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The gravest possible consequences of the climate emergency for the UK have been detailed by experts, ranging from a scorching 4C jump in average temperatures to a 2-metre surge in ocean levels. Another scenario predicts a plunge of 6C in temperatures following the failure of critical Atlantic Ocean currents, which would massively disrupt agriculture and energy needs.

Credible Extremes, Not Predictions

These effects, some of which are connected to climate tipping points, are considered as unlikely but credible. The team stated that these scenarios plugged a hole in forecasting that had rendered the UK not ready for catastrophic possibilities.

"The severe weather events we have detailed are not forecasts, but they are plausible," said Nigel Arnell who oversaw the study. "The nation has been planning in the absence of the tools to plan for extreme possibilities. We've now provided policymakers what they need to prepare for future conditions they hope never happen, but can’t afford to ignore."

A Spectrum of Extreme Weather Possibilities

Another collection of worst-case scenarios sets out the potential extent of severe conditions between now and the close of the 2100s. These show that thermometer readings could soar in certain periods by up to 6C above average, while precipitation could be three times normal levels.

The chance of the worst-case outcomes coming to pass cannot be precisely determined due to unknown factors about what measures will be taken to tackle climate change and how the planet's climate will react. This research was compared to security threat evaluations or stress tests for financial systems.

Key Scenario Elements

• Severe Heating: Worldwide averages rising well above 4C by 2100 could transpire if international cooperation collapses or if powerful amplifying effects such as the Amazon rainforest perishing release its vast reserves of carbon. This would result in extreme and prolonged heatwaves and droughts hitting the UK in summer.
• Ocean Circulation Failure: A key circulation system, the AMOC, is weakening and losing stability due to global heating. A collapse beginning in 2030 would lead to a six-degree temperature drop in the UK. "Agriculture would struggle enormously and water resources would be drastically changed," explained Arnell.
• Accelerated Coastal Flooding: A rise of 2.0-2.2 metres around the UK by 2100 could occur if glaciers in the Arctic and Antarctic disintegrate quickly, inundating coastal cities and towns. Differing from the other scenarios, this risk is already recognized by coastal engineers.
• Clean Air Warming: Global averages could also be driven up by about 0.75C if industrial aerosols is sharply cut. This unexpected result occurs because pollution particles from fossil fuel combustion reflect sunlight from reaching the ground.

Planning for the Extreme

These dire projections could be used to inform the construction of critical national infrastructure, such as expanded cities, energy plants and flood defences. Understanding these future hazards could also hasten the drive to slash fossil fuel emissions.

The study developed the extreme models using a blend of real-world events, digital projections and established principles. These outcomes do not take into account broader worldwide issues including the global food shortages and geopolitical instability.

The research was requested as part of a government’s adaptation planning initiative. Independent analyses have cautioned that not enough attention was being given to catastrophic yet improbable risks.

Official experts has recommended that the UK must "prepare for two degrees of warming" and examine the dangers for four degrees. Earlier government strategies have been labeled being "inadequate" by certain experts.

An official statement said: "Climate change is at the center of our national priorities, both adapting for the future and establishing itself as a renewable energy leader. It is vital that the UK is prepared for the impacts."