Headline: No Silver Bullet Against Climate Change

The 2018 COP24 climate conference in Katowice, Poland is over. Looking back at what has been achieved in the three years since the historical Paris Agreement reminds me a bit of the John Lennon lyrics: “So this is Christmas - and what have you done? Another year over, and a new one just begun.” While the conference was indeed successful in coming to an agreement over the rule book for how to account for countries upholding their commitments to limiting climate-relevant emissions under the Paris Agreement, there were no real breakthroughs.It is reassuring that the rule book was achieved, despite the considerable resistance from several countries, though it is exactly what was on the plan for this round of negotiations. Thus COP24 was another milestone in the steady progress being made towards implementing measures intended to help us achieve the chief goal of the Paris Agreement: keeping global warming well below 2°C, aiming to limit it to only 1.5°C.

The problem is that we will need more than steady progress: we still need some major breakthroughs, since at the pace that we’re going, we’ll fail to achieve the Paris Agreement goals…by far. Some look to technological developments, hoping for such breakthroughs. While these may someday become available, policymakers need to be cautious about what kinds of technologies they put their hopes on, or even count on being available in the near future. Prior to COP24 I published an editorial in the Süddeutsche Zeitung outlining my thoughts on this. Here, I’d like to expand on that article, also making the points available in English for a broader audience.

Let’s start with where we stand at present: Even if we make the optimistic assumption that all countries will follow their current commitments under the Paris Agreement framework (so-called “Nationally Determined Contributions”, or NDCs), then the global emissions of CO2 will still not decrease over the coming decade. Rather, they will stay about the same or even increase slightly. I call this “optimistic” since even the climate leader Germany will not meet its 2020 emissions goal (and thus will have to redouble its efforts to make its 2030 goal), and of course since some countries like the USA have announced their intention to pull out of the agreement altogether. Nevertheless, this “optimistic” scenario of everyone upholding their commitments – and the emissions still staying the same or even increasing slightly – is quite contrary to what one might expect if the world’s policymakers were really serious about meeting the Paris Agreement goals.

The implications of this are harrowing, especially for the 1.5°C goal. On average, climate models show that if we continue emitting CO2 and other climate forcers at the current global rate, then the amount of greenhouse gases in the atmosphere needed to push us past 1.5°C would already be reached by about 2030 (plus or minus a decade due to the usual scientific uncertainty). To emphasise how challenging the situation is: In order to have even a 50% probability of staying under 1.5°C, we would have to reduce CO2 emissions globally by about 5% per year, starting now – a tall order, given the average increase of nearly 2% per year over the last several decades, which has generally been coupled with economic growth. Such a drastic reduction would require an unprecedented worldwide transformative effort in all the major sectors of life, especially energy, mobility, agriculture and consumption. For 2°C, the message is basically the same, just delayed by about 10-20 years – and with much more drastic consequences for societies and ecosystems if we also miss that boat. This leaves us with an enormous puzzle for world leaders in environmental policy, science and civil society to solve.

Part of the problem is what we often think of as human nature: People and policy makers are reluctant to make major changes that take hard work, even for other very evident problems that are facing them. For example, how many people really manage to make lasting changes to their eating habits, which they can afford and know would be beneficial to avoid very direct, personal health consequences? And how long do cities like London, Los Angeles, Beijing and Delhi need to be choked with air pollution before people cry “enough!”, and effective measures are implemented to reduce pollutant emissions – even when relatively straightforward solutions are often at hand, but are blocked by the interests of large industries? Thus one can imagine what a challenge it is to garner motivation for action on something so abstract and seemingly far-removed as climate change. Nevertheless, evidence is mounting that we will have to make these transformations one way or another. The choice is not whether to deal with climate change or to ignore it, but whether we do so proactively, keeping the reigns collectively in our hands to decide how we transform these sectors and our behaviours to avoid more drastic environmental consequences, or reactively, always one step behind, having to adapt to the vast changes and impacts that accompany climate change, and perhaps also trying to develop expensive and controversial technologies to engineer our way out of the mess.

Indeed, in the face of such challenges, people often start to look for a “silver bullet” that can help come to the rescue. Such “Plan B” ideas have already been discussed for over fifty years. The various ideas can be distinguished into two main approaches: either actively removing CO2 from the atmosphere, for example by massive afforestation or chemically capturing CO2 from the air and storing it underground; or cooling the Earth by other means, such as injecting particles into the atmosphere to increase the amount of sunlight reflected back to space. These two hypothetical approaches are often referred to collectively as “climate geoengineering” (or similar names like “climate engineering” or “geoengineering”). Various proposed techniques are being investigated in theoretical, computer model, laboratory and field studies, and some small industries are developing around technologies for CO2 removal, although none of these techniques exist yet at anywhere near the huge scales that would be needed to significantly limit climate change. Researchers and activists involved in various aspects of investigating and debating the topic are well aware that all of the proposed techniques would only be a supplement for current efforts, perhaps helping to reduce the amount of climate change and its impacts, but that none of the techniques could actually replace the need for extensive mitigation and adaptation.

Based on a recent review of the scientific literature that I conducted with an international team of researchers, we conclude that some climate geoengineering techniques, especially for removing CO2, may become very important in the second half of this century. However, investigating, testing, and developing any of the techniques up to a climate-relevant scale would take considerable time. So would the development of adequate international agreements and governance mechanisms to limit conflicts that might arise around implementing any techniques. Thus, climate geoengineering cannot be relied on to contribute to significantly limiting global warming over the next several decades, the timescale noted earlier that is relevant for achieving the Paris Agreement temperature goals. This is challenging news for some policymakers and negotiators, who would like to keep the options open, especially for CO2 removal. Although no climate geoengineering options are prominently on the agenda of the climate negotiations, some have been implicit in the considerations for over a decade. For example, in the scenarios analysed in the 2013 assessment of the IPCC, over 90% of those that are likely to keep global warming below 2°C included substantial amounts of carbon dioxide removal, assumed to be accomplished by massive afforestation and by combining bioenergy with carbon capture and storage (“BECCS”). Such a strong reliance is also prominently present in one of the four illustrative scenarios in the recent IPCC special report on 1.5°C, although at least the report recognises that this strong reliance “…exceeds the BECCS potential…and afforestation potential…assessed based on recent literature”.

Although keeping global warming below 1.5°C (or even below 2°C) will be extremely difficult – or perhaps not possible at all, according to some climate models – and although we cannot count on a “silver bullet” like climate geoengineering to rescue us, it would not be sensible to simply resign in frustration. Every extra tenth of a degree warming that we can avoid will make a positive difference, especially for the most vulnerable, such as subsistence farmers, and those living in the tropics, the Arctic, small island states and coastal megacities. This is especially the case if the transformations in our social and industrial structures can be made proactively rather than reactively. Then we can capitalise on co-benefits, actions that are useful for limiting climate change, but that are also strongly motivated by improvements in other sectors. There are many such co-benefits, such as reducing the negative health impacts of air pollution (which is responsible for a considerable fraction of current global warming), increasing energy autonomy and long-term reliability, improving mobility through more efficient, seamlessly connected systems, and shifting agriculture practices supported by improved awareness of the health benefits of improved dietary habits. Although the overall transformations would have to occur on a national and global level in large societal systems in order to achieve the Paris Agreement goals, each individual and each small community can support this collective effort by watching for such opportunities for co-benefits on a local level, being strong in overcoming the resistance of current societal structures, and already taking brave and empowering steps towards making those changes in their daily lives.