🔗 Share this article

The direst possible consequences of the climate crisis for the UK have been detailed by scientists, including a blistering 4C increase in average temperatures to a 2-metre increase in ocean levels. Another scenario predicts a decline of 6C in temperature following the collapse of key Atlantic Ocean currents, which would profoundly upset agriculture and power requirements.

Plausible Extremes, Not Predictions

These impacts, some of which are linked to climate tipping points, are viewed as low probability but credible. The scientists stated that these scenarios plugged a hole in risk assessment that had rendered the UK ill-prepared for catastrophic possibilities.

"The climate extremes we have mapped should not be seen as certainties, but they are plausible," commented the professor who led the analysis. "The nation has been formulating policy without the frameworks to assess extreme possibilities. We've now given policymakers what they need to get ready for future conditions they wish to avoid, but can’t afford to ignore."

A Range of Extreme Weather Possibilities

A further series of worst-case scenarios sets out the potential extent of harsh climate between now and the end of the century. These show that thermometer readings could skyrocket in some months by up to 6C higher than historical levels, while precipitation could be 300% of normal levels.

The probability of the extreme scenarios happening cannot be precisely determined due to unknown factors about what measures will be taken to combat global warming and how the planet's climate will respond. This analysis was likened to security threat evaluations or stress tests for the banking sector.

Critical Possibility Elements

• Four-Degree Warming: Global temperatures soaring past 4C by 2100 could happen if climate action fails or if strong feedback loops including the tropical forests dying unleash its vast reserves of carbon. This would lead to severe and lengthy heatwaves and dry spells hitting the UK in summer.
• AMOC Shutdown: A major ocean current, the AMOC, is losing strength and becoming unstable due to global heating. A full shutdown commencing by 2030 would lead to a 6C cooling in the UK. "Farming would struggle enormously and water resources would be fundamentally reshaped," explained the lead researcher.
• Rapid Sea Level Rise: A increase of 2.0-2.2 metres around the UK by 2100 could occur if polar ice in Greenland and Antarctica collapse rapidly, flooding coastal cities and towns. Unlike the other scenarios, this threat is already understood by planners.
• Pollution Paradox: Temperatures could also be increased by about 0.75C if pollution from industry is rapidly cleaned up. This paradoxical outcome occurs because tiny specks from industrial activity block solar radiation from reaching the ground.

Building Resilience Against the Unthinkable

The worst-case scenarios could be applied to guide the construction of major projects, including housing developments, nuclear power stations and urban drainage systems. Awareness of these climate risks could also accelerate the transition to reduce carbon pollution.

The analysis formulated the worst-case scenarios using a combination of real-world events, climate models and scientific theory. The scenarios omit potential global problems including the global food shortages and geopolitical instability.

The project was initiated as part of a national risk assessment framework. Previous assessments have cautioned that insufficient focus was being paid to low‐likelihood but high‐impact risks.

An independent advisory body has stated that the UK needs to "prepare for two degrees of warming" and assess the risks for 4C. Past policy documents have been described as being "very weak" by some observers.

A government spokesperson noted: "The climate emergency is at the heart of the country's focus, both building resilience and transitioning to a low-carbon economy. It is essential that the UK is ready for the consequences."