The case of geoengineering | The Economist

TEVALUATION of climate change science published by the IPCC in August examined various scenarios of future emissions. In each, the best estimate of the temperature difference between the mid-19th and mid-21st centuries was greater than 1.5 ° C. Only two scenarios, with net emissions close to zero in the middle of the century and net negative emissions thereafter, had the best estimates below 2 ° C for the last two decades of the century.

What the report did not say was how the world would pay for the negative net decades needed to provide a climate that is both stable and within temperature limits of Paris. In a net zero economy, it is possible to imagine “polluter pays” schemes in which emitters pay for negative emissions that cancel their activity. They could eventually evolve from emission trading systems like the EU‘s. But once you need to remove more CO2 that what is put in an insufficient number of polluters makes things more delicate.

Some companies, including Microsoft and Ikea, plan to go net negative at their own expense. They aim to remove from the atmosphere an amount of carbon equivalent to all the emissions for which they have been responsible during their business life. But it’s unlikely that all the big emitters will volunteer to behave so admirably.

An imaginative group of academics writing in the journal Nature recently described a polluter pays system that could force companies to become at least somewhat carbon negative. Long before net zero is reached, emissions would begin to attract a “carbon removal obligation” requiring subsequent removal. To encourage companies to act quickly, the obligations would increase over time: leave one tonne in the air long enough and two tonnes would have to be taken out. It’s an ingenious idea. But that would do nothing to remove the shows produced before the start of the program.

It’s hard to imagine negative emissions on a scale large enough to offset the overspending of the carbon budget paid by anyone except governments. Any agreement on how to do this would surely reflect a version of ‘common but differentiated responsibilities’: countries disproportionately responsible for using the carbon budget in the first place would be asked to shoulder most of the burden of managing the overshoot. . In a world where rich countries had already invested heavily to help the poorest reduce their emissions, this additional expense could be borne voluntarily. But it is also possible that this is not the case.

What is more, in a world where some, arguably richer, countries have enough negative emissions capacity to reach net zero and beyond, other countries – either poorer or simply more insane – might abandon further emission reductions, betting that countries with negative emissions capacity would rather increase their use of that capacity rather than see CO2 level continues to rise.

They could win this bet; they might not. It is too easy to imagine a world where most people in poor countries continue to believe that climate change is not their fault and that someone else should fix the problem, while people in countries wealthier people don’t want to shoulder the full burden of doing so. A dead end develops in which overshoot is never sucked in and temperatures end up stabilizing at a level considerably above 2 ° C above pre-industrial levels – if they stabilize at all.

The alternative to this chicken game would be to meet Paris temperature limits in other ways. Solar geoengineering is an approach to climate that is not aimed at making the Earth cooler, like removing carbon dioxide, but at preventing it from heating up that much in the first place. The way to do this, which has been studied in detail, although almost entirely in models, is to create a thin layer of reflective particles in the stratosphere that reflects sunlight back into space before it warms the surface. . Studies suggest that, for better or worse, such a program could be implemented by a relatively small fleet of specially designed aircraft.

These ideas have, for understandable reasons, been marginalized for a long time in political circles. They reek of pride and the potential for unintended consequences. And if, by providing another means of limiting temperature rises, they reduce the perceived urgency to reduce emissions, they could weaken or even delay the commitment to reduce emissions.

It would be disastrous. Although it has the opposite effect on temperature, the cooling offered by solar geoengineering is not, in physical terms, an exact counter to the warming created by greenhouse gases. A difference is observed in the global hydrological cycle; solar geoengineering tends to suppress precipitation. The more the world relied on it, the more harmful this mismatch and others would become. This, along with the fact that it does nothing against ocean acidification, is a big part of the reason researchers who seriously study solar geoengineering never advocate using it instead of mitigating it. . Those who are not completely discouraged by this see it as a possible complement to mitigation, not an alternative.

In this, it sounds a lot like negative emissions – one of the reasons they are sometimes referred to as “carbon geoengineering”. How a solar geoengineering capability might reduce the incentive to continue reducing emissions is similar to how existing negative emissions capability might work. And in either case, this reduced ambition could well occur even if the proposed geoengineering did not.

A crucial difference between the two, however, is the cost of their incentive. It seems likely that putting a veil on the atmosphere would be relatively inexpensive (in the order of tens of billions of dollars per year, maybe even less), although the externalities not included in the cost can be high. Another difference is that negative emissions would affect the climate in more or less the same way that undertook them; the global level of carbon dioxide is what it is. However, different kinds of solar geoengineering would have very different regional effects.

Design to live

If the world as a whole were able to design a solar geoengineering program, studies suggest it could come up with one that would bring climate benefits to almost everyone and serious problems to almost no one. A plausible way to use such an optimal scheme might be to compensate for the temperature rise caused by the carbon budget overrun. This would provide some sort of breathing space to allow excess CO2 be fired more slowly and more cheaply than would be necessary if its warming effects were to be felt. A relatively smooth acceleration of chemical weathering, rather than a huge investment in CAD or other regimes, may be sufficient. As these measures slowly carried the overshoot, solar geoengineering could be curtailed. When the CO2 the level was low enough to be completely eliminated, leaving behind a stable climate.

But the world as a whole might not choose the wisest path. A small group of countries, if not a single large one, could unilaterally undertake a solar geoengineering project. Such a club would be likely to optimize its own interests rather than those of the world. He might, for example, choose to cool some places to a degree that, due to the effects of geoengineering on the water cycle, risks drying out others. This could lead to resentment, resentment or retaliation.

Likewise, no given group of solar geoengineers would be sure to do things their own way. The late Marty Weitzman, a pioneering climate change economist, pointed out that while emission reductions (and by implication negative emissions), because of their cost, have a stowaway problem, solar geoengineering, because that it looks cheap, has a “driver problem.” When free rider problems lead to under-supply (countries are unwilling to commit to reducing emissions while others are not , because 26 years of COPits clearly stated) Free pilot problems can lead to overprovision. Solar geoengineering seems cheap enough that countries that want more can provide it unilaterally, no matter what others think.

This implies that, all other things being equal, the level of solar geoengineering would be a trade-off between how much more enthusiastic countries wanted and how much less enthusiastic countries would incur before taking decisive action, most likely by force. weapons. Another chicken game.

The challenges of negative emissions and solar geoengineering are very different, and the second seems much more unknown and threatening than the first. But in both cases, the problem is fundamentally similar and closely linked to the contradiction between the global temperature targets and the national emission reduction commitments at the heart of the Paris Agreement. The world has needs that we can agree on; but the decisions necessary to meet these needs are made by countries that differ in their interests, capacities, and the degree of persuasion they can exercise or resist. Responsibilities can be shared; the differentiation is endless.

Glasgow will show to what extent national governments are able to make progress in terms of increased ambition of their NDCs, achieving the long-promised money transfers from north to south, and workable rules for parts of the Paris agreement that remain unclear. Progress is unlikely to be dramatic, which reinforces the fact that managing global issues like climate only through national lenses is impractical. But to offer an alternative in which individual countries will allow the interests of others to be placed above their own is implausible. And if the world is to stabilize the climate to an acceptable level, something will have to give way.

The climate crisis was triggered as part of the creation of a new global economy. To achieve this successfully may require a new global policy. Failure to do so would be catastrophic both politically and economically.

Full content of this special report
The COP 26 summit agenda: Stabilizing the climate
What the 2015 Paris Agreement meant: the state of play
How Asia is Crucial in Addressing Climate Change: Emissions from the Asian Century
Climate economics: Economy and energy
Why the world needs negative emissions: Negative emissions
The case of geoengineering: veils and ignorance *

This article appeared in the Dossier section of the paper edition under the title “Governing the atmosphere”

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