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The direst possible consequences of the climate crisis for the UK have been outlined by experts, encompassing a searing 4C rise in temperatures to a two-metre surge in sea levels. A separate possibility envisions a drop of 6C in temperatures following the shutdown of key Atlantic Ocean currents, which would severely impact agriculture and energy needs.

Plausible Extremes, Not Guarantees

These impacts, some of which are associated with critical climate thresholds, are considered as unlikely but credible. The researchers explained that these projections plugged a hole in forecasting that had rendered the UK not ready for worst-case results.

"The worst-case scenarios we have outlined are not forecasts, but they are credible," commented the lead researcher who oversaw the analysis. "The nation has been making preparations without the frameworks to assess worst-case scenarios. We've now supplied decision-makers what they need to plan for future conditions they wish to avoid, but must not overlook."

A Range of Severe Conditions Projections

Another collection of severe models sets out the potential extent of harsh climate between now and the year 2100. These suggest that thermometer readings could skyrocket in certain periods by up to 6C higher than the norm, while precipitation could be three times typical amounts.

The chance of the extreme scenarios occurring cannot be precisely determined due to uncertainty about what action will be taken to address global heating and how the climate system will react. This research was described as similar to security threat evaluations or resilience checks for the banking sector.

Critical Scenario Highlights

• Four-Degree Warming: Global temperatures soaring past 4C by 2100 could transpire if international cooperation fails or if vicious cycles such as the tropical forests perishing unleash its huge repository of carbon. This would result in extreme and prolonged heatwaves and dry spells affecting the UK in summer.
• AMOC Shutdown: A critical sea current, the Atlantic meridional overturning circulation (Amoc), is weakening and showing signs of collapse due to global heating. A full shutdown beginning in 2030 would lead to a drastic cooling in the UK. "Farming would struggle enormously and freshwater availability would be drastically changed," explained the professor.
• Sudden Ocean Inundation: A surge of 2.0-2.2 metres around the UK by 2100 could take place if ice sheets in Greenland and Antarctica melt abruptly, submerging seaside communities. In contrast to the other scenarios, this risk is already understood by planners.
• Clean Air Warming: Global averages could also be pushed higher by about 0.75C if pollution from industry is rapidly cleaned up. This paradoxical outcome occurs because aerosol particles from fossil fuel combustion block solar radiation from reaching the ground.

Building Resilience Against the Unthinkable

These dire projections could be applied to guide the construction of major projects, for example expanded cities, nuclear power stations and flood defences. Awareness of these climate risks could also hasten the drive to slash greenhouse gas emissions.

The analysis formulated the severe projections using a mix of observed and historical experience, climate models and scientific theory. The possibilities do not take into account broader worldwide issues such as the agricultural collapse and increased conflict.

The project was initiated as part of a official adaptation planning initiative. Earlier reports have stated that too little consideration was being given to high-consequence, low-probability risks.

Official experts has recommended that the UK must "adapt to 2C" and assess the dangers for four degrees. Previous adaptation plans have been labeled being "insufficient" by environmental groups.

An official statement said: "The climate emergency is at the heart of this government’s agenda, both building resilience and establishing itself as a low-carbon economy. It is essential that the UK is resilient for the impacts."