Significant Disruption Ahead: The United Kingdom's Worst-Case Global Warming Scenarios Revealed by Scientists

The most severe possible consequences of the climate emergency for the UK have been outlined by researchers, ranging from a searing 4C rise in temperatures to a 2-metre rise in sea level. Another scenario foresees a drop of 6C in temperature following the failure of key Atlantic Ocean currents, which would severely impact farming and power requirements.

Possible Outcomes, Not Predictions

These impacts, some of which are associated with irreversible climate shifts, are considered as unlikely but plausible. The scientists stated that these models plugged a hole in forecasting that had left the UK not ready for extreme outcomes.

"The worst-case scenarios we have outlined should not be seen as certainties, but they are plausible," stated the lead researcher who led the research. "The nation has been formulating policy without the frameworks to test against worst-case scenarios. We've now provided decision-makers what they need to prepare for future conditions they pray never occur, but dare not dismiss."

A Suite of Harsh Climate Scenarios

A further series of severe models sets out the potential extent of severe conditions between now and the close of the 2100s. These suggest that thermometer readings could soar in certain periods by up to 6C higher than average, while rainfall could be three times standard measurements.

The likelihood of the catastrophic events happening remains uncertain due to uncertainty about what steps will be taken to combat climate change and how the Earth's systems will behave. This research was likened to security threat evaluations or scenario planning for financial systems.

Major Scenario Elements

• Four-Degree Warming: Worldwide averages rising well above 4C by 2100 could happen if climate action breaks down or if strong feedback loops like the Amazon rainforest becoming a net carbon source emit its vast reserves of carbon. This would cause severe and lengthy heat domes and water shortages plaguing the UK in summer.
• AMOC Shutdown: A key circulation system, the Atlantic meridional overturning circulation (Amoc), is losing strength and becoming unstable due to global heating. A full shutdown commencing by 2030 would lead to a drastic cooling in the UK. "Farming would face immense difficulties and freshwater availability would be completely altered," said Arnell.
• Accelerated Coastal Flooding: A rise of 2.0-2.2 metres around the UK by 2100 could happen if glaciers in the Arctic and Antarctic disintegrate quickly, inundating coastal cities and towns. Unlike the other scenarios, this threat is already known by planners.
• Aerosol Effect: Global averages could also be increased by about 0.75C if pollution from industry is rapidly cleaned up. This unexpected result occurs because pollution particles from fossil fuel combustion block sunlight from reaching the ground.

Planning for the Worst

These dire projections could be used to inform the development of critical national infrastructure, including new towns, energy plants and flood defences. Knowledge about these climate risks could also hasten the push to slash greenhouse gas emissions.

The research created the extreme models using a combination of observed and historical experience, digital projections and climate physics. The possibilities exclude international cascading effects such as the global food shortages and increased conflict.

The research was commissioned as part of a government’s climate resilience programme. Independent analyses have stated that insufficient focus 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 examine the dangers for severe warming. Past policy documents have been criticised as being "very weak" by some observers.

A national response noted: "Global warming is at the core of the country's focus, both adapting for the future and transitioning to a renewable energy leader. It is essential that the UK is ready for the consequences."