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The most severe projected effects of the climate emergency for the UK have been mapped by scientists, encompassing a blistering 4C increase in temperatures to a 2-metre rise in ocean levels. Another scenario foresees a decline of 6C in temperatures following the collapse of crucial Atlantic Ocean currents, which would severely impact food production and power requirements.

Plausible Events, Not Guarantees

These impacts, some of which are linked to climate tipping points, are viewed as unlikely but credible. The team explained that these models filled a gap in forecasting that had left the UK not ready for worst-case results.

"The climate extremes we have detailed aren’t predictions, but they are possible," stated the lead researcher who oversaw the analysis. "The UK has been planning lacking the methods to plan for catastrophic outcomes. We've now provided decision-makers what they need to plan for future conditions they pray never occur, but dare not dismiss."

A Spectrum of Harsh Climate Scenarios

Another collection of severe models details the projected severity of harsh climate between now and the close of the 2100s. These suggest that temperatures could skyrocket in some months by up to 6C above historical levels, while rainfall could be three times typical amounts.

The probability of the extreme scenarios happening cannot be precisely determined due to a lack of certainty about what action will be taken to tackle global warming and how the Earth's systems will react. This approach was described as similar to defence planning or stress tests for economic stability.

Major Possibility Elements

• Four-Degree Warming: Worldwide averages soaring past 4C by 2100 could occur if emissions cuts collapses or if vicious cycles such as the Amazon basin becoming a net carbon source emit its enormous store of carbon. This would result in intense and enduring heatwaves and dry spells hitting the UK in summer.
• AMOC Shutdown: A critical sea current, the North Atlantic current, is weakening and losing stability due to global heating. A full shutdown commencing by 2030 would lead to a 6C cooling in the UK. "Agriculture would face immense difficulties and freshwater availability would be fundamentally reshaped," noted Arnell.
• Sudden Ocean Inundation: A rise of 2.0-2.2 metres around the UK by 2100 could happen if ice sheets in the Arctic and Antarctic melt abruptly, flooding coastal cities and towns. In contrast to the other scenarios, this risk is already recognized by infrastructure experts.
• Clean Air Warming: Temperatures could also be increased by about 0.75C if airborne particulates is rapidly cleaned up. This counterintuitive effect occurs because aerosol particles from fossil fuel combustion reflect solar radiation from warming the ground.

Building Resilience Against the Extreme

The severe models could be applied to guide the development of critical national infrastructure, including new towns, nuclear power stations and urban drainage systems. Understanding these climate risks could also speed the drive to slash carbon pollution.

The study formulated the severe projections using a blend of real-world events, climate models and scientific theory. The possibilities exclude potential global problems such as the global food shortages and increased conflict.

The project was commissioned as part of a government’s risk assessment framework. Earlier reports have cautioned that too little consideration was being given to catastrophic yet improbable risks.

Official experts has said that the UK must "adapt to 2C" and examine the threats for severe warming. Past policy documents have been described as being "inadequate" by certain experts.

An official statement noted: "Global warming is at the heart of this government’s agenda, both building resilience and transitioning to a low-carbon economy. It is essential that the UK is prepared for the consequences."