🔗 Share this article

The gravest projected effects of the climate crisis for the UK have been detailed by scientists, ranging from a scorching 4C rise in mean temperatures to a two-metre surge in sea level. Another scenario predicts a drop of 6C in temperature following the failure of key Atlantic Ocean currents, which would massively disrupt food production and power requirements.

Possible Outcomes, Not Forecasts

These effects, some of which are linked to critical climate thresholds, are viewed as unlikely but plausible. The team explained that these projections filled a gap in planning that had rendered the UK not ready for worst-case results.

"The worst-case scenarios we have outlined are not forecasts, but they are plausible," stated the professor who oversaw the analysis. "The nation has been planning lacking the frameworks to assess catastrophic outcomes. We've now supplied decision-makers what they need to get ready for environmental results they hope never happen, but can’t afford to ignore."

A Suite of Severe Conditions Scenarios

A second set of dire projections sets out the projected severity of severe conditions between now and the end of the century. These indicate that thermometer readings could skyrocket in some months by up to 6C higher than historical levels, while rainfall could be 300% of typical amounts.

The likelihood of the worst-case outcomes happening remains uncertain due to uncertainty about what steps will be enacted to address global warming and how the Earth's systems will behave. This research was described as similar to defence planning or stress tests for the banking sector.

Key Outcome Highlights

• Four-Degree Warming: Worldwide averages exceeding 4C by 2100 could occur if international cooperation breaks down or if vicious cycles such as the tropical forests dying emit its vast reserves of carbon. This would cause extreme and prolonged heatwaves and droughts plaguing the UK in summer.
• AMOC Shutdown: A key circulation system, the AMOC, is slowing down and losing stability due to global heating. A complete failure starting around 2030 would lead to a drastic cooling in the UK. "Agriculture would struggle enormously and water supplies would be fundamentally reshaped," explained Arnell.
• Rapid Sea Level Rise: A rise of 2.0-2.2 metres around the UK by 2100 could occur if ice sheets in Greenland and Antarctica collapse rapidly, submerging low-lying areas. In contrast to the other scenarios, this possibility is already recognized by planners.
• Pollution Paradox: Temperatures could also be pushed higher by about 0.75C if airborne particulates is rapidly cleaned up. This unexpected result occurs because aerosol particles from burning coal reflect solar radiation from reaching the ground.

Building Resilience Against the Worst

The worst-case scenarios could be applied to guide the construction of critical national infrastructure, including housing developments, power generation facilities and water management networks. Knowledge about these climate risks could also speed the push to slash fossil fuel emissions.

The analysis developed the severe projections using a mix of observed and historical experience, climate models and established principles. The scenarios exclude potential global problems such as the devastation of food supplies and resource wars.

The research was requested as part of a national climate resilience programme. Earlier reports have cautioned that insufficient focus was being given to high-consequence, low-probability risks.

The government's climate advisors has recommended that the UK needs to "prepare for two degrees of warming" and assess the threats for severe warming. Previous adaptation plans have been criticised as being "insufficient" by environmental groups.

A national response said: "The climate emergency is at the center of the country's focus, both building resilience and establishing itself as a clean energy superpower. It is essential that the UK is prepared for the consequences."