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The gravest potential impacts of the climate crisis for the UK have been outlined by scientists, encompassing a blistering 4C jump in mean temperatures to a 6.5-foot increase in sea levels. Another scenario predicts a plunge of 6C in temperature following the failure of critical Atlantic Ocean currents, which would massively disrupt food production and power requirements.

Possible Events, Not Forecasts

These effects, a number of which are associated with climate tipping points, are viewed as improbable but possible. The team said that these models plugged a hole in planning that had left the UK not ready for catastrophic possibilities.

"The climate extremes we have outlined are not forecasts, but they are plausible," stated the lead researcher who directed the analysis. "The nation has been planning without the tools to assess worst-case scenarios. We've now supplied decision-makers what they need to plan for climate outcomes they wish to avoid, but dare not dismiss."

A Suite of Extreme Weather Scenarios

Another collection of dire projections details the possible scale of severe conditions between now and the end of the century. These show that thermometer readings could rocket in certain periods by up to 6C higher than average, while precipitation could be triple normal levels.

The probability of the extreme scenarios occurring cannot be precisely determined due to uncertainty about what measures will be taken to address global warming and how the Earth's systems will behave. This research was described as similar to security threat evaluations or scenario planning for the banking sector.

Critical Outcome Highlights

• 4C Temperature Rise: Planetary heating rising well above 4C by 2100 could occur if international cooperation collapses or if strong feedback loops including the tropical forests dying release its vast reserves of carbon. This would cause extreme and prolonged heat domes and dry spells plaguing the UK in summer.
• Ocean Circulation Failure: A critical sea current, the North Atlantic current, is weakening and becoming unstable due to climate change. A complete failure starting around 2030 would lead to a six-degree temperature drop in the UK. "Crop production would struggle enormously and water resources would be fundamentally reshaped," noted the lead researcher.
• Accelerated Coastal Flooding: A rise of 2.0-2.2 metres around the UK by 2100 could take place if polar ice in the polar regions melt abruptly, flooding low-lying areas. Differing from the other scenarios, this threat is already recognized by coastal engineers.
• Aerosol Effect: Temperatures could also be driven up by about 0.75C if airborne particulates is rapidly cleaned up. This counterintuitive effect occurs because tiny specks from burning coal block sunlight from reaching the ground.

Planning for the Extreme

The severe models could be applied to guide the development of critical national infrastructure, including new towns, power generation facilities and water management networks. Understanding these climate risks could also hasten the transition to reduce fossil fuel emissions.

The study created the worst-case scenarios using a blend of real-world events, computer simulations and scientific theory. The scenarios omit broader worldwide issues such as the global food shortages and resource wars.

This work was commissioned as part of a official climate resilience programme. Independent analyses have cautioned that not enough attention was being given to high-consequence, low-probability risks.

Official experts has stated that the UK must "prepare for two degrees of warming" and evaluate the risks for 4C. Previous adaptation plans have been criticised as being "insufficient" by some observers.

A national response commented: "The climate emergency is at the core of the country's focus, both preparing for impacts and establishing itself as a renewable energy leader. It is essential that the UK is ready for the impacts."