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The most severe potential impacts of the climate emergency for the UK have been mapped by scientists, ranging from a scorching 4C jump in temperatures to a two-metre rise in ocean levels. A separate possibility predicts a drop of 6C in temperature following the collapse of crucial Atlantic Ocean currents, which would massively disrupt farming and energy needs.

Possible Outcomes, Not Predictions

These impacts, certain ones are connected to climate tipping points, are considered as unlikely but possible. The researchers said that these projections filled a gap in forecasting that had rendered the UK not ready for extreme outcomes.

"The severe weather events we have outlined are not forecasts, but they are plausible," commented Nigel Arnell who oversaw the analysis. "The UK has been planning without the methods to test against catastrophic outcomes. We've now supplied planners what they need to plan for climate outcomes they hope never happen, but dare not dismiss."

A Range of Extreme Weather Possibilities

A second set of worst-case scenarios maps the potential extent of harsh climate between now and the year 2100. These indicate that temperatures could soar in certain periods by up to 6C above the norm, while precipitation could be triple typical amounts.

The probability of the extreme scenarios coming to pass remains uncertain due to uncertainty about what measures will be implemented to tackle climate change and how the Earth's systems will behave. This analysis was compared to security threat evaluations or resilience checks for the banking sector.

Key Outcome Details

• Four-Degree Warming: Worldwide averages soaring past 4C by 2100 could transpire if emissions cuts fails or if strong feedback loops such as the tropical forests dying release its huge repository of carbon. This would cause extreme and prolonged heatwaves and dry spells affecting 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 ocean warming. A full shutdown starting around 2030 would lead to a six-degree temperature drop in the UK. "Farming would be severely challenged and freshwater availability would be drastically changed," noted the professor.
• Accelerated Coastal Flooding: A rise of 2.0-2.2 metres around the UK by 2100 could happen if polar ice in Greenland and Antarctica melt abruptly, flooding seaside communities. In contrast to the other scenarios, this risk is already understood by planners.
• Clean Air Warming: Temperatures could also be pushed higher by about 0.75C if industrial aerosols is drastically reduced. This paradoxical outcome occurs because tiny specks from industrial activity block solar radiation from warming the ground.

Planning for the Extreme

The worst-case scenarios could be used to inform the development of critical national infrastructure, for example new towns, nuclear power stations and flood defences. Understanding these environmental threats could also speed the transition to cut greenhouse gas emissions.

The analysis created the worst-case scenarios using a combination of real-world events, climate models and scientific theory. The possibilities do not take into account potential global problems including the agricultural collapse and geopolitical instability.

The project was requested as part of a national risk assessment framework. Independent analyses have stated that not enough attention was being given to low‐likelihood but high‐impact risks.

Official experts has said that the UK must "become resilient to moderate heating" and evaluate the threats for 4C. Earlier government strategies have been described as being "inadequate" by environmental groups.

A national response commented: "Global warming is at the center of our national priorities, both adapting for the future and transitioning to a clean energy superpower. It is crucial that the UK is ready for the impacts."