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The most severe projected effects of the climate crisis for the UK have been mapped by researchers, encompassing a blistering 4C increase in average temperatures to a two-metre surge in sea levels. Another scenario predicts a decline of 6C in temperature following the failure of key Atlantic Ocean currents, which would profoundly upset food production and power requirements.

Plausible Events, Not Forecasts

These effects, some of which are linked to irreversible climate shifts, are viewed as low probability but possible. The team said that these projections addressed a shortfall in risk assessment that had left the UK not ready for catastrophic possibilities.

"The worst-case scenarios we have outlined are not forecasts, but they are possible," said the professor who led the analysis. "Britain has been planning without the frameworks to plan for worst-case scenarios. We've now supplied decision-makers what they need to get ready for future conditions they pray never occur, but can’t afford to ignore."

A Suite of Extreme Weather Scenarios

A further series of worst-case scenarios sets out the projected severity of harsh climate between now and the close of the 2100s. These suggest that temperatures could soar in particular seasons by up to 6C higher than the norm, while rainfall could be 300% of normal levels.

The probability of the worst-case outcomes occurring cannot be precisely determined due to a lack of certainty about what measures will be enacted to address global heating and how the climate system will behave. This analysis was compared to security threat evaluations or stress tests for the banking sector.

Key Outcome Details

• Severe Heating: Planetary heating rising well above 4C by 2100 could happen if international cooperation collapses or if powerful amplifying effects such as the Amazon rainforest perishing release its enormous store of carbon. This would lead to severe and lengthy heatwaves and dry spells hitting the UK in summer.
• AMOC Shutdown: A key circulation system, the AMOC, is weakening and showing signs of collapse due to ocean warming. A complete failure beginning in 2030 would lead to a six-degree temperature drop in the UK. "Agriculture would be severely challenged and water resources would be drastically changed," said the professor.
• Sudden Ocean Inundation: A rise of 2.0-2.2 metres around the UK by 2100 could occur if polar ice in the Arctic and Antarctic disintegrate quickly, flooding coastal cities and towns. Unlike the other scenarios, this threat is already known by coastal engineers.
• Pollution Paradox: Temperatures could also be pushed higher by about 0.75C if pollution from industry is rapidly cleaned up. This unexpected result occurs because tiny specks from burning coal block sunlight from reaching the ground.

Planning for the Worst

These dire projections could be applied to guide the development of critical national infrastructure, for example housing developments, power generation facilities and flood defences. Awareness of these environmental threats could also speed the push to reduce fossil fuel emissions.

The research developed the worst-case scenarios using a mix of real-world events, digital projections and scientific theory. The possibilities omit broader worldwide issues like the agricultural collapse and increased conflict.

The project was initiated as part of a national risk assessment framework. Earlier reports have warned that too little consideration was being paid to catastrophic yet improbable risks.

The government's climate advisors has recommended that the UK must "become resilient to moderate heating" and examine the dangers for four degrees. Earlier government strategies have been labeled being "very weak" by environmental groups.

A government spokesperson said: "Global warming is at the heart of this government’s agenda, both preparing for impacts and establishing itself as a clean energy superpower. It is essential that the UK is prepared for the consequences."