The big idea: stopping climate change is not enough, it must be reversed | Books of science and nature

T.Last year witnessed an incessant drum beat of climate-induced disasters. Still, the climate history of the past decade has been a history of slow but steady progress. Global CO2 emissions have flattened out and countries accounting for 88% of global emissions have adopted or announced plans to reach net zero in the second half of the 21st century.

Another reason to hope is that clean energy has become cheaper much faster than expected. The cost of solar energy and batteries has fallen tenfold over the past 10 years and the cost of wind energy by two thirds. Solar is the cheapest form of new electricity to build today in much of the world, and electric vehicles now account for 13% of new vehicle sales globally.

But that doesn’t mean we can rest on our laurels. Far from it. We are still not far from where we need to be to reach our climate goals. In the most recent report by the Intergovernmental Panel on Climate Change (IPCC), to which I contributed, we found that if we want to limit warming to 1.5 ° C we can only emit 420 billion more tons of CO2, equal to about 10 years of current emissions. This means that, even with the progress we have made, the rise in global temperatures is very likely to exceed 1.5C by the early 1930s.

So where does that leave us? The short answer is: “It’s complicated”.

For starters, it’s important to point out that climate change happens incrementally rather than in big leaps. There is no evidence that 1.5C represents a boundary between manageable and catastrophic impacts. But the more we push the climate beyond where it has been in the last million years, the bigger and more unpredictable the risks become. Major climate changes in the Earth’s past and potential future tipping points such as the release of CO2 from thawing permafrost should make us reflect: we cannot easily predict what might happen. Every tenth of a degree is important if we want to minimize the damage we inflict on ourselves and leave it to future generations.

But similarly, just because we go above 1.5 ° C doesn’t mean there’s no going back. We know that if we can reduce emissions to zero, the world will actually stop warming. And climate models show that if we remove more CO2 from the atmosphere than we are emitting, the world will actually cool down. The removal of CO2 from the atmosphere and oceans was highlighted in the recent IPCC report as an “essential element” in achieving our climate goals. Virtually all climate models suggest that we need to remove 6 billion tonnes of CO2 per year by 2050 next to rapid reductions in emissions to bring temperatures back to 1.5 ° C by the end of the century.

A form of carbon dioxide removal that people are already familiar with comes in the form of trees and soil. Earth’s living systems already sequester about a quarter of the CO2 we emit today (with another quarter absorbed by the oceans). There is real potential to improve this “natural sink of carbon” by protecting forests, planting more and changing the way we manage farmland and pastures to get more carbon into the soil. This is a relatively low cost today, but it is also likely to prove temporary. Trees can be felled, burned, or die from beetle infestations, while the ground can dry out due to drought or heat and these risks will increase due to climate change. There are also limits to the land available for use. All in all, the models suggest that trees and soil could only provide half of the carbon dioxide removal we need.

There are other more reliable ways to remove carbon from the atmosphere in the long run. Such approaches are still in their infancy, but are rapidly being developed by hundreds of companies around the world. They include direct air capture, which draws CO2 directly from the atmosphere; taking agricultural waste or wood and storing carbon from it deep underground; spreading minerals such as basalt which absorb CO2 from the atmosphere to agricultural fields; remove CO2 directly from ocean water; make ocean water less acidic so that it absorbs more CO2; and sinking algae or other plants into the deep ocean where the carbon they have absorbed will remain for millennia to come.

These approaches are less likely to be reversed and are less limited by available land. But they tend to be a lot more expensive, at least at the moment. It follows that we should focus on making them cheaper, as we have done with renewables. That’s the goal of Frontier, a $ 925 million upfront market commitment that Stripe, where I’m head of climate research, launched alongside Alphabet, Shopify, Meta and McKinsey. The idea is simple: by guaranteeing money upfront, we’re sending a signal to entrepreneurs and researchers that if they build and scale those technologies early on, we’ll buy them. This approach was pioneered ten years ago to accelerate the development of pneumococcal vaccines in low-income countries and has saved around 700,000 lives.

We have a saying in the world of climate science: CO2 is forever. It will take nearly half a million years before a ton of CO2 emitted today by burning fossil fuels is completely removed from the atmosphere in a natural way. This means that when trying to neutralize or cancel fossil fuel emissions, for example with carbon offsets, those interventions should work over a similar time frame: a tonne of emissions from logging can be neutralized by putting in more carbon. in trees or soil, but CO2 from fossil fuels must be balanced by more permanent removal of carbon. This is why the respected Science Based Targets initiative only allows measures that permanently remove carbon from the atmosphere to neutralize a company’s remaining fossil fuel emissions in their net zero standard, and only in conjunction with profound reductions in emissions.

We shouldn’t underestimate the role of carbon removal. The vast majority of the time it is cheaper to reduce emissions than to remove CO2 from the atmosphere afterwards. Models limiting warming to 1.5 ° C show that we need to reduce global CO2 emissions by about 90%, using carbon removal for only about 10%. But 10% of the solution to a big problem like climate change is still something we cannot afford to ignore.

In 2021, the world spent a total of $ 755 billion on reducing emissions. We should probably aim to spend about 1% of that money on carbon removal technologies. But we can’t just sit back and assume that ways to remove billions of tons of CO2 per year will magically appear in the decades to come. By investing today, we can ensure that we are in a good position to make net zero a reality, prevent the world from continuing to warm up, and give us the tools to permanently reverse global warming in the future.

Further reading

End of Fossil Fuels: Why Net Zero Is Not Enough by Holly Jean Buck (Verso, £ 9.99)

Under a White Sky: Can we save the natural world in time? by Elizabeth Kolbert (Vintage, £ 9.99)

How to avoid a climate disaster: the solutions we have and the discoveries we need by Bill Gates (Allen Lane, £ 20)

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