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The most severe possible consequences of the climate emergency for the UK have been outlined by experts, ranging from a blistering 4C rise in average temperatures to a two-metre increase in sea level. A separate possibility envisions a plunge of 6C in temperatures following the shutdown of crucial Atlantic Ocean currents, which would severely impact food production and power requirements.

Plausible Events, Not Forecasts

These effects, some of which are connected to climate tipping points, are seen as improbable but credible. The researchers said that these models addressed a shortfall in forecasting that had rendered the UK not ready for extreme outcomes.

"The climate extremes we have detailed are not forecasts, but they are possible," said the professor who oversaw the research. "The UK has been formulating policy lacking the tools to test against worst-case scenarios. We've now supplied decision-makers what they need to prepare for environmental results they wish to avoid, but can’t afford to ignore."

A Range of Extreme Weather Possibilities

A second set of dire projections maps the possible scale of harsh climate between now and the year 2100. These indicate that temperatures could rocket in certain periods by up to 6C higher than historical levels, while rainfall could be three times standard measurements.

The probability of the catastrophic events occurring cannot be precisely determined due to a lack of certainty about what action will be enacted to tackle climate change and how the climate system will behave. This analysis was likened to defence planning or stress tests for financial systems.

Key Scenario Details

• Four-Degree Warming: Worldwide averages soaring past 4C by 2100 could transpire if international cooperation fails or if powerful amplifying effects such as the Amazon rainforest perishing emit its huge repository of carbon. This would lead to extreme and prolonged heat domes and water shortages plaguing the UK in summer.
• Atlantic Current Collapse: A major ocean current, the North Atlantic current, is slowing down and becoming unstable due to ocean warming. A full shutdown commencing by 2030 would lead to a six-degree temperature drop in the UK. "Crop production would struggle enormously and water resources would be fundamentally reshaped," explained the professor.
• Accelerated Coastal Flooding: A surge of 2.0-2.2 metres around the UK by 2100 could happen if ice sheets in Greenland and Antarctica collapse rapidly, inundating low-lying areas. Differing from the other scenarios, this possibility is already recognized by infrastructure experts.
• Aerosol Effect: Temperatures could also be pushed higher by about 0.75C if airborne particulates is rapidly cleaned up. This counterintuitive effect occurs because aerosol particles from burning coal scatter sunlight from warming the ground.

Building Resilience Against the Unthinkable

The worst-case scenarios could be used to inform the development of critical national infrastructure, including expanded cities, power generation facilities and urban drainage systems. Knowledge about these environmental threats could also accelerate the push to reduce fossil fuel emissions.

The research formulated the extreme models using a mix of real-world events, computer simulations and climate physics. These outcomes omit international cascading effects including the devastation of food supplies and resource wars.

This work was commissioned as part of a official risk assessment framework. Previous assessments have warned that not enough attention was being allocated to high-consequence, low-probability risks.

An independent advisory body has stated that the UK needs to "prepare for two degrees of warming" and assess the threats for four degrees. Earlier government strategies have been criticised as being "very weak" by certain experts.

A government spokesperson noted: "The climate emergency is at the center of the country's focus, both building resilience and establishing itself as a renewable energy leader. It is vital that the UK is prepared for the consequences."