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The direst projected effects of the climate emergency for the UK have been mapped by researchers, ranging from a scorching 4C increase in temperatures to a two-metre surge in ocean levels. An alternative projection foresees a plunge of 6C in temperatures following the collapse of key Atlantic Ocean currents, which would profoundly upset agriculture and energy needs.

Plausible Outcomes, Not Forecasts

These consequences, some of which are connected to critical climate thresholds, are seen as low probability but plausible. The scientists explained that these models addressed a shortfall in forecasting that had left the UK not ready for worst-case results.

"The worst-case scenarios we have mapped aren’t predictions, but they are credible," stated Nigel Arnell who directed the study. "The UK has been formulating policy without the tools to test against extreme possibilities. We've now provided planners what they need to plan for future conditions they wish to avoid, but dare not dismiss."

A Suite of Harsh Climate Possibilities

A further series of severe models maps the potential extent of severe conditions between now and the year 2100. These suggest that thermometer readings could rocket in particular seasons by up to 6C higher than historical levels, while precipitation could be triple standard measurements.

The probability of the extreme scenarios occurring remains uncertain due to a lack of certainty about what action will be taken to combat global heating and how the climate system will react. This analysis was compared to national security risk assessments or resilience checks for financial systems.

Critical Outcome Details

• Four-Degree Warming: Worldwide averages soaring past 4C by 2100 could happen if emissions cuts collapses or if strong feedback loops like the Amazon basin dying unleash its huge repository of carbon. This would cause extreme and prolonged heat domes and dry spells hitting the UK in summer.
• Atlantic Current Collapse: A major ocean current, the North Atlantic current, is weakening and showing signs of collapse due to global heating. A complete failure beginning in 2030 would lead to a six-degree temperature drop in the UK. "Crop production would face immense difficulties and water resources would be completely altered," explained Arnell.
• Sudden Ocean Inundation: A surge of 2.0-2.2 metres around the UK by 2100 could happen if glaciers in the polar regions disintegrate quickly, inundating coastal cities and towns. Unlike the other scenarios, this risk is already understood by coastal engineers.
• Clean Air Warming: Temperatures could also be increased by about 0.75C if industrial aerosols is drastically reduced. This unexpected result occurs because tiny specks from industrial activity block solar radiation from reaching the ground.

Planning for the Extreme

The severe models could be applied to guide the building of critical national infrastructure, such as expanded cities, energy plants and urban drainage systems. Knowledge about these climate risks could also accelerate the drive to cut carbon pollution.

The research formulated the extreme models using a combination of observed and historical experience, climate models and climate physics. The possibilities do not take into account international cascading effects like the devastation of food supplies and resource wars.

The project was commissioned as part of a national adaptation planning initiative. Independent analyses have warned that not enough attention was being given to catastrophic yet improbable risks.

An independent advisory body has recommended that the UK needs to "adapt to 2C" and examine the threats for severe warming. Earlier government strategies have been described as being "insufficient" by some observers.

An official statement commented: "Climate change is at the center of our national priorities, both adapting for the future and transitioning to a low-carbon economy. It is essential that the UK is ready for the impacts."