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The gravest projected effects of the climate emergency for the UK have been outlined by scientists, ranging from a blistering 4C increase in average temperatures to a 6.5-foot surge in sea levels. Another scenario envisions a drop of 6C in temperature following the shutdown of key Atlantic Ocean currents, which would severely impact farming and energy needs.

Credible Extremes, Not Guarantees

These effects, a number of which are linked to climate tipping points, are seen as low probability but possible. The researchers said that these scenarios plugged a hole in risk assessment that had left the UK not ready for worst-case results.

"The worst-case scenarios we have mapped are not forecasts, but they are credible," said the professor who directed the analysis. "The UK has been planning lacking the tools to assess worst-case scenarios. We've now supplied planners what they need to prepare for climate outcomes they pray never occur, but can’t afford to ignore."

A Range of Harsh Climate Possibilities

A further series of dire projections maps the potential extent of extreme weather between now and the close of the 2100s. These show that thermometer readings could soar in particular seasons by up to 6C higher than historical levels, while rainfall could be three times standard measurements.

The chance of the extreme scenarios happening cannot be precisely determined due to unknown factors about what action will be implemented to tackle global heating and how the climate system will behave. This research was compared to security threat evaluations or resilience checks for financial systems.

Major Outcome Details

• Severe Heating: Planetary heating soaring past 4C by 2100 could transpire if climate action fails or if vicious cycles including the Amazon rainforest becoming a net carbon source unleash its enormous store of carbon. This would result in severe and lengthy heat domes and droughts plaguing the UK in summer.
• AMOC Shutdown: A key circulation system, the Atlantic meridional overturning circulation (Amoc), is slowing down and becoming unstable due to ocean warming. A complete failure commencing by 2030 would lead to a six-degree temperature drop in the UK. "Farming would be severely challenged and freshwater availability would be fundamentally reshaped," noted the lead researcher.
• Accelerated Coastal Flooding: A surge of 2.0-2.2 metres around the UK by 2100 could occur if ice sheets in the Arctic and Antarctic collapse rapidly, submerging coastal cities and towns. In contrast to the other scenarios, this possibility is already known by infrastructure experts.
• Aerosol Effect: Global averages could also be driven up by about 0.75C if pollution from industry is sharply cut. This counterintuitive effect occurs because pollution particles from industrial activity scatter sunlight from reaching the ground.

Planning for the Worst

These dire projections could be applied to guide the development of major projects, including expanded cities, nuclear power stations and water management networks. Understanding these climate risks could also accelerate the drive to cut greenhouse gas emissions.

The study created the extreme models using a combination of real-world events, digital projections and scientific theory. These outcomes do not take into account potential global problems like the devastation of food supplies and resource wars.

The project was requested as part of a government’s climate resilience programme. Previous assessments have warned that insufficient focus was being given to catastrophic yet improbable risks.

An independent advisory body has said that the UK needs to "adapt to 2C" and evaluate the risks for four degrees. Earlier government strategies have been described as being "inadequate" by environmental groups.

A government spokesperson noted: "The climate emergency is at the core of our national priorities, both building resilience and transitioning to a clean energy superpower. It is essential that the UK is resilient for the effects."