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The most severe potential impacts of the climate emergency for the UK have been mapped by scientists, encompassing a searing 4C increase in average temperatures to a two-metre rise in ocean levels. Another scenario envisions a decline of 6C in temperatures following the failure of critical Atlantic Ocean currents, which would massively disrupt food production and energy needs.

Possible Outcomes, Not Predictions

These impacts, certain ones are linked to irreversible climate shifts, are viewed as low probability but plausible. The researchers said that these models addressed a shortfall in forecasting that had rendered the UK not ready for worst-case results.

"The severe weather events we have detailed are not forecasts, but they are plausible," commented the lead researcher who oversaw the analysis. "The UK has been planning lacking the tools to test against catastrophic outcomes. We've now given planners what they need to get ready for climate outcomes they pray never occur, but can’t afford to ignore."

A Suite of Harsh Climate Possibilities

A further series of worst-case scenarios details the potential extent of harsh climate between now and the close of the 2100s. These indicate that temperatures could rocket in some months by up to 6C higher than the norm, while precipitation could be three times typical amounts.

The probability of the catastrophic events happening cannot be precisely determined due to a lack of certainty about what steps will be taken to address global heating and how the climate system will respond. This analysis was described as similar to national security risk assessments or stress tests for financial systems.

Major Possibility Highlights

• Severe Heating: Worldwide averages exceeding 4C by 2100 could transpire if emissions cuts collapses or if powerful amplifying effects including the Amazon rainforest dying emit its vast reserves of carbon. This would cause intense and enduring heatwaves and water shortages plaguing the UK in summer.
• Ocean Circulation Failure: A key circulation system, the Atlantic meridional overturning circulation (Amoc), is weakening and showing signs of collapse due to global heating. A collapse starting around 2030 would lead to a drastic cooling in the UK. "Farming would be severely challenged and water resources would be fundamentally reshaped," explained Arnell.
• Accelerated Coastal Flooding: A increase of 2.0-2.2 metres around the UK by 2100 could happen if polar ice in the Arctic and Antarctic disintegrate quickly, flooding low-lying areas. Differing from the other scenarios, this possibility is already known by infrastructure experts.
• Aerosol Effect: Temperatures could also be driven up by about 0.75C if industrial aerosols is rapidly cleaned up. This unexpected result occurs because aerosol particles from fossil fuel combustion scatter sunlight from reaching the ground.

Planning for the Unthinkable

These dire projections could be used to inform the development of critical national infrastructure, such as expanded cities, power generation facilities and water management networks. Knowledge about these environmental threats could also speed the drive to reduce fossil fuel emissions.

The research created the extreme models using a mix of real-world events, computer simulations and scientific theory. The scenarios omit international cascading effects including the agricultural collapse and resource wars.

The research was requested as part of a government’s climate resilience programme. Previous assessments have stated that insufficient focus was being allocated to low‐likelihood but high‐impact risks.

The government's climate advisors has recommended that the UK must "prepare for two degrees of warming" and evaluate the dangers for four degrees. Past policy documents have been labeled being "insufficient" by certain experts.

A national response commented: "The climate emergency is at the center of the country's focus, both building resilience and establishing itself as a low-carbon economy. It is crucial that the UK is resilient for the effects."