“A possible collapse today will most likely be different from previous tipping…”: Dr. Susanne Ditlevsen on AMOC

Susanne Ditlevsen is President of the Royal Danish Academy of Science and Letters. She is Professor of statistics and stochastic models in biology at University of Copenhagen. Together with her brother Peter Ditlevsen this team of two have done some remarkable work on the Atlantic Meridional Overturning Circulation (AMOC) – a critical Earth system that could tip if we do not urgently bring human induced emissions under check.

The tipping could have far reaching consequences across the planet. We do not have the luxury of the timeline IPCC suggests – which goes into 2100. The Ditlevsen work indicates it could happen as early as 2037. Iceland is the only country which is treating it as an emergency.

“I think we should still work hard for reducing greenhouse gas emissions”, believes Susanne. She appeals for designing a resilient society. “This problem is so complex that we need to attack it from many different angles”. Global cooperation is her mantra.

Praveen Gupta (PG): Your insights into how soon might the AMOC tip?

Susanne Ditlevsen (SD): I believe there is a non-negligible risk that it might happen/start in this century – given the severe consequences, this risk should be taken very seriously.

PG: AMOC has had a history of tipping. Does a predominant anthropocentric trigger make the manifestation any different?

SD: A possible collapse today will most likely be different from previous tipping because of global warming. We know little about how global warming will interact with a collapse, for that we rely on large climate models.

“Research groups have different expertise, and we should all contribute with what we can”

PG: Fundamental difference between your and IPCC’s methodologies?

SD: IPCC summarizes the existing knowledge in the scientific literature, in that sense one cannot compare methodologies as such. The current research on the AMOC is conducted by many independent groups and uses many different methodologies and data sets – as it should be. This problem is so complex that we need to attack it from many different angles. Each method will have its pros and cons, and uncertainties will be different. We need to conclude on the basis of all the evidence we have. Research groups have different expertise, and we should all contribute with what we can.

PG: Does CO2 emission tend to get higher attribution vis-à-vis biodiversity loss and pollution?

SD: CO2 emissions is pollution of the atmosphere and leads to global warming. Biodiversity loss will happen in certain places due to global warming and changes habitat conditions, in other places it will not necessarily decrease biodiversity, but change the ecosystems (for example are many new whale species spending time in East Greenland, while endemic species are under pressure).

“I believe it is more straightforward, cheaper and safer to reduce emissions”

PG: Do you see any scope for mitigation, or have we run out of time for that?

SD: I think we should still work hard for reducing greenhouse gas emissions.

PG: Likewise, could adaptation do any good?

SD: One good thing would be to design our societies more resilient, for example, stop constructions of new building in areas that are exposed to flooding.

PG: Would we require some stop gap relief to pre-empt AMOC from tipping? Could that come from geo-engineering (SRM)? Damming of Bering Strait?

SD: I would not rely on geoengineering. First, we might not know exactly how to do it, nor understand completely about side effects. Second, we bind ourselves to continue for many generations to come. What if such geoengineering suddenly breaks down, say, 100 years from now? Then there might be a much quicker and more severe change. I believe it is more straightforward, cheaper and safer to reduce emissions, and this is much more fair to the common generations that will not be forced to continue some geoengineering they did not choose.

PG: Many thanks, Dr. Ditlevsen. Look forward to following your pathbreaking work in this space. We have reached a point where BAU is just not sustainable.