Decarbonisation Is Not Enough
People in Canada are dying because it’s too hot. Roads in the UK are melting. It hit almost 32°C in Glasgow recently. And spare a thought for those humans who live in perennially warmer climes. In Quriyat, Oman, the lowest recorded temperature during one 24-hour period in June was 42.6°C.
So forgive me if I sound a little alarmist. Average global temperatures have already risen by more than 1°C since pre-industrial times. Atmospheric carbon dioxide (CO2) levels have risen by almost 50% — from 280 parts per million (ppm) to 410ppm, the highest they’ve been in 800,000 years. The rate at which Antarctic ice is melting has tripled in the last decade.
The Mercator Research Institute in Berlin has a countdown clock showing how long, at our current rate of emissions, until we’ve (literally) burned through our carbon budget. At the time of writing, it shows that there are just two months left until we’ve exceeded the amount of CO2 we can emit to have a middling chance of limiting global warming to 1.5°C. That’s the threshold that the governments of the world set as their aspiration in the 2015 Paris Agreement.
In short, unless the overwhelming majority of climate scientists turn out to be wildly wrong about how sensitive the climate is to increased levels of so-called “greenhouse gases” like CO2, we’re on track for a disastrous 3–6°C of warming by the end of the century.
So what should we do?
The obvious place to start is to stop emitting the stuff that warms the planet. The trouble is that this turns out to be fiendishly hard — probably impossible — to do over the kind of timescales we’re talking about to keep global warming below 2°C.
In the 30 years since climate scientist James Hansen testified to Congress about global warming — a pivotal moment in terms of bringing the issue into the political mainstream (and not just in the US) — the percentage of global energy demand met by fossil fuels has held steady at roughly 80%. Global energy demand has meanwhile gone up — and with it CO2 emissions — by more than 50%.
That doesn’t mean that we should stop trying to cut emissions — by switching to renewables (and nuclear), changing our diets (eating less meat), walking, cycling and using public transport more, and so on. Far from it. But it does mean we need other strategies to go alongside our so far fruitless quest for lower emissions.
This is the basic premise of Oliver Morton’s 2015 book The Planet Remade: How Geoengineering Could Change the World, which is by far the best exploration of those alternative strategies that I’ve come across.
Very crudely, the strategies he explores fall into two categories: first, removing carbon from the atmosphere, whether via biological or chemical processes; second, allowing less of the sun’s heat to reach the earth’s surface by creating some sort of stratospheric veil or increasing the propensity of clouds to shield us from the sun’s rays.
Let’s start with carbon removal since, as Morton acknowledges, it ‘is both ideologically more acceptable and politically more plausible than messing around with incoming sunshine. Moving carbon to safe stores feels more restorative than transformative, and sits well with common-sense notions of what to do when you have made a mess: clean it up.’
The most efficient method for removing carbon from the atmosphere that exists today is photosynthesis. Plants were in the business of CO2 capture and conversion long before humans came along and disrupted the natural carbon cycle and we certainly need their help now.
So yes, we can and should plant more trees and adapt farming practices to revive soil health, because healthy soil stores more carbon. And we should give photosynthesis a helping hand where we can: one of the great promises of genetic modification is that we might be able to make photosynthesis even more efficient, thereby reducing atmospheric CO2 and improving agricultural yields. We should temper our hubris on this front though, given that evolution has a 3.4 billion-year head start.
But there are limits to how much we can do with photosynthesis alone. While Morton supports adapting soil management, agronomy and forestry practices to increase carbon removal and storage, he ultimately concludes that ‘such actions do not store carbon on the scale needed to put a serious dent in the fossil-fuel-driven trajectory of atmospheric carbon dioxide, because the reservoirs into which they put the carbon are quite constrained. There is only so much woodland you can plant, only so much soil you can enrich, only so much farming you can do better. The biosphere is not that big.’
What about chemical processes for removing carbon from the atmosphere? These have garnered considerable attention recently as the first machines that capture CO2 directly from ambient air (as opposed to from an industrial chimney) have come online.
The semi-miraculous nature of direct air capture (DAC) is part of its appeal. Unlike traditional carbon capture and storage (CCS) technology, which has been around for decades but has not been widely deployed, DAC ‘suffers neither from being too mundane to thrill nor from being too simple to solve; it has Promethean world-changing promise, and finding a way to do it cheaply looks really hard.’
Progress is being made on the cost front. Recent evidence from the Canadian company Carbon Engineering suggests that they’ve found a way to do DAC at a cost of less than $100 a tonne. If true (their claim was published in a reputable scientific journal and subject to academic review, so we should take it seriously), this is a major improvement on previous costings of DAC, which have consistently been in the $300–600 a tonne range. But $100 a tonne is still not exactly cheap: at that level, the contexts in which DAC will prove commercially viable will remain fairly limited. ‘Measure them in tens of thousands of tonnes a year, not in billions,’ suggests Morton.
And much as we might wish to believe that the cost-reduction curve for DAC will follow an exponential trajectory, the laws of thermodynamics suggest otherwise. Extracting nitrogen directly from the atmosphere — as humans do all over the world to make fertiliser — is relatively easy because four out of five molecules in the air we breathe is nitrogen. Even after centuries of industrial CO2 emissions, it makes up just 0.04% of the atmosphere — that’s one molecule in every 2,500. A process where you have to filter out 2,499 molecules for every one you capture is inherently inefficient.
In this respect at least, capturing CO2 directly from the chimneys of fossil fuel power stations (CCS) should be more promising, since the concentration of CO2 is significantly higher and the process therefore more efficient. But CCS has so far conspicuously failed to take off, partly due to political resistance — the technology has largely been developed by fossil fuel companies as a way of prolonging their own life expectancy, with much of the captured CO2 being used for ‘enhanced oil recovery’; unsurprisingly, it hasn’t been wildly popular with environmentalists — and partly due to economics.
As Morton writes, ‘if companies thought they could make money from storing carbon underground they would probably find a way to do so in the face of opposition, just as in many territories they have found ways to frack.’ CCS at scale, he concludes, will not thrive without a stable price on carbon of at least $50 a tonne. And that price would need to be paid ‘as readily for the billionth tonne as for the first.’
There is one final issue that afflicts both biological and chemical carbon removal options: the counterbalancing effect of the ocean. ‘If you push carbon dioxide into the atmosphere the seas suck some of it up; if you pump carbon dioxide out of the atmosphere the seas give some up, reducing the effectiveness of your pumping. This means that to get a net reduction of a billion tonnes of carbon in the atmosphere, you need to pull out well over a billion tonnes.’
So what of the other forms of geoengineering Morton considers — those that involve altering not the carbon cycle but the way the sun’s radiation effects surface temperatures? In essence, the ideas presented all boil down to one thing: reflecting back more of the sun’s rays into space.
One option is to create a veil of aerosols in the stratosphere, artificially replicating, on a longer-term basis, the short-term cooling effect that has historically followed major volcanic eruptions. This is the result of the vast quantities of sulphur dioxide that volcanoes spew into the stratosphere. Morton (and others who favour this form of solar geoengineering) envisage sulphur dioxide being delivered to the stratosphere by fleets of very high-flying aircraft — successors, in a way, to the spy planes of the early Cold War.
A little nearer the ground, tampering with the brightness of clouds could also offer a cooling effect. Unlike the stratospheric veil option, which is by necessity a global intervention, cloud brightening could be done at a more local level, to protect precious coral reefs perhaps, or to lower sea-surface temperatures in order to forestall hurricanes.
There’s a potential danger in such a patchwork approach: the global climate is a fiercely complex interconnected system and small changes in one place can have big knock-on impacts half a world away. But, so long as cloud brightening remained truly local and informed by suitably rigorous modelling to assess possible side-effects, Morton concludes that it may well be a risk worth taking in many instances.
In discussions about climate solutions, geoengineering of this sort, if considered at all, is generally seen as a last resort. It’s sidelined both for its unnaturalness — most of us instinctively recoil from the thought of humans wielding the power to (partially) block out the sun — and because of the fear that it creates a form of moral hazard — if we know that we can, ultimately, save ourselves with a giant space parasol, why bother with the hard work of cutting emissions?
Morton addresses both these objections in some detail (read the book if you want to know how) and then makes an intriguing counter-suggestion: rather than a back-up option to be rushed out when we’re facing climate catastrophe, solar geoengineering, he argues, should be used now to give us a few decades’ breathing space in which to cut our emissions to zero and re-balance the carbon cycle.
What’s more, in a richly imagined set of scenarios in the book’s final chapter, Morton makes such a possibility seem remarkably plausible. He envisages, in the near future, a small group of nations taking it upon themselves to create and maintain a stratospheric veil. All sorts of things could go wrong with such a scheme, but the key to its plausibility lies in the relative immediacy of cause and effect when it comes to solar geoengineering as compared with changing the quantity of carbon in the atmosphere.
What makes climate change such a difficult problem to solve, ironically, is its slowness. Whether global emissions go up or down today will have a major bearing on what happens several decades from now, but neither the costs of inaction, nor the benefits of action, are felt in the present. Add to this the fact that what matters is the sum of all human activity — cutting emissions in one country whilst they continue to soar in another country is of limited use — and it’s no wonder climate change (when seen purely as a carbon issue) feels so intractable.
With solar geoengineering, on the other hand, ‘you don’t have to coordinate the actions of many different players in advance. You don’t have to wait for another generation to see the effects. There are clear responsibilities and prompt effects, and that would seem to make the problem inherently more tractable.’
This does not mean that solar geoengineering is a silver bullet. Morton explicitly rejects the notion that geoengineering is a solution for climate change, adding that ‘I think that it is a mistake to treat climate change as a problem to be solved. Something as complex as the relationship of industrial civilisation to the earthsystem that it shapes and is shaped by isn’t the sort of thing that is simply solved, once and for all, and it’s a snare to think that it is.’
There are no either/ors left, then, when it comes to addressing global warming. Cutting emissions, removing carbon from the atmosphere and ‘messing around with incoming sunshine’ are all necessary paths to pursue. Ideas that have long been the preserve of science-fiction writers and a small clique of scientists are now too important to leave to those groups alone.
It’s all-hands-on-deck time here on Spaceship Earth.
