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The direst potential impacts of the climate crisis for the UK have been detailed by scientists, ranging from a searing 4C increase in temperatures to a 2-metre rise in sea level. A separate possibility predicts a plunge of 6C in temperature following the collapse of critical Atlantic Ocean currents, which would massively disrupt food production and energy needs.

Credible Outcomes, Not Predictions

These impacts, certain ones are linked to climate tipping points, are seen as improbable but plausible. The scientists said that these scenarios filled a gap in forecasting 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 credible," commented Nigel Arnell who led the analysis. "Britain has been making preparations without the frameworks to test against worst-case scenarios. We've now supplied planners what they need to prepare for environmental results they wish to avoid, but dare not dismiss."

A Range of Severe Conditions Scenarios

A further series of dire projections sets out the possible scale of severe conditions between now and the year 2100. These indicate that temperatures could rocket in some months by up to 6C above average, while precipitation could be 300% of typical amounts.

The probability of the extreme scenarios occurring could not be calculated due to a lack of certainty about what action will be taken to address climate change and how the planet's climate will behave. This approach was compared to defence planning or scenario planning for economic stability.

Critical Scenario Details

• Four-Degree Warming: Global temperatures exceeding 4C by 2100 could occur if international cooperation collapses or if powerful amplifying effects like the Amazon basin dying unleash its huge repository of carbon. This would cause severe and lengthy heat domes and dry spells affecting the UK in summer.
• Atlantic Current Collapse: A major ocean current, the AMOC, is losing strength and showing signs of collapse due to climate change. A full shutdown beginning in 2030 would lead to a six-degree temperature drop in the UK. "Farming would struggle enormously and water resources would be drastically changed," noted the lead researcher.
• Accelerated Coastal Flooding: A increase of 2.0-2.2 metres around the UK by 2100 could happen if polar ice in the Arctic and Antarctic melt abruptly, inundating coastal cities and towns. Unlike the other scenarios, this risk is already recognized by infrastructure experts.
• Pollution Paradox: Global averages could also be pushed higher by about 0.75C if airborne particulates is drastically reduced. This unexpected result occurs because tiny specks from burning coal block solar radiation from reaching the ground.

Preparing for the Extreme

The severe models could be used to inform the development of major projects, such as expanded cities, power generation facilities and flood defences. Knowledge about these climate risks could also hasten the push to cut greenhouse gas emissions.

The analysis developed the extreme models using a blend of past data and records, digital projections and scientific theory. These outcomes do not take into account international cascading effects such as the global food shortages and geopolitical instability.

The project was requested as part of a official risk assessment framework. Independent analyses have warned that not enough attention was being paid to low‐likelihood but high‐impact risks.

Official experts has stated that the UK needs to "adapt to 2C" and examine the threats for 4C. Past policy documents have been described as being "very weak" by certain experts.

A national response said: "The climate emergency is at the heart of this government’s agenda, both building resilience and establishing itself as a clean energy superpower. It is essential that the UK is ready for the effects."