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The gravest possible consequences of the climate crisis for the UK have been outlined by scientists, ranging from a searing 4C increase in average temperatures to a 6.5-foot rise in ocean levels. A separate possibility envisions a drop of 6C in temperatures following the collapse of crucial Atlantic Ocean currents, which would massively disrupt farming and energy needs.

Plausible Events, Not Predictions

These consequences, certain ones are linked to climate tipping points, are viewed as unlikely but credible. The researchers explained that these scenarios addressed a shortfall in planning that had rendered the UK not ready for worst-case results.

"The climate extremes we have detailed aren’t predictions, but they are plausible," stated Nigel Arnell who led the study. "The UK has been making preparations without the methods to test against extreme possibilities. We've now provided planners what they need to get ready for climate outcomes they pray never occur, but must not overlook."

A Range of Extreme Weather Possibilities

Another collection of worst-case scenarios maps the projected severity of extreme weather between now and the end of the century. These show that thermometer readings could skyrocket in particular seasons by up to 6C above average, while rainfall could be triple typical amounts.

The probability of the catastrophic events coming to pass cannot be precisely determined due to a lack of certainty about what measures will be enacted to tackle climate change and how the planet's climate will behave. This approach was likened to defence planning or stress tests for the banking sector.

Key Scenario Elements

• Severe Heating: Planetary heating exceeding 4C by 2100 could happen if international cooperation fails or if strong feedback loops like the Amazon basin becoming a net carbon source unleash its huge repository of carbon. This would lead to severe and lengthy heatwaves and water shortages hitting the UK in summer.
• Atlantic Current Collapse: A critical sea current, the North Atlantic current, is slowing down and showing signs of collapse due to global heating. A complete failure starting around 2030 would lead to a 6C cooling in the UK. "Crop production would be severely challenged and water supplies would be drastically changed," noted Arnell.
• Accelerated Coastal Flooding: A increase of 2.0-2.2 metres around the UK by 2100 could take place if glaciers in Greenland and Antarctica collapse rapidly, submerging seaside communities. In contrast to the other scenarios, this risk is already recognized by coastal engineers.
• Pollution Paradox: Global averages could also be increased by about 0.75C if airborne particulates is sharply cut. This unexpected result occurs because aerosol particles from industrial activity block sunlight from reaching the ground.

Planning for the Worst

The severe models could be used to inform the building of long-term infrastructure, for example housing developments, nuclear power stations and water management networks. Knowledge about these environmental threats could also accelerate the push to reduce greenhouse gas emissions.

The analysis created the severe projections using a blend of past data and records, climate models and climate physics. The possibilities do not take into account international cascading effects such as the agricultural collapse and increased conflict.

The research was initiated as part of a government’s risk assessment framework. Independent analyses have cautioned that too little consideration was being allocated to low‐likelihood but high‐impact risks.

An independent advisory body has said that the UK must "become resilient to moderate heating" and evaluate the dangers for severe warming. Past policy documents have been labeled being "very weak" by certain experts.

An official statement noted: "The climate emergency is at the heart of the country's focus, both preparing for impacts and establishing itself as a renewable energy leader. It is crucial that the UK is resilient for the consequences."