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The most severe possible consequences of the climate emergency for the UK have been detailed by experts, encompassing a blistering 4C jump in temperatures to a 2-metre rise in ocean levels. Another scenario envisions a plunge of 6C in temperature following the shutdown of key Atlantic Ocean currents, which would severely impact agriculture and power requirements.

Plausible Events, Not Guarantees

These impacts, certain ones are connected to climate tipping points, are seen as low probability but plausible. The researchers stated that these models plugged a hole in risk assessment that had rendered the UK ill-prepared for catastrophic possibilities.

"The severe weather events we have outlined should not be seen as certainties, but they are possible," stated Nigel Arnell who directed the analysis. "The nation has been making preparations in the absence of the methods to plan for catastrophic outcomes. We've now provided policymakers what they need to plan for future conditions they hope never happen, but must not overlook."

A Spectrum of Severe Conditions Projections

Another collection of dire projections maps the projected severity of severe conditions between now and the year 2100. These suggest that temperatures could skyrocket in particular seasons by up to 6C higher than historical levels, while rainfall could be 300% of standard measurements.

The likelihood of the worst-case outcomes coming to pass remains uncertain due to unknown factors about what action will be implemented to address global warming and how the climate system will react. This approach was described as similar to security threat evaluations or stress tests for economic stability.

Major Possibility Details

• Severe Heating: Global temperatures rising well above 4C by 2100 could transpire if international cooperation fails or if vicious cycles such as the Amazon rainforest dying release its enormous store of carbon. This would cause severe and lengthy heatwaves and water shortages affecting the UK in summer.
• Ocean Circulation Failure: A critical sea current, the Atlantic meridional overturning circulation (Amoc), is weakening and losing stability due to global heating. A collapse starting around 2030 would lead to a six-degree temperature drop in the UK. "Crop production would be severely challenged and water supplies would be completely altered," noted Arnell.
• Sudden Ocean Inundation: A increase of 2.0-2.2 metres around the UK by 2100 could happen if glaciers in the Arctic and Antarctic melt abruptly, submerging low-lying areas. In contrast to the other scenarios, this threat is already understood by coastal engineers.
• Pollution Paradox: Global averages could also be pushed higher by about 0.75C if pollution from industry is drastically reduced. This paradoxical outcome occurs because pollution particles from industrial activity scatter sunlight from reaching the ground.

Preparing for the Worst

The severe models could be applied to guide the development of critical national infrastructure, for example housing developments, energy plants and water management networks. Knowledge about these environmental threats could also accelerate the push to cut fossil fuel emissions.

The analysis created the worst-case scenarios using a blend of observed and historical experience, digital projections and established principles. These outcomes do not take into account broader worldwide issues such as the global food shortages and resource wars.

This work was requested as part of a national climate resilience programme. Previous assessments have warned that not enough attention was being given to catastrophic yet improbable risks.

The government's climate advisors has recommended that the UK needs to "become resilient to moderate heating" and examine the threats for severe warming. Earlier government strategies have been described as being "very weak" by certain experts.

A national response said: "Climate change is at the core of our national priorities, both building resilience and transitioning to a low-carbon economy. It is crucial that the UK is ready for the consequences."