Profound Upheaval Ahead: Britain's Worst-Case Global Warming Possibilities Revealed by Researchers

The gravest projected effects of the climate emergency for the UK have been detailed by experts, ranging from a scorching 4C rise in temperatures to a two-metre rise in ocean levels. Another scenario envisions a plunge of 6C in temperatures following the shutdown of key Atlantic Ocean currents, which would severely impact food production and power requirements.

Possible Extremes, Not Forecasts

These consequences, a number of which are connected to critical climate thresholds, are viewed as improbable but plausible. The team said that these models addressed a shortfall in risk assessment that had left the UK ill-prepared for extreme outcomes.

"The climate extremes we have outlined are not forecasts, but they are possible," stated the professor who led the analysis. "Britain has been making preparations without the tools to assess extreme possibilities. We've now given policymakers what they need to plan for future conditions they wish to avoid, but can’t afford to ignore."

A Suite of Extreme Weather Scenarios

Another collection of severe models maps the projected severity of extreme weather between now and the end of the century. These indicate that temperatures could soar in particular seasons by up to 6C higher than the norm, while rainfall could be triple normal levels.

The likelihood of the worst-case outcomes coming to pass could not be calculated due to a lack of certainty about what action will be taken to address global warming and how the planet's climate will respond. This analysis was described as similar to defence planning or stress tests for the banking sector.

Critical Possibility Elements

• Four-Degree Warming: Global temperatures exceeding 4C by 2100 could happen if climate action fails or if strong feedback loops including the tropical forests dying emit its enormous store of carbon. This would cause intense and enduring heatwaves and dry spells affecting the UK in summer.
• AMOC Shutdown: A major ocean current, the North Atlantic current, is weakening and losing stability due to climate change. A collapse beginning in 2030 would lead to a 6C cooling in the UK. "Agriculture would be severely challenged and water supplies would be fundamentally reshaped," noted the professor.
• Accelerated Coastal Flooding: 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 low-lying areas. In contrast to the other scenarios, this possibility is already known by planners.
• Pollution Paradox: Temperatures could also be pushed higher by about 0.75C if airborne particulates is drastically reduced. This counterintuitive effect occurs because pollution particles from burning coal block solar radiation from reaching the ground.

Building Resilience Against the Unthinkable

The severe models could be used to inform the building of long-term infrastructure, such as new towns, energy plants and flood defences. Knowledge about these climate risks could also hasten the transition to cut fossil fuel emissions.

The study developed the worst-case scenarios using a combination of observed and historical experience, climate models and scientific theory. These outcomes do not take into account international cascading effects including the global food shortages and geopolitical instability.

The project was commissioned as part of a national risk assessment framework. Independent analyses have warned that insufficient focus was being paid to low‐likelihood but high‐impact risks.

An independent advisory body has stated that the UK needs to "become resilient to moderate heating" and examine the threats for four degrees. Past policy documents have been criticised as being "very weak" by certain experts.

An official statement said: "Climate change is at the heart of the country's focus, both building resilience and becoming a renewable energy leader. It is crucial that the UK is ready for the impacts."