TL;DR
Scientists have raised concerns about the stability of the Atlantic Meridional Overturning Circulation (AMOC). This article explains what AMOC is, what a weakening or collapse would mean for the UK, and how it relates to energy and climate policy.
UK Finance | Money Guides
The Atlantic Meridional Overturning Circulation (AMOC) is a large-scale system of ocean currents that transports warm surface water from the tropics northward into the North Atlantic, and returns cooler, saltier water southward at depth. It plays a critical role in regulating climate across the North Atlantic region, including the UK, and is a component of what is commonly referred to as the Gulf Stream system.
What AMOC Does for UK Climate
AMOC has a significant moderating effect on UK temperatures. Without it, the UK's climate would be substantially colder, particularly in winter months. The Met Office estimates that AMOC contributes several degrees Celsius of warming to northwestern European temperatures compared to what would be expected at equivalent latitudes without the current system.
AMOC also influences precipitation patterns, storm tracks across the North Atlantic, and sea level on the eastern seaboard of the United States and in parts of northwest Europe. Changes to AMOC strength can therefore affect flooding risk, agricultural productivity, and energy demand patterns in the UK.
What the Science Shows
The IPCC Sixth Assessment Report (AR6), published in 2021, assessed that AMOC will very likely weaken over the 21st century under all emissions scenarios, but that an abrupt collapse or a transition to a fundamentally different state is considered unlikely before 2100. The confidence in this assessment is medium, reflecting genuine scientific uncertainty about the tipping dynamics involved.
Research published since AR6 has raised concerns that AMOC may be closer to a tipping point than previously estimated. A 2023 paper in Nature Communications identified early warning signals in sea surface temperature data consistent with a system approaching instability. However, these findings are contested within the scientific community, and their implications for near-term risk are not yet incorporated into IPCC assessments.
Implications for UK Energy
UK energy demand is strongly seasonal, with gas consumption for heating representing the largest source of demand variation between summer and winter. A sustained cooling of UK temperatures as a result of AMOC weakening would increase heating demand, with implications for gas storage requirements, infrastructure capacity, and household energy costs. Ofgem's stress testing scenarios include cold weather events as a key planning assumption.
At the same time, cooling temperatures could reduce the efficiency of air source heat pumps, which are central to UK domestic decarbonisation strategy. Heat pump coefficient of performance declines as ambient temperatures fall, meaning that a colder baseline climate would require either larger heat pump installations or supplementary heating capacity.
Policy Context
The UK Climate Change Risk Assessment (CCRA), produced every five years under the Climate Change Act 2008, identifies ocean circulation changes as one of the risks requiring further research. The third CCRA (2022) noted that the risk of AMOC disruption was a priority risk area for the UK given the significant consequences of even a partial weakening.
The UK Government's Net Zero Strategy and the Climate Change Committee's advice both proceed on the basis of current climate projections from the Met Office UK Climate Projections (UKCP18), which do not incorporate a scenario of abrupt AMOC collapse. If scientific understanding evolves, these projections and associated adaptation plans would require revision.
What This Means Now
There is no current evidence of imminent AMOC collapse. Scientific consensus supports the view that AMOC will weaken gradually over coming decades, with the rate of weakening dependent on the trajectory of global greenhouse gas emissions. Rapid and sustained emissions reduction remains the most effective means of reducing the risk of exceeding AMOC tipping thresholds.
Frequently Asked Questions
What is AMOC?
The Atlantic Meridional Overturning Circulation (AMOC) is a system of ocean currents that transports warm water northward into the North Atlantic and is a key driver of UK climate, keeping temperatures significantly warmer than they would otherwise be.
Is AMOC about to collapse?
The IPCC assessed in its Sixth Assessment Report that an abrupt AMOC collapse before 2100 is unlikely but cannot be ruled out. Research since 2021 has raised questions about tipping point proximity, but scientific consensus does not support imminent collapse.
How would a weakened AMOC affect UK energy bills?
Colder baseline temperatures would increase heating demand, raise gas consumption, and potentially reduce the efficiency of heat pumps. This would have implications for energy system planning, storage requirements, and household energy costs.
