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The most severe possible consequences of the global heating for the UK have been mapped by experts, encompassing a blistering 4C jump in mean temperatures to a 6.5-foot rise in ocean levels. Another scenario predicts a plunge of 6C in temperature following the shutdown of crucial Atlantic Ocean currents, which would severely impact agriculture and energy needs.

Credible Extremes, Not Guarantees

These consequences, certain ones are connected to climate tipping points, are seen as improbable but plausible. The team explained that these models plugged a hole in planning that had rendered the UK ill-prepared for worst-case results.

"The climate extremes we have detailed are not forecasts, but they are credible," commented the professor who oversaw the analysis. "The UK has been making preparations in the absence of the frameworks to plan for extreme possibilities. We've now supplied policymakers what they need to get ready for future conditions they hope never happen, but can’t afford to ignore."

A Spectrum of Severe Conditions Scenarios

Another collection of worst-case scenarios details the potential extent of severe conditions between now and the close of the 2100s. These suggest that temperatures could skyrocket in certain periods by up to 6C higher than average, while rainfall could be triple standard measurements.

The chance of the extreme scenarios occurring remains uncertain due to uncertainty about what measures will be implemented to tackle climate change and how the planet's climate will react. This research was likened to national security risk assessments or stress tests for the banking sector.

Critical Outcome Elements

• Severe Heating: Global temperatures rising well above 4C by 2100 could happen if climate action collapses or if powerful amplifying effects like the Amazon rainforest becoming a net carbon source release its enormous store of carbon. This would lead to intense and enduring heatwaves and droughts hitting the UK in summer.
• AMOC Shutdown: A key circulation system, the North Atlantic current, is weakening and becoming unstable due to climate change. A collapse commencing by 2030 would lead to a drastic cooling in the UK. "Agriculture would struggle enormously and water supplies would be completely altered," explained Arnell.
• Rapid Sea Level Rise: A rise of 2.0-2.2 metres around the UK by 2100 could happen if glaciers in the Arctic and Antarctic collapse rapidly, inundating low-lying areas. Differing from the other scenarios, this risk is already known by coastal engineers.
• Pollution Paradox: Global averages could also be driven up by about 0.75C if industrial aerosols is sharply cut. This counterintuitive effect occurs because pollution particles from industrial activity scatter sunlight from warming the ground.

Planning for the Extreme

These dire projections could be applied to guide the development of long-term infrastructure, including housing developments, energy plants and water management networks. Knowledge about these climate risks could also accelerate the push to slash carbon pollution.

The study created the worst-case scenarios using a mix of real-world events, digital projections and climate physics. These outcomes exclude broader worldwide issues such as the global food shortages and geopolitical instability.

The research was requested as part of a official risk assessment framework. Earlier reports have stated that too little consideration was being allocated to low‐likelihood but high‐impact risks.

An independent advisory body has said that the UK needs to "prepare for two degrees of warming" and evaluate the dangers for 4C. Past policy documents have been described as being "very weak" by certain experts.

A national response noted: "The climate emergency is at the core of this government’s agenda, both building resilience and establishing itself as a clean energy superpower. It is crucial that the UK is prepared for the effects."