Iceland has declared the AMOC a national security threat and an existential risk in the coming decades, enabling its Government to prepare for worst-case scenarios. Should we be worried?
Where the public conversation becomes dangerously narrow is in the proposed response. The typical conclusion is that the only way to prevent AMOC collapse is through rapid emissions cuts.
That’s essential — but it is not enough.
Emissions reduction works, but slowly. Even an aggressive decarbonization effort will not meaningfully cool the North Atlantic or slow Greenland’s meltwater discharge within the next twenty to thirty years. The AMOC, however, is responding to current heat and freshwater imbalances. We cannot rely on long-term tools alone to stabilize a system that may tip within decades.
If AMOC collapse is a national security risk — and it is — we need a broader response.
There are additional ways to reduce AMOC risk that deserve immediate research and serious public discussion.
Marine Cloud Brightening (MCB) is one of the most promising. By spraying fine sea-salt particles into marine clouds, MCB increases reflectivity and cools ocean surface waters. Unlike stratospheric aerosol injection, it is regional and adjustable. Applied over the subpolar North Atlantic, it could cool the critical region where AMOC deep-water formation is weakening, strengthen density contrasts, and even slow Greenland melt.
Greenland and Arctic ice-shielding is another option. Reflective covers, winter seawater pumping, fjord shading, and ice-mélange stabilization could reduce the freshwater plume that is destabilizing the AMOC. Every tonne of meltwater kept out of the Labrador and Nordic Seas reduces risk.
Targeted downwelling support, not global ocean manipulation, could help break the freshwater “lid” that now prevents winter convection in parts of the subpolar gyre. Localised ocean-mixing systems may restore the sinking that drives the AMOC.
Stratospheric Aerosol Injection (SAI) is powerful but high-risk — not the only hope, but potentially part of a carefully governed portfolio only to be seriously considered when all other options have failed (for which we are running out of time as our window for climate cooling is closing). A Northern Hemisphere-weighted SAI deployment could cool the Arctic and slow cryosphere loss. But this approach demands global agreement, caution, and contingency planning as well as broad political alignment.
Finally, carbon removal remains essential for long-term stabilization but is too slow to alter near-term tipping risk on its own.
The correct framing is not “mitigation or geoengineering.”
It is risk-risk management — the same logic used in national defence, public health, and disaster planning. Doing nothing new carries risks. Expanding our toolbox carries different risks. The responsible path is to evaluate all options, transparently and scientifically.
We cannot negotiate with the melting point of ice.
But we can choose whether to engage every available tool to keep the AMOC — and the societies it stabilizes — from crossing a point of no return.
Oxford (2024): Addressing the urgent need for direct climate cooling: Rationale and options
Hi Sander, my interests lie in putting water back into the ground (rather than runoff), improving soils filter capacity and fertility to improve groundwater/surface water quality, and adoption of technologies to make our wastewater and solid waste management system better.
I know that the earth is a complex system and the combustion of fossil fuels is has a lot to do with the problem. But now that they are finally talking about f-gas emissions and the great biosolids problem in the news, and now that there is a quite a bit of research focused on agricultural-practices being a potential huge source of greenhouse gases (eg. Biochar journal):
Do you think that we have a better shot at meeting our goals?
HI tom, it is interesting due to the differing speeds of the two types of water transport ocean and air that the anomaly in 2008-2010 may have been due in part to the larger fresh water rainfall input from the evaporation and therefore saltier current further to the south. This seems to have altered overall concentrations on to a lower path. If this is the case then the notion that we could cloud seed in different areas of the ocean may offer another adjusting mechanism to put the timing divergence back into alignment. Great article and it has given me much to think about. many thanks
looking at the Saharan dust deposition, in 2008-10 were some of the biggest years this then triggered the great sargassum blooms which has been a phenomena since 2011, what is interesting is if one sees this as a nutrient accumulation that would usually be lost through bottom ocean deposition but now is sustained, this seems to mark the trigger point of inflection in the graph. This then may allow for a rainfall shift and may be an underlying trigger for this pattern shift. There is already proof of the link of dust and climatic changes
So maybe the solution lies in the greening of the Sahel and the Sahara instead of upper atmosphere aerosol injections. Can we also shift rainfall patterns using Iron deposition? as this would also help right the ocean imbalance we discussed in earlier articles.
Since much of the evaporation from the ocean leaves a saltier upper layer and the two masses work on differing time frames, Air days to weeks, and ocean months to years to cover the same distances then using the prevailing systems, the accumulated shift of one over the other could be enough to create a change one would think. Can we create shifts on such scale with positive and profitable side effects?
The Saharan dust deposition you describe is interesting. A weakening AMOC would affect the Sahel too as the Hadley circulation moves south, so there may be a great deal to gain from targeted iron fertilisation on this issue too.
Thank you for the great write up. I especially appreciated the explained graphs of some of the recent research. I have skimmed through most of those same papers, but lack the patience and background to always understand all the acronyms and what they mean.
A gigatonne is a billion tons . Greenland melt numbers need revision , hard to think in such big numbers. 37 billion tones of CO2 emissions , 200 billion tones of melting ice .
AMOC slowing has a profound negative effect on the Northern hemisphere ocean carbon sink and deep water ventilation.
Thanks Bruce, I just double checked the numbers and is 200 billion tonnes a year. Another way to visualise it is 2.5 million lites a second. Or 3 olympic swimming pools per second. Its astronomical.
The deep water ventilation and carbon sequestration are profound negative impacts.
There is another scenario for the AMOC collapse, other than the 50 years slow decline, and that is the current turns southward along the West African coast.
I understand that has been tracked in the seabed paleo records as occurring over a 3 year 'flip' period, and as it doesn't require the current to decline much more than it already has, that would seem to me to be the worst case scenario in the short term.
But it seems to have fallen off the agenda in terms of discussions and research. Any ideas why?
That's a good question. I would imagine that since most of the paleo evidence comes from the last glaciation, the current would have been moved south by the ice sheet that encroached all the way south to Ireland. The overturning would have moved with it, so driving the current to the southeast. The wind driven Gulf Stream may also have taken this track picking up on the strengthened jet stream caused by the more southerly ice sheet as well.
Or the other way around - the warm current turning southward allowed the ice to encroach as far south as Ireland, as it might well do again in the near future.
I suppose the real issue is we have triggered changes in AMOC and we don't have much idea what triggers which response. I suspect we'll be surprised when we all find out for sure, by which time it'll be way too late!
I, for one, have little respect for the decades of arrogantly confident predictions of IPCC that seem to have the fallback position that 'nothing significant will happen until 2100 at the earliest', which I suspect has been written by politicians and oil execs. All the subsequent science has been about shorter timescales and much more dire outcomes. I think the politicians need to get out of the way and let the scientists get on with it, without IPCC censorship.
That could well be the case. The complexities of the system are huge.
As for the IPCC, they have had to err on the side of caution. James Hansen calls it Scientific Reticence. Better to be surprised than wrong.
I tend to look at the detailed working group reports which have less interference. The summary for policy makers is agreed by country member lawyers during final editing so will always gravitate to lowered risks.
Where the public conversation becomes dangerously narrow is in the proposed response. The typical conclusion is that the only way to prevent AMOC collapse is through rapid emissions cuts.
That’s essential — but it is not enough.
Emissions reduction works, but slowly. Even an aggressive decarbonization effort will not meaningfully cool the North Atlantic or slow Greenland’s meltwater discharge within the next twenty to thirty years. The AMOC, however, is responding to current heat and freshwater imbalances. We cannot rely on long-term tools alone to stabilize a system that may tip within decades.
If AMOC collapse is a national security risk — and it is — we need a broader response.
There are additional ways to reduce AMOC risk that deserve immediate research and serious public discussion.
Marine Cloud Brightening (MCB) is one of the most promising. By spraying fine sea-salt particles into marine clouds, MCB increases reflectivity and cools ocean surface waters. Unlike stratospheric aerosol injection, it is regional and adjustable. Applied over the subpolar North Atlantic, it could cool the critical region where AMOC deep-water formation is weakening, strengthen density contrasts, and even slow Greenland melt.
Greenland and Arctic ice-shielding is another option. Reflective covers, winter seawater pumping, fjord shading, and ice-mélange stabilization could reduce the freshwater plume that is destabilizing the AMOC. Every tonne of meltwater kept out of the Labrador and Nordic Seas reduces risk.
Targeted downwelling support, not global ocean manipulation, could help break the freshwater “lid” that now prevents winter convection in parts of the subpolar gyre. Localised ocean-mixing systems may restore the sinking that drives the AMOC.
Stratospheric Aerosol Injection (SAI) is powerful but high-risk — not the only hope, but potentially part of a carefully governed portfolio only to be seriously considered when all other options have failed (for which we are running out of time as our window for climate cooling is closing). A Northern Hemisphere-weighted SAI deployment could cool the Arctic and slow cryosphere loss. But this approach demands global agreement, caution, and contingency planning as well as broad political alignment.
Finally, carbon removal remains essential for long-term stabilization but is too slow to alter near-term tipping risk on its own.
The correct framing is not “mitigation or geoengineering.”
It is risk-risk management — the same logic used in national defence, public health, and disaster planning. Doing nothing new carries risks. Expanding our toolbox carries different risks. The responsible path is to evaluate all options, transparently and scientifically.
We cannot negotiate with the melting point of ice.
But we can choose whether to engage every available tool to keep the AMOC — and the societies it stabilizes — from crossing a point of no return.
Oxford (2024): Addressing the urgent need for direct climate cooling: Rationale and options
https://academic.oup.com/oocc/article/4/1/kgae014/7731760
Thanks, I agree with you 100%
Hi Sander, my interests lie in putting water back into the ground (rather than runoff), improving soils filter capacity and fertility to improve groundwater/surface water quality, and adoption of technologies to make our wastewater and solid waste management system better.
I know that the earth is a complex system and the combustion of fossil fuels is has a lot to do with the problem. But now that they are finally talking about f-gas emissions and the great biosolids problem in the news, and now that there is a quite a bit of research focused on agricultural-practices being a potential huge source of greenhouse gases (eg. Biochar journal):
Do you think that we have a better shot at meeting our goals?
Its not just about CO2 and methane anymore right?
So good to hear someone point this out!
Brilliant Tom, just brilliant. Great writing on a very complex set of issues.
Thank you so much! I really appreciate it.
HI tom, it is interesting due to the differing speeds of the two types of water transport ocean and air that the anomaly in 2008-2010 may have been due in part to the larger fresh water rainfall input from the evaporation and therefore saltier current further to the south. This seems to have altered overall concentrations on to a lower path. If this is the case then the notion that we could cloud seed in different areas of the ocean may offer another adjusting mechanism to put the timing divergence back into alignment. Great article and it has given me much to think about. many thanks
looking at the Saharan dust deposition, in 2008-10 were some of the biggest years this then triggered the great sargassum blooms which has been a phenomena since 2011, what is interesting is if one sees this as a nutrient accumulation that would usually be lost through bottom ocean deposition but now is sustained, this seems to mark the trigger point of inflection in the graph. This then may allow for a rainfall shift and may be an underlying trigger for this pattern shift. There is already proof of the link of dust and climatic changes
https://www.science.org/doi/pdf/10.1126/sciadv.abe6102
So maybe the solution lies in the greening of the Sahel and the Sahara instead of upper atmosphere aerosol injections. Can we also shift rainfall patterns using Iron deposition? as this would also help right the ocean imbalance we discussed in earlier articles.
Since much of the evaporation from the ocean leaves a saltier upper layer and the two masses work on differing time frames, Air days to weeks, and ocean months to years to cover the same distances then using the prevailing systems, the accumulated shift of one over the other could be enough to create a change one would think. Can we create shifts on such scale with positive and profitable side effects?
Hi Theodore, Many thanks for your thoughts.
The Saharan dust deposition you describe is interesting. A weakening AMOC would affect the Sahel too as the Hadley circulation moves south, so there may be a great deal to gain from targeted iron fertilisation on this issue too.
Thank you for the great write up. I especially appreciated the explained graphs of some of the recent research. I have skimmed through most of those same papers, but lack the patience and background to always understand all the acronyms and what they mean.
Thank you.
A gigatonne is a billion tons . Greenland melt numbers need revision , hard to think in such big numbers. 37 billion tones of CO2 emissions , 200 billion tones of melting ice .
AMOC slowing has a profound negative effect on the Northern hemisphere ocean carbon sink and deep water ventilation.
Thanks
Thanks Bruce, I just double checked the numbers and is 200 billion tonnes a year. Another way to visualise it is 2.5 million lites a second. Or 3 olympic swimming pools per second. Its astronomical.
The deep water ventilation and carbon sequestration are profound negative impacts.
There is another scenario for the AMOC collapse, other than the 50 years slow decline, and that is the current turns southward along the West African coast.
I understand that has been tracked in the seabed paleo records as occurring over a 3 year 'flip' period, and as it doesn't require the current to decline much more than it already has, that would seem to me to be the worst case scenario in the short term.
But it seems to have fallen off the agenda in terms of discussions and research. Any ideas why?
That's a good question. I would imagine that since most of the paleo evidence comes from the last glaciation, the current would have been moved south by the ice sheet that encroached all the way south to Ireland. The overturning would have moved with it, so driving the current to the southeast. The wind driven Gulf Stream may also have taken this track picking up on the strengthened jet stream caused by the more southerly ice sheet as well.
That's just my guess though.
Or the other way around - the warm current turning southward allowed the ice to encroach as far south as Ireland, as it might well do again in the near future.
I suppose the real issue is we have triggered changes in AMOC and we don't have much idea what triggers which response. I suspect we'll be surprised when we all find out for sure, by which time it'll be way too late!
I, for one, have little respect for the decades of arrogantly confident predictions of IPCC that seem to have the fallback position that 'nothing significant will happen until 2100 at the earliest', which I suspect has been written by politicians and oil execs. All the subsequent science has been about shorter timescales and much more dire outcomes. I think the politicians need to get out of the way and let the scientists get on with it, without IPCC censorship.
Just my view.
That could well be the case. The complexities of the system are huge.
As for the IPCC, they have had to err on the side of caution. James Hansen calls it Scientific Reticence. Better to be surprised than wrong.
I tend to look at the detailed working group reports which have less interference. The summary for policy makers is agreed by country member lawyers during final editing so will always gravitate to lowered risks.