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The gravest projected effects of the climate emergency for the UK have been outlined by experts, ranging from a scorching 4C increase in temperatures to a 6.5-foot rise in sea levels. An alternative projection foresees a plunge of 6C in temperatures following the shutdown of crucial Atlantic Ocean currents, which would massively disrupt farming and energy needs.

Plausible Events, Not Forecasts

These consequences, a number of which are linked to climate tipping points, are viewed as improbable but possible. The scientists said that these projections addressed a shortfall in risk assessment that had left the UK unprepared for catastrophic possibilities.

"The worst-case scenarios we have outlined should not be seen as certainties, but they are possible," stated the professor who led the research. "Britain has been planning without the frameworks to test against worst-case scenarios. We've now supplied decision-makers what they need to get ready for future conditions they wish to avoid, but dare not dismiss."

A Range of Extreme Weather Possibilities

Another collection of worst-case scenarios maps the possible scale of severe conditions between now and the end of the century. These show that temperatures could skyrocket in certain periods by up to 6C above average, while rainfall could be 300% of standard measurements.

The likelihood of the worst-case outcomes occurring cannot be precisely determined due to a lack of certainty about what action will be taken to address global heating and how the Earth's systems will react. This approach was compared to security threat evaluations or resilience checks for financial systems.

Key Possibility Highlights

• 4C Temperature Rise: Planetary heating exceeding 4C by 2100 could transpire if climate action breaks down or if powerful amplifying effects such as the Amazon basin dying unleash its enormous store of carbon. This would lead to extreme and prolonged heatwaves and droughts hitting the UK in summer.
• AMOC Shutdown: A critical sea current, the AMOC, is slowing down and losing stability 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 completely altered," explained Arnell.
• Rapid Sea Level Rise: A rise of 2.0-2.2 metres around the UK by 2100 could take place if polar ice in the polar regions disintegrate quickly, inundating coastal cities and towns. Unlike the other scenarios, this possibility is already known by planners.
• Clean Air Warming: Temperatures could also be pushed higher by about 0.75C if pollution from industry is sharply cut. This counterintuitive effect occurs because pollution particles from industrial activity block solar radiation from warming the ground.

Preparing for the Unthinkable

The severe models could be used to inform the development of critical national infrastructure, including expanded cities, nuclear power stations and water management networks. Knowledge about these environmental threats could also hasten the transition to cut greenhouse gas emissions.

The research created the worst-case scenarios using a combination of observed and historical experience, digital projections and climate physics. The scenarios do not take into account potential global problems including the global food shortages and increased conflict.

The project was commissioned as part of a government’s risk assessment framework. Previous assessments have cautioned that insufficient focus was being paid to catastrophic yet improbable risks.

The government's climate advisors has recommended that the UK must "adapt to 2C" and assess the risks for severe warming. Past policy documents have been labeled being "inadequate" by environmental groups.

A national response said: "Climate change 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 impacts."