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The gravest possible consequences of the climate emergency for the UK have been outlined by scientists, encompassing a scorching 4C jump in temperatures to a two-metre increase in sea level. A separate possibility predicts a drop of 6C in temperature following the failure of critical Atlantic Ocean currents, which would massively disrupt farming and power requirements.

Possible Outcomes, Not Guarantees

These consequences, a number of which are linked to critical climate thresholds, are viewed as unlikely but possible. The researchers stated that these scenarios plugged a hole in planning that had left the UK unprepared for worst-case results.

"The climate extremes we have mapped aren’t predictions, but they are plausible," commented the lead researcher who directed the research. "The nation has been making preparations without the tools to assess catastrophic outcomes. We've now supplied planners what they need to plan for environmental results they pray never occur, but can’t afford to ignore."

A Suite of Severe Conditions Projections

A further series of worst-case scenarios maps the possible scale of severe conditions between now and the end of the century. These suggest that thermometer readings could rocket in particular seasons by up to 6C higher than historical levels, while rainfall could be triple standard measurements.

The likelihood of the extreme scenarios coming to pass cannot be precisely determined due to unknown factors about what measures will be enacted to combat climate change and how the planet's climate will behave. This analysis was likened to security threat evaluations or resilience checks for the banking sector.

Key Possibility Elements

• Four-Degree Warming: Global temperatures rising well above 4C by 2100 could transpire if international cooperation breaks down or if powerful amplifying effects including the Amazon rainforest dying emit its vast reserves of carbon. This would cause intense and enduring heat domes and dry spells hitting the UK in summer.
• AMOC Shutdown: A major ocean current, the Atlantic meridional overturning circulation (Amoc), is weakening and becoming unstable due to global heating. A collapse commencing by 2030 would lead to a drastic cooling in the UK. "Agriculture would struggle enormously and water supplies would be completely altered," noted the professor.
• Sudden Ocean Inundation: A surge of 2.0-2.2 metres around the UK by 2100 could take place if polar ice in Greenland and Antarctica melt abruptly, submerging low-lying areas. In contrast to the other scenarios, this risk is already recognized by infrastructure experts.
• Pollution Paradox: Temperatures could also be increased by about 0.75C if airborne particulates is sharply cut. 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 building of major projects, for example new towns, power generation facilities and water management networks. Awareness of these future hazards could also speed the push to slash greenhouse gas emissions.

The research created the worst-case scenarios using a blend of observed and historical experience, digital projections and established principles. The possibilities do not take into account international cascading effects like the devastation of food supplies and geopolitical instability.

The research was commissioned as part of a national adaptation planning initiative. Independent analyses have cautioned that not enough attention was being given to low‐likelihood but high‐impact risks.

The government's climate advisors has stated that the UK needs to "prepare for two degrees of warming" and examine the dangers for severe warming. Earlier government strategies have been described as being "very weak" by environmental groups.

A government spokesperson said: "Climate change is at the heart of this government’s agenda, both building resilience and establishing itself as a renewable energy leader. It is essential that the UK is prepared for the impacts."