The most important climate change paper of 2022 you never heard of
What do we choose — 10m higher sea level or pulling CO2 out of the air?
The topic of climate tipping points has been a hot area of research in the last 10 years or so. This looks at what point will changes be set off by the increased levels of greenhouse gases in the atmosphere that are not reversible.
In September 2022 Armstrong McKay et al. published, in the highly esteemed journal Science, a major review of research on a range of climate system tipping points, including the melting of Greenland and West Antarctic ice sheets — major contributors to global sea level rise.°
https://www.science.org/doi/10.1126/science.abn7950
It sets out the global warming levels at which a variety of climate system tipping points might be set off.
Figure 2, above, is the important one in the paper. On the left hand axis is the global warming level. We are currently at ~1.2 °C on this axis.
Now remember that the current Paris Agreement target of staying under 2°C is approximately what happens under the often used target of “net zero by 2050”. In reality, we need to be pulling down some CO2 out of the atmosphere to meet that 2°C target, not just “net zero emissions”.
In that figure, that 2°C target likely sets off the Greenland and West Antarctic ice sheets, and the tropical coral reef tipping points, the Barents Sea tipping point, the boreal permafrost Arctic tipping point, and raises the possibility of starting the Labrador Sea and glacier tipping points.
So what do those tipping points mean? If I had a criticism of this paper, it is that they don’t really spell out the implications of what each of those tipping points mean, which is possibly why the import of it was lost and it didn’t get the headlines it deserved.
Greenland has ~7m total of sea level locked up in the ice sheets on it. Research has suggested for a few years now that ~5m of that is vulnerable to the levels of warming we are looking at happening. In the paper they point out that the ice on Greenland formed when CO2 levels were below 300ppm.
West Antarctic ice sheets, mainly Thwaites Glacier and the Pine Island Glacier or PIG, would release about 3.5m in global sea level rise when they tip over. When that might happen is another hot topic in climate science, and there is a lot of research suggesting they may already be undercut by warming Southern Ocean water enough to at least partly initiate their collapse, and the associated irreversible sea level rise.
So lets do some sums…5m +3.5m+0.25m from melting glaciers and ~0.8m from thermal expansion of the oceans in a 2° C warmer world = ~10m total sea level rise.
This is not an instantaneous response… but they are irreversible tipping points once initiated. Time frames for the collapse and melting of these ice sheets are given in the paper. Think of moving a block of ice from your freezer into the fridge compartment. The block takes a while to melt, but you know it will absolutely turn into a puddle of water in the slightly warmer temperatures. So these ice sheets take many hundreds to a thousand years or more to fully melt. But significant parts can collapse over shorter time frames, so 1–2 meters higher sea level in the next hundred years or so is a real possibility.
The Arctic Boreal permafrost melt is another important tipping point. The currently frozen ground in the Arctic could produce enough CO2 and methane, if all the Arctic warmed up above freezing, equal to double the CO2 that is currently in the atmosphere — that would be a worry. But research suggests that all happening is unlikely, but amounts equal to ~10% of current human emissions may be started from this tipping point over coming decades. So while we are trying to eliminate emissions, we would have a feedback in the natural climate system making that job harder.
So where does this leave us as far as climate policy?
It means that choosing to try to hit the 2°C target has ~10m of sea level rise associated with it for us and our descendants to deal with.
That obviously has hundreds and hundreds of trillions of dollars of costs associated with managing movement of populations as major cities gradually get inundated and coasts massively erode over coming centuries.
I had to look up what came after millions, billions, trillions…the word quadrillions of dollars would become rooted in the new vocabulary of the climate changed world.
So can we stay at the 1.5°C which we need to do to (hopefully) avoid initiating 10m of sea level rise? Well we are (still) rapidly chewing through the emissions budget which would keep warming to that level. The IPCC stated at current emissions levels that the emissions budget to stay at or below 1.5° C warming runs out by around 2030. Or we could engage in a stronger emissions reduction pathway than the 2°C Paris Agreement target, by acting more strongly from now and get to net zero emissions by ~2035 to 2040 and that might still meet that 1.5°C target.
Are we likely to do that? I would like to have expected that the paper inspired a major rethink of international and governmental policy that inspired stronger action on emissions. That the paper did not do that is a major failure of science journalism. Science journalists everywhere need a major kick up the ass for letting this one slip past them.
The paper hints at another of our choices. The ~300ppm level at which the Greenland ice sheets formed.
If we can’t strongly reduce emissions to zero before 2050, our other option to avoid the 10m higher sea level is then to reduce the atmospheric radiative forcing from the higher CO2 levels, by sucking down CO2 out of the atmosphere and reducing methane emissions. That is the fancy scientific way of saying “ we need to turn the temperature knob in the fridge compartment down to a lower level”. The higher CO2 and methane levels are stopping heat from escaping to space more now with 410ppm CO2 than they did when CO2 levels were 350ppm or less.
Is direct air capture of CO2 from the atmosphere feasible? It is already being done but is expensive per tonne of CO2- Climeworks are selling robustly sequestered direct air capture CO2 at ~$1000US per tonne. I think over the next 20 years the cost will come down along similar curves to the way solar and wind prices have massively decreased, and it will be seen as the way to avoid those quadrillion dollar costs of sea level rise.
What would the return on that investment in direct air capture be? I did some rough back of the envelope estimates of the cost to reduce CO2 from say 420ppm to ~350ppm — Bill McKibbins 350.org has been a good estimate of where things should be for a while now — using $50 US per tonne of CO2. The total cost is ~$20 trillion total. The global economy generates about ~$90 trillion per year, and we unbelievably still give ~$6 trillion US per year to fossil fuel companies in subsidies — so this is feasible if CO2 capture can be made less expensive in the future, and even at $1000 US per tonne is probably still a positive return on investment.
And obviously, we cannot use direct air capture as a way of emitting more for longer now. Putting as little more in the atmosphere ahead of net zero so we don’t have to pay to remove it again later to avoid 10m higher sea level would be a really, really smart thing to do.
Who will pay will be the big question. I would suggest a retrospective carbon tax will be the way to go to pay for this, as well as reparations from fossil fuel companies who engaged in deception of the global community on the impacts of climate change — looking at you in particular Exxon Mobil, though you were not alone in this.
So there are our choices. I do not think it is doom and gloom. We can manage this — but it will be challenging. There will be lots of jobs out there doing what will be needed. And there is enough money to do it — the problem is most of it is currently sitting in the bank vaults of fossil fuel companies and billionaires.
POSTSCRIPT:
After Modeller responded in the comments to me about the idea of large scale direct air capture, I had to rethink some of my points. Thanks for that Modeller.
It got me looking at the feasibility of large scale direct air capture. Could we suck down CO2 from the 420ppm levels we are at now to say… 350ppm using direct air capture? Lets look at the figures…
So…what is the amount of CO2 that changes atmospheric CO2 by 1ppm? this is ~8 Gigatonnes (8x10⁹) of CO2.
Currently it seems to take between 1200 to 2000 kWhours of energy to remove 1 tonne of CO2 from the atmosphere.
That is a lot of energy. And 1 tonne of CO2 is about a return flight from Paris to New York. Or maybe 1/4 of emissions for driving your car, not SUV, around for a year.
So… to remove just 1ppm of CO2 using current technology would use:
8x10⁹ x 2x10⁶ Watthours of energy =1.6x10¹⁶ Watthours of energy
This is also ignoring the likely effect of CO2 that the oceans have taken up coming re-gassing back out of the oceans as atmospheric levels are reduced. I have no idea what that might end up being but could make it roughly twice as difficult.
Just taking the above figures, current global electricity production that could run direct air capture is 27 PetaWh (10¹⁵) or 2.7x10¹⁶Wh.
So, using current technology being used by people like Climeworks, it would take 60% of world electricity production to reduce CO2 levels by 1 ppm…assuming ocean CO2 out-gassing does not occur.
Or, to offset the 2022 2.5ppm increase in CO2 would we have to increase world electricity consumption by 50% and then use all of it for direct air capture :( …again assuming no ocean CO2 out-gassing occurs.
This is incredibly clear. Research shows re-vegetation using trees can play a somewhat limited role in reducing CO2 levels, but there is not enough land to plant enough trees to counteract our CO2 emissions.
Conclusions?
We can get close to zero emissions globally, but there will a bit of hard to do emissions reduction we could use excess energy in the middle of the day to run some direct air capture that could offset that. All of that combined with massive tree planting programs, CO2 levels could be slowly pulled down over many decades.
But it can’t happen quickly enough to avoid the West Antarctic and Greenland tipping points.
Also, every single kilogram of CO2 and methane going into the atmosphere right now matters. We need to rethink our flying and beef eating and SUV driving immediately. None of those things will solve this but can slow things down a little.
We cannot allow any new fossil fuel exploration or development. We need to be doing both emissions reduction and everything that also pulls CO2 down ie revegetation. So offsetting and carbon credits are complete green-washing. We are now at a stage where we cannot engage in activities that produce emissions and then somehow pretend we are doing something through an offset scheme. We need to both stop emissions and do those activities we might have counted as an offset.
And, unless we can some how develop some new technology that can take up CO2 at massive scale with much lower energy use, or turn around our emissions incredibly quickly in the next 10 years, we are locked in to as a species ~10m of sea level rise over coming centuries.
