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The most severe potential impacts of the climate emergency for the UK have been detailed by experts, including a scorching 4C jump in temperatures to a two-metre rise in ocean levels. Another scenario foresees a plunge of 6C in temperature following the collapse of critical Atlantic Ocean currents, which would massively disrupt food production and power requirements.

Possible Events, Not Predictions

These impacts, a number of which are connected to irreversible climate shifts, are considered as unlikely but plausible. The team stated that these projections addressed a shortfall in planning that had left the UK ill-prepared for worst-case results.

"The worst-case scenarios we have mapped are not forecasts, but they are credible," said the professor who oversaw the research. "Britain has been making preparations without the tools to test against catastrophic outcomes. We've now given decision-makers what they need to plan for climate outcomes they pray never occur, but must not overlook."

A Range of Severe Conditions Scenarios

A further series of dire projections maps the potential extent of severe conditions between now and the year 2100. These suggest that thermometer readings could rocket in certain periods by up to 6C higher than average, while rainfall could be triple standard measurements.

The likelihood of the extreme scenarios coming to pass remains uncertain due to uncertainty about what action will be enacted to address climate change and how the climate system will respond. This research was described as similar to defence planning or stress tests for the banking sector.

Critical Scenario Highlights

• Severe Heating: Global temperatures rising well above 4C by 2100 could transpire if international cooperation collapses or if strong feedback loops including the tropical forests becoming a net carbon source emit its enormous store of carbon. This would lead to intense and enduring heat domes and dry spells hitting the UK in summer.
• Atlantic Current Collapse: A critical sea current, the Atlantic meridional overturning circulation (Amoc), is weakening and becoming unstable due to global heating. A full shutdown commencing by 2030 would lead to a 6C cooling in the UK. "Agriculture would struggle enormously and freshwater availability would be completely altered," said the professor.
• Sudden Ocean Inundation: A surge of 2.0-2.2 metres around the UK by 2100 could take place if polar ice in the polar regions disintegrate quickly, flooding coastal cities and towns. Unlike the other scenarios, this risk is already understood by coastal engineers.
• Pollution Paradox: Global averages could also be driven up by about 0.75C if pollution from industry is rapidly cleaned up. This paradoxical outcome occurs because tiny specks from industrial activity scatter sunlight from reaching the ground.

Planning for the Worst

These dire projections could be applied to guide the development of critical national infrastructure, including expanded cities, energy plants and urban drainage systems. Awareness of these climate risks could also accelerate the drive to cut fossil fuel emissions.

The study created the severe projections using a blend of past data and records, digital projections and scientific theory. The scenarios omit international cascading effects including the devastation of food supplies and geopolitical instability.

The research was initiated as part of a national risk assessment framework. Previous assessments 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 evaluate the risks for 4C. Past policy documents have been labeled being "very weak" by some observers.

A government spokesperson said: "The climate emergency is at the core of this government’s agenda, both building resilience and establishing itself as a renewable energy leader. It is vital that the UK is resilient for the impacts."