British scientists have issued a stark warning, revealing a series of worst-case climate scenarios for the UK that the government must now prepare for. The analysis, which fills a critical gap in national planning, outlines plausible futures including a scorching 4C rise in average temperatures and a devastating 2-metre rise in sea levels by the end of the century.
Plausible Extremes: From Scorching Heat to Ocean Collapse
The research, led by Professor Nigel Arnell from the University of Reading and published in the journal Earth's Future, is not a prediction but a stress test for the nation. It combines historical data, computer simulations, and climate theory to map out low-probability but high-impact risks that have previously been overlooked.
A global temperature rise well above 4C by 2100 is one alarming scenario. This could occur if international climate action collapses or if critical tipping points are triggered, such as the die-back of the Amazon rainforest releasing vast carbon stores. For the UK, this would mean extreme, prolonged summer heatwaves and droughts, far surpassing the deadly events already seen with just a 1.3C global increase.
Paradoxically, a rapid cut in industrial air pollution could also drive UK temperatures up by around 0.75C, as it would remove sun-blocking aerosol particles from the atmosphere.
Perhaps the most disruptive scenario involves the Atlantic Ocean. The Atlantic meridional overturning circulation (Amoc), a crucial current system, is weakening due to global heating. Its total collapse, beginning as early as 2030, could plunge UK temperatures by a staggering 6C. "Agriculture would struggle enormously and water resources would be completely altered," warned Professor Arnell. "Our heat and energy system would be completely caught out... It would be massively disruptive."
Coastal Flooding and Torrential Rain
The analysis also details a potential 2.0 to 2.2 metre rise in sea levels around the UK coast by 2100, if glaciers in Greenland and Antarctica undergo rapid collapse. This would flood numerous coastal cities and towns, a threat already on the radar of planners.
Furthermore, the study sets out the potential intensity of future extreme weather. It indicates that monthly temperatures could soar up to 6C above average, while rainfall in some periods could be triple the normal levels, leading to severe flooding.
A Call for Preparedness and Stronger Adaptation
Commissioned by the Met Office for the government's climate resilience programme, the research aims to provide the tools for long-term infrastructure planning—from new towns and nuclear power stations to urban drainage—ensuring they can withstand these extreme outcomes.
Professor Arnell compared the analysis to national security risk assessments or the Bank of England's financial stress tests. "You couldn't have known what the probability of Russia invading Ukraine was, but you could have said this is what the consequences might be," he stated, emphasising the need to prepare for plausible shocks.
The report arrives amid criticism of the UK's current adaptation plans, labelled "very weak" by some. The independent Climate Change Committee (CCC) has advised that the nation must "adapt to 2C and assess the risks for 4C". In response, a government spokesperson highlighted a record £10.5bn investment in new flood defences and plans for nine new reservoirs.
The government has requested an evidence review of climate risks from the CCC, due in spring, and guidance on which climate scenarios to use in national planning. The scientists conclude that understanding these severe risks should accelerate the urgent transition away from fossil fuels.
