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The direst potential impacts of the climate emergency for the UK have been detailed by experts, encompassing a blistering 4C increase in mean temperatures to a 2-metre increase in ocean levels. A separate possibility foresees a drop of 6C in temperatures following the collapse of crucial Atlantic Ocean currents, which would massively disrupt food production and energy demand.

Credible Extremes, Not Forecasts

These impacts, certain ones are connected to critical climate thresholds, are seen as low probability but plausible. The scientists said that these projections plugged a hole in forecasting that had left the UK ill-prepared for extreme outcomes.

"The severe weather events we have outlined aren’t predictions, but they are possible," said Nigel Arnell who directed the research. "Britain has been making preparations lacking the tools to test against catastrophic outcomes. We've now given planners what they need to plan for environmental results they pray never occur, but can’t afford to ignore."

A Range of Harsh Climate Possibilities

A further series of severe models details the projected severity of severe conditions between now and the end of the century. These show that thermometer readings could soar in certain periods by up to 6C above average, while precipitation could be triple normal levels.

The chance of the worst-case outcomes occurring could not be calculated due to a lack of certainty about what measures will be taken to combat global heating and how the planet's climate will respond. This approach was likened to national security risk assessments or resilience checks for financial systems.

Critical Outcome Highlights

• Four-Degree Warming: Global temperatures soaring past 4C by 2100 could transpire if climate action collapses or if strong feedback loops including the Amazon basin dying unleash its enormous store of carbon. This would lead to extreme and prolonged heat domes and water shortages plaguing the UK in summer.
• Atlantic Current Collapse: A critical sea current, the North Atlantic current, is weakening and becoming unstable due to climate change. A full shutdown starting around 2030 would lead to a 6C cooling in the UK. "Crop production would be severely challenged and water resources would be completely altered," said the lead researcher.
• Sudden Ocean Inundation: A increase of 2.0-2.2 metres around the UK by 2100 could occur if polar ice in the Arctic and Antarctic melt abruptly, flooding low-lying areas. Unlike the other scenarios, this threat is already understood by coastal engineers.
• Pollution Paradox: Global averages could also be driven up by about 0.75C if industrial aerosols is rapidly cleaned up. This unexpected result occurs because tiny specks from fossil fuel combustion block sunlight from warming the ground.

Preparing for the Extreme

The worst-case scenarios could be utilized in planning the construction of major projects, such as new towns, power generation facilities and flood defences. Knowledge about these environmental threats could also hasten the transition to cut fossil fuel emissions.

The analysis created the extreme models using a combination of past data and records, computer simulations and scientific theory. These outcomes do not take into account broader worldwide issues such as the global food shortages and increased conflict.

This work was initiated as part of a government’s adaptation planning initiative. Independent analyses have stated that insufficient focus was being paid to low‐likelihood but high‐impact risks.

An independent advisory body has said that the UK needs to "prepare for two degrees of warming" and evaluate the dangers for severe warming. Past policy documents have been criticised as being "insufficient" by certain experts.

A government spokesperson said: "The climate emergency is at the core of the country's focus, both building resilience and transitioning to a clean energy superpower. It is crucial that the UK is prepared for the impacts."