Photo: Krzysztof Hepner/Unsplash
Last month, the APPG for Climate, Nature & Security published Before the Border, the report of its inquiry into climate change as a driver of migration. We were pleased to see that SCRI’s written evidence was featured prominently. Our submission made an argument rarely made in this debate: that the country concerned about inward migration could itself become a country people leave.
There are many problems with the traditional frame of climate migration used in the UK and other rich nations, whereby migration from abroad destabilises the domestic situation. Most notably, there is tenuous evidence supporting a causal pathway from climate change through forced migration abroad to domestic instability in the UK. Yet far less explored is the risk that the UK itself could become subject to both internal and outbound migration pressures. These are often inadequately accounted for in national security assessments and strategies. Our submission focused on that risk.
The presumption of shelter is shakier than it seems
There is a presumption in countries such as the UK that we are sheltered from the more severe security impacts of climate change, and will continue to grapple only with our status as a place more vulnerable populations seek to migrate to. In some ways, this is correct. Global South countries are disproportionately exposed and vulnerable to current impacts and future risks. Yet the UK presumption of safety is cast into doubt when considering how cascading impacts are already manifesting, and that these dynamics are likely to escalate rapidly and severely into the future.
The sharpest illustration can be seen in the Atlantic ocean currents. The Atlantic Meridional Overturning Circulation (AMOC) and a sub-system, deep convection in the North Atlantic Sub-Polar Gyre (SPG), are fundamental to the UK having a temperate climate despite its high latitude. Both have been identified as having tipping points, capable of being pushed into runaway collapse.
While the uncertainties are significant, the latest research estimates an AMOC slowdown of around 50% by 2100. This could result from a trajectory of irreversible collapse, which could have started by 2063 under an intermediate emissions scenario. Indeed, it cannot be ruled out that a collapse process has already started. Similarly, while the chances of SPG collapse are also uncertain, SCRI has previously noted that there is up to a 45 per cent chance of an SPG collapse occurring this century, occurring potentially as early as 2040 and unfolding far more rapidly than AMOC collapse.
The UK could face extreme impacts
The impacts on the UK of these changes would be significant if not catastrophic. Our weather could see increased volatility and temperature swings, the possibility of unprecedented cold extremes, for example pushing towards -20°C in London during severe winter events and -30°C in Edinburgh, Arctic sea ice extending to Norfolk, and drier and more stormy conditions.
Our society is not structured to be resilient to such extremes. The UK’s homes and buildings are among the least energy efficient in Europe. It is plausible that many would not be able to withstand the temperature extremes of an AMOC collapse and would not be functional in their current form. The electricity grid would face surging demand from heating while simultaneously losing generation capacity due to extreme changes in weather conditions beyond operational ranges, and the current energy system has no contingency for a step-change of this scale. And an AMOC collapse has the potential to largely wipe out arable farming as an economically productive activity in the UK due to colder and drier conditions. Crops provide over two thirds of the UK population’s calories, so the large-scale loss of domestic crop growing would profoundly damage the UK’s food supply.
Meanwhile, domestic impacts would be coupled with huge global instability. Global monsoon systems which half the world’s population depend on for water and agriculture would be significantly disrupted, and land suitable for growing wheat and maize would fall by over 50% when combined with 2.5°C of global warming — including severe reductions in key UK food import markets such as Europe.
Impacts of AMOC collapse at both domestic and global levels would interact, multiplying and spreading destabilisation through financial instability, food system breakdown, severe trade disruption, forced displacement, public health threats, social incohesion, geopolitical competition, and political polarisation.
In turn, these impacts could plausibly drive migration internal to and outbound from the UK. With research projecting that temperature extremes in Edinburgh could reach almost -30°C, and that the city could spend over 20% of the year in freezing subzero temperatures, significant southbound internal migration appears plausible. Moreover, if domestic arable farming has been progressively rendered unviable and critical national infrastructure is failing, then many UK residents could seek to leave the country altogether. In a world of AMOC collapse, British people could become climate refugees.
It does not take a tipping point
It should be emphasised that it is not only catastrophic tipping points such as an AMOC collapse which could drive migration within and from the UK. Also relevant are the systemic, compounding and cascading shocks from climate hazards, which can propagate through systems such as international trade and finance. The UK is an open and highly import-dependent country. Even without the very worst impacts being triggered at the Earth system level, it cannot be ruled out that cascading systemic effects — especially should they compound one another — could undermine UK security sufficiently to force displacement of parts of the population.
Two things follow. These threats are not just a long-term problem: while the prospect of UK citizens themselves being driven to migration may appear far-fetched in the present moment, this situation could change rapidly and non-linearly in the near future. And the ability to manage it could be constrained, as the drivers of migration could also be eroding government capacity — financial instability, infrastructure malfunction, trade disruption. Climate impacts have the potential to undermine our ability to respond to them effectively.
Preparedness demands action now
The government should improve climate risk assessments to capture worst-case outcomes, including tipping points and cascading impacts within the UK itself. It should elevate these beyond the climate policy niche into core national security architecture. Physical early warning — such as ARIA’s welcome investment in detecting shifts in the Atlantic system — should be paired with equivalent capacity to anticipate socioeconomic consequences.
Rapid emissions reductions remain foundational, but the government should also pursue a broader conception of adaptation that strengthens the systems underpinning security in the places people live, and develop plans that explore how migration could be a productive adaptive tool. Systematic scenario exercising should be used to identify no-regrets investments that are useful to make in any scenario of the future. And the UK should pursue joint threat assessment and resilience planning with regional partners, including on AMOC risk with Nordic governments, who are increasingly concerned about this threat.
The APPG took the argument up directly, devoting a section of the report to UK exposure and cascading risk. It noted SCRI’s submission “makes an important contribution by inverting the standard perspective whereby the UK is most commonly framed as a potential receiving state for climate-linked movement originating elsewhere.”
We, and our colleagues at the APPG, note that the above scenarios are not a prediction that significant numbers of Britons will become climate refugees in the near term. Instead, they are an argument that national security planning must include plausible high-impact scenarios in which the systems currently allowing people to remain safely in place are disrupted in ways that planning assumptions do not currently accommodate.
Read the full report: Before the Border: Climate Migration & UK National Security. All-Party Parliamentary Group for Climate, Nature & Security Inquiry Report 2026.
It's so important that scenarios / possibilities such as the consequences of migratory collapse are, as a minimum, on the pattern recognition radar of all public sector leaders, teachers and those managing listed companies and corporations for shareholder benefit. Despite the significant increase in media coverage of AMOC, most folk that I talk to in health and regional leadership have little to no appreciation of the disruption that it could trigger. Thank you for the boldness and uncompromising insight that SCRI brings to the table.
Thanks for a great overview, New Climate Reality, on how late century could see extreme temperature swings in the UK. But let's not lose focus that climate scientist James Hansen has recently stated that global surface temperature is already at 1.5 degrees C above preindustrial levels and he predicted we'll see 1.7 degrees C in 2027 partly due to El Nino and perhaps we'll hit 2.0 degrees C by mid to late 1930s. It's not your great-great grandchildren that are at risk of famine, it's your children who currently are in the first half of their expected lifespans.