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The most severe potential impacts of the climate emergency for the UK have been outlined by scientists, including a scorching 4C jump in average temperatures to a 2-metre increase in sea levels. Another scenario foresees a plunge of 6C in temperatures following the failure of crucial Atlantic Ocean currents, which would massively disrupt agriculture and energy demand.

Plausible Events, Not Predictions

These consequences, certain ones are associated with irreversible climate shifts, are seen as unlikely but plausible. The scientists said that these scenarios plugged a hole in planning that had left the UK not ready for extreme outcomes.

"The worst-case scenarios we have detailed should not be seen as certainties, but they are plausible," commented the lead researcher who oversaw the study. "Britain has been making preparations lacking the methods to plan for catastrophic outcomes. We've now supplied planners what they need to plan for future conditions they pray never occur, but must not overlook."

A Spectrum of Extreme Weather Projections

A further series of dire projections sets out the possible scale of harsh climate between now and the close of the 2100s. These indicate that temperatures could soar in certain periods by up to 6C higher than average, while rainfall could be 300% of typical amounts.

The chance of the extreme scenarios coming to pass could not be calculated due to uncertainty about what steps will be taken to address climate change and how the planet's climate will behave. This approach was likened to national security risk assessments or scenario planning for financial systems.

Critical Possibility Elements

• Four-Degree Warming: Worldwide averages exceeding 4C by 2100 could happen if international cooperation collapses or if vicious cycles including the Amazon rainforest becoming a net carbon source unleash its huge repository of carbon. This would result in severe and lengthy heatwaves and dry spells hitting the UK in summer.
• Atlantic Current Collapse: A major ocean current, the North Atlantic current, is losing strength and becoming unstable due to climate change. A collapse beginning in 2030 would lead to a drastic cooling in the UK. "Agriculture would struggle enormously and water supplies would be drastically changed," said the professor.
• Rapid Sea Level Rise: A increase of 2.0-2.2 metres around the UK by 2100 could occur if ice sheets in Greenland and Antarctica collapse rapidly, submerging coastal cities and towns. In contrast to the other scenarios, this possibility is already recognized 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 aerosol particles from industrial activity reflect sunlight from warming the ground.

Planning for the Extreme

These dire projections could be applied to guide the development of critical national infrastructure, such as new towns, energy plants and urban drainage systems. Knowledge about these environmental threats could also speed the drive to reduce carbon pollution.

The study formulated the extreme models using a blend of past data and records, computer simulations and established principles. The possibilities do not take into account broader worldwide issues like the agricultural collapse and resource wars.

The research was commissioned as part of a official climate resilience programme. Previous assessments have stated that insufficient focus was being paid to high-consequence, low-probability risks.

Official experts has said that the UK must "prepare for two degrees of warming" and assess the risks for four degrees. Past policy documents have been described as being "insufficient" by environmental groups.

A national response noted: "The climate emergency is at the core of this government’s agenda, both preparing for impacts and establishing itself as a renewable energy leader. It is crucial that the UK is resilient for the consequences."