rethink sustainability

Trigger warning: five ways to buy time for net zero and prepare for net negative

According to a now famous analogy1, we face a ticking clock that is counting down to disaster.

We all know that the severity of the climate change we’re likely to see in the future is relative to the amount of CO2 we’re pumping into the atmosphere. This process is analogous to a bath with a dripping tap—although the bath will take a long time to fill, it will inevitably do so unless you turn the tap off completely. Leave the tap dripping—or, even worse, open it further—and the bath will eventually overflow. In turn, the moment of overflow is analogous to an environmental trigger: the point at which we’ve put so much CO2 into the atmosphere that climate change becomes irreversible, potentially destroying our environment in the process. This model is evidently no longer sustainable.

If we are to have any hope of limiting and reversing the increase to global temperatures, there’s no question that we must make net zero one of this century’s top priorities


Turning off our carbon tap is what net zero is all about. If we are to have any hope of limiting and, eventually, reversing the increase to global temperatures, there’s no question that we must make net zero one of this century’s top priorities.

But what if there’s more to net zero than simply turning off the tap?


The other factor

While the rate at which the tap is adding water to a bath is, of course, highly relevant to the rate at which the water level is rising, it isn’t the whole story. After all, most baths are also equipped with a drain—the faster the drainage, the longer it’ll take to fill.

In the same way, even as we continue to pump CO2 into the atmosphere, Earth’s carbon sinks, such as our forests, soils and oceans, act as a natural CO2 drain. The importance of these carbon sinks cannot be overstated. Without them, the CO2 we’ve already emitted might have been enough to cause irreversible, cataclysmic climate change.

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The good news is that the rate of CO2 drainage isn’t fixed. There are things we can do to both increase the capacity of existing, natural carbon sinks; and to create new, artificial ways of removing CO2 from the atmosphere. And, even as we work towards turning off our carbon tap, it’s crucial that we also focus on preserving, expanding and creating carbon sinks, for two reasons.

First, achieving net zero is a long process, and in some areas—especially in hard-to-abate industries—many questions remain about how we will get there. So, alongside ingenuity and sheer will, the other thing we need to achieve net zero is time. To invest in carbon sinks, then, is to buy more time to turn off our carbon tap before we reach the trigger point.

Second, while you must turn off the tap to stop the water level from rising, the only way to reduce the water level is to pull the plug and let it drain. Even after we’ve achieved net-zero emissions, then, we’ll need to pull the plug on the CO2 that’s already in the atmosphere if we want to begin reversing the effects of climate change. The more we invest in our carbon sinks now, the better positioned we’ll be to achieve the net-negative emissions we need to decarbonise the atmosphere.

The more we invest in our carbon sinks now, the better positioned we’ll be to achieve the net-negative emissions we need to decarbonise the atmosphere

 

Five carbon sinks that could help us achieve net zero and begin reversing climate change


1. Protect and regenerate our forests

Photosynthesis removes significant amounts of CO2 from the atmosphere, which makes our forests one of our most important natural carbon sinks. As such, reducing deforestation and increasing afforestation and reforestation will help expand the capacity of this particular CO2 drainage system.

For investors, this means favouring companies that are either moving away from relying on deforestation to make their products or, where this isn’t possible, that are committed to restoring—and, ideally, adding to—the trees they remove.

There are also indirect ways to support our forests. For instance, investing in innovation that enables more food to be produced on less land would not only make agriculture more efficient; it would also free up fields to be converted back into forests without affecting productivity.

Photosynthesis removes significant amounts of CO2 from the atmosphere, which makes our forests one of our most important natural carbon sinks

2. Accelerate the ocean’s natural carbon cycles

Although we tend to see our oceans as one big carbon sink, they actually remove CO2 from the atmosphere in many different ways—each of which could offer a way to ramp up the drainage capacity of the oceans.

Like forests, oceanic flora such as seaweed remove a great deal of carbon from the atmosphere via photosynthesis, the cultivation of which would enable even more CO2 drainage. Meanwhile, minerals could be added to the ocean to sequester more carbon in dissolved bicarbonate. We could even pump nutrient-rich water from the depths of the oceans to the surface, triggering algae blooms that would sequester carbon from the atmosphere.

While there are many options to explore, we need much more research on their potential effects on the environment and society before we can risk pursuing any of them at scale. And as these methods seem unlikely to make much contact with the free market, we also need governments to be more eager to fund such carbon sinks as a public good for these methods to be commercially viable.


3. Build carbon in agricultural soils

For thousands of years, the carbon that soils naturally sequester has made a direct contribution to farming—the more carbon in the soil, the better the crop yield tends to be. But as the human population has grown, farmers have been forced to use their fields more intensively to keep up with demand. As a result, a great deal of CO2 has been released from agricultural soils, making it more difficult to maintain crop yields in the process.

Finding ways to help agricultural soils store more carbon…would have the triple benefit of removing more carbon dioxide from the atmosphere, ramping up food production and helping farmers


Finding ways to help agricultural soils store more carbon, then, would have the triple benefit of removing more CO2 from the atmosphere, ramping up food production and helping farmers—many of whom are struggling—turn a profit. And there are plenty of options—from planting not-for-harvest cover crops in off-seasons for year-round CO2 storage, to using newly developed crops with deeper roots that sequester more carbon than their shallower-rooted counterparts.

There are two big challenges here. The first is in figuring out which of the methods available are most effective over time—a matter that is not only the subject of ongoing debate, but which is also complicated by the fact that local conditions also play a significant role. Next, better soil alone is unlikely to be enough of an incentive to create change at the scale we need for agricultural soil CO2 sequestration to make a significant difference. So, aside from financial backing from governments, responsible investors also have a role to play in creating the incentives we need to encourage the industry to prioritise soil carbonisation by favouring agricultural businesses that are committed to changing their practices for the better.


4. Combine bioenergy with carbon capture and storage

Photosynthesis doesn’t just sequester carbon in our forests—every plant on Earth is, in essence, its own little carbon sink. And since much of this biomass can be used to generate energy in place of fossil fuels, cultivating it for that purpose could amount to a net reduction of the amount of CO2 in the atmosphere—provided that it’s combined with carbon capture and storage (CCUS). Here, various technologies are used to trap the CO2 emitted by bioenergy production before it enters the atmosphere as emissions. Then, it can either be sequestered using mineral or geological storage methods or used to make products—ideally, those likely to hang around for a long time, such as concrete.

Photosynthesis doesn’t just sequester carbon in our forests - every plant on Earth is, in essence, its own little carbon sink


One snag here is the amount of land we’d need to grow suitable crops, which would risk reducing food production capacity or damaging fragile ecosystems if not done carefully. In addition, carbon capture technologies remain expensive and unproven at scale, and so we need more investment in developing these young technologies.


5. Deploy direct air capture technologies

The most straightforward way to remove CO2 from the atmosphere—in principle, at least—would be to simply grab it by deploying chemical scrubbing technologies designed for that purpose.

Of course, in practice, direct air capture is a complicated project. Like any new technology, it’s still prohibitively expensive, not to mention the fact that it requires enormous amounts of energy—all of which would need to produce minimal or, ideally, zero carbon emissions if direct air capture isn’t to cancel itself out. And since there are no obvious market applications for such technologies, governments must be willing to fund their deployment as a public good at scale for direct air capture to be commercially viable—something which they have yet to muster sufficient enthusiasm for.

Buying more time to achieve net zero before we reach the crucial CO2 trigger point and positioning ourselves for the subsequent transition to net-negative emissions by investing in carbon sinks is both viable and vital

And yet, with growing recognition around the urgent need to achieve net zero, there is cause to be optimistic about direct air capture technologies—albeit optimism that, as with all of the options for CO2 drainage we’ve looked at, must be tempered with public support and far-sighted investment strategies.

Buying more time to achieve net zero before we reach the crucial CO2 trigger point and positioning ourselves for the subsequent transition to net-negative emissions by investing in carbon sinks is both viable and vital. So, we must figure out how to move forward in earnest. Because the tap is dripping—and the clock is ticking.

1 Armstrong, A. K., Krasny, M. E. and Schuldt, J. P. (2018) ‘Using Metaphor and Analogy in Climate Change Communication’, in Communicating Climate Change, A Guide for Educators, Cornell University Press, pp. 70–74.

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