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The gravest potential impacts of the climate emergency for the UK have been detailed by researchers, ranging from a searing 4C jump in average temperatures to a 6.5-foot surge in sea levels. Another scenario foresees a plunge of 6C in temperature following the failure of critical Atlantic Ocean currents, which would severely impact agriculture and power requirements.

Plausible Extremes, Not Predictions

These effects, certain ones are associated with irreversible climate shifts, are seen as low probability but credible. The team stated that these projections addressed a shortfall in planning that had rendered the UK ill-prepared for catastrophic possibilities.

"The worst-case scenarios we have outlined should not be seen as certainties, but they are possible," commented the professor who directed the research. "The nation has been making preparations without the tools to plan for catastrophic outcomes. We've now provided decision-makers what they need to get ready for environmental results they hope never happen, but can’t afford to ignore."

A Spectrum of Extreme Weather Possibilities

Another collection of severe models sets out the possible scale of harsh climate between now and the end of the century. These indicate that thermometer readings could soar in particular seasons by up to 6C higher than historical levels, while precipitation could be 300% of standard measurements.

The chance of the catastrophic events occurring could not be calculated due to uncertainty about what steps will be implemented to tackle climate change and how the Earth's systems will behave. This analysis was likened to defence planning or stress tests for economic stability.

Key Scenario Details

• Severe Heating: Global temperatures rising well above 4C by 2100 could occur if climate action breaks down or if strong feedback loops including the Amazon basin perishing release its enormous store of carbon. This would result in intense and enduring heat domes and droughts affecting the UK in summer.
• Ocean Circulation Failure: A key circulation system, the AMOC, is weakening and becoming unstable due to global heating. A complete failure starting around 2030 would lead to a six-degree temperature drop in the UK. "Farming would struggle enormously and water supplies would be drastically changed," explained Arnell.
• Sudden Ocean Inundation: A rise of 2.0-2.2 metres around the UK by 2100 could occur if polar ice in the polar regions melt abruptly, submerging low-lying areas. In contrast to the other scenarios, this risk is already understood by planners.
• Clean Air Warming: Global averages could also be pushed higher by about 0.75C if pollution from industry is rapidly cleaned up. This paradoxical outcome occurs because tiny specks from burning coal reflect sunlight from warming the ground.

Planning for the Unthinkable

The worst-case scenarios could be utilized in planning the building of critical national infrastructure, such as housing developments, energy plants and flood defences. Understanding these environmental threats could also hasten the push to slash greenhouse gas emissions.

The research created the worst-case scenarios using a blend of past data and records, computer simulations and established principles. The scenarios omit potential global problems including the global food shortages and increased conflict.

The project was requested as part of a government’s risk assessment framework. Independent analyses have warned that too little consideration was being allocated to high-consequence, low-probability risks.

An independent advisory body has said that the UK needs to "become resilient to moderate heating" and evaluate the risks for 4C. Previous adaptation plans have been criticised as being "very weak" by some observers.

An official statement said: "Global warming is at the core of the country's focus, both preparing for impacts and transitioning to a clean energy superpower. It is crucial that the UK is resilient for the impacts."