the worst-case scenarios using a blend of real-world events, climate models and established principles. These outcomes exclude broader worldwide issues like the devastation of food supplies and increased conflict.

The research was requested as part of a government’s risk assessment framework. Previous assessments have cautioned that too little consideration was being given to low‐likelihood but high‐impact risks.

The government's climate advisors has said that the UK must "adapt to 2C" and assess the dangers for 4C. Previous adaptation plans have been described as being "inadequate" by some observers.

A national response noted: "Global warming is at the heart of this government’s agenda, both building resilience and establishing itself as a clean energy superpower. It is vital that the UK is ready for the impacts."