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The most severe possible consequences of the climate crisis for the UK have been mapped by researchers, including a blistering 4C jump in mean temperatures to a 6.5-foot increase in ocean levels. A separate possibility predicts a decline of 6C in temperatures following the shutdown of crucial Atlantic Ocean currents, which would severely impact farming and energy needs.

Credible Events, Not Forecasts

These impacts, a number of which are linked to climate tipping points, are seen as unlikely but possible. The team explained that these scenarios addressed a shortfall in risk assessment that had left the UK not ready for catastrophic possibilities.

"The severe weather events we have detailed should not be seen as certainties, but they are credible," stated Nigel Arnell who oversaw the research. "Britain has been planning without the frameworks to plan for catastrophic outcomes. We've now supplied policymakers what they need to get ready for climate outcomes they pray never occur, but dare not dismiss."

A Suite of Severe Conditions Projections

A further series of severe models sets out the potential extent of harsh climate between now and the close of the 2100s. These show that temperatures could rocket in some months by up to 6C above average, while rainfall could be triple typical amounts.

The likelihood of the worst-case outcomes occurring could not be calculated due to unknown factors about what steps will be implemented to tackle global heating and how the climate system will react. This analysis was likened to defence planning or scenario planning for the banking sector.

Major Possibility Details

• Severe Heating: Planetary heating exceeding 4C by 2100 could transpire if emissions cuts collapses or if powerful amplifying effects such as the Amazon basin dying emit its huge repository of carbon. This would cause severe and lengthy heat domes and water shortages hitting the UK in summer.
• Atlantic Current Collapse: A key circulation system, the Atlantic meridional overturning circulation (Amoc), is slowing down and showing signs of collapse due to climate change. A complete failure commencing by 2030 would lead to a 6C cooling in the UK. "Crop production would face immense difficulties and freshwater availability would be completely altered," noted the professor.
• Accelerated Coastal Flooding: A surge of 2.0-2.2 metres around the UK by 2100 could take place if polar ice in the Arctic and Antarctic melt abruptly, flooding coastal cities and towns. In contrast to the other scenarios, this possibility is already recognized by infrastructure experts.
• Clean Air Warming: Global averages could also be increased by about 0.75C if industrial aerosols is sharply cut. This paradoxical outcome occurs because aerosol particles from burning coal block sunlight from reaching the ground.

Preparing for the Extreme

The severe models could be used to inform the development of major projects, such as housing developments, power generation facilities and water management networks. Knowledge about these climate risks could also hasten the push to cut fossil fuel emissions.

The analysis developed the extreme models using a mix of past data and records, computer simulations and established principles. These outcomes omit broader worldwide issues including the global food shortages and resource wars.

The research was requested as part of a national adaptation planning initiative. Previous assessments have stated that insufficient focus was being given to high-consequence, low-probability risks.

Official experts has recommended that the UK must "prepare for two degrees of warming" and evaluate the threats for four degrees. Previous adaptation plans have been described as being "insufficient" by environmental groups.

An official statement commented: "Climate change is at the heart of our national priorities, both building resilience and becoming a clean energy superpower. It is vital that the UK is resilient for the impacts."