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The Climate Conversation No One Wants

It’s time to talk about managing the world’s likely overshoot beyond 1.5 degrees Celsius.

By , the executive director of the Carnegie Climate Governance Initiative and the former U.N. assistant secretary-general on climate change.
The sun shines in a hazy sky over mechanical equipment at Tanjung Priok sea port.
The sun shines in a hazy sky over mechanical equipment at Tanjung Priok sea port.
The sun rises over the Tanjung Priok sea port in Jakarta, Indonesia, on June 21, 2007. Ahmad Zamroni/AFP via Getty Images

The U.N. climate change conference in Glasgow, Scotland, brought a series of positive steps for implementing the Paris Agreement. It also reinvigorated U.S.-China cooperation and offered opportunities for voluntary initiatives on methane and forests. There was a whirlwind of “net-zero” pledges made by governments and the private sector—but without any common understanding of what this actually means and how to get there. Leaders were keen to claim the Glasgow climate pact kept the goal of limiting global warming to 1.5 degrees Celsius above preindustrial levels alive, thus avoiding an overshoot of the Paris temperature goal.

Taken together, however, the Glasgow outcomes were likely too little, too late by the only criteria for success that ultimately matters: the atmosphere. All the pledges bandied about in Glasgow obscured a key fact: We have likely set in motion a less stable, hotter, and more extreme climate in our lifetime—a climate that will recast much of civilization as we know it for future generations.

Even if all Glasgow pledges are fulfilled, we are still facing a temperature overshoot of approximately 2 degrees Celsius. In the more likely scenario of not all pledges being fulfilled, warming will be more: perhaps 3 degrees Celsius. This would be catastrophic in nearly every sense for large parts of humanity, especially the poorest and most vulnerable who are suffering first and worst from escalating climate impacts. Extreme weather events are becoming much more frequent, and no one will be totally immune, as we saw with Europe’s 2021 floods and Colorado’s recent fires.

The U.N. climate change conference in Glasgow, Scotland, brought a series of positive steps for implementing the Paris Agreement. It also reinvigorated U.S.-China cooperation and offered opportunities for voluntary initiatives on methane and forests. There was a whirlwind of “net-zero” pledges made by governments and the private sector—but without any common understanding of what this actually means and how to get there. Leaders were keen to claim the Glasgow climate pact kept the goal of limiting global warming to 1.5 degrees Celsius above preindustrial levels alive, thus avoiding an overshoot of the Paris temperature goal.

Taken together, however, the Glasgow outcomes were likely too little, too late by the only criteria for success that ultimately matters: the atmosphere. All the pledges bandied about in Glasgow obscured a key fact: We have likely set in motion a less stable, hotter, and more extreme climate in our lifetime—a climate that will recast much of civilization as we know it for future generations.

Even if all Glasgow pledges are fulfilled, we are still facing a temperature overshoot of approximately 2 degrees Celsius. In the more likely scenario of not all pledges being fulfilled, warming will be more: perhaps 3 degrees Celsius. This would be catastrophic in nearly every sense for large parts of humanity, especially the poorest and most vulnerable who are suffering first and worst from escalating climate impacts. Extreme weather events are becoming much more frequent, and no one will be totally immune, as we saw with Europe’s 2021 floods and Colorado’s recent fires.

Remember this word: overshoot. It will gain increasing importance as the herculean difficulty of reducing emissions to net zero and removing vast stores of carbon from the atmosphere become clearer. On top of this, there is a still greater challenge: moving to net-negative emissions thereafter, which the Intergovernmental Panel on Climate Change (IPCC) says will also be needed.

So how do we avoid temperature overshoot? The most urgent and important task is to slash emissions, including in the hard-to-abate sectors (such as air transport, agriculture, and industry), which will require substantial lifestyle changes. Carbon dioxide remains in the atmosphere for centuries, trapping heat like a blanket over our planet. Technologies to remove carbon, however, are not yet at scale—and won’t be for years to come. Nor have they been vetted by society. In other words, we are pinning our hopes for avoiding climate chaos on a level of global political will not yet evident and on carbon removal technologies not yet available.

Given the gravity of the crisis, some are exploring the use of emerging techniques—solar radiation modification, commonly called solar geoengineering—that would deliberately alter the climate. The most widely discussed method would create a sun shield, composed of aerosols injected into the stratosphere, that would reflect sunlight back into space and thus quickly cool the planet. It would affect every country in the world, though not necessarily equally, thus creating global winners and losers.

Worryingly, some might erroneously see solar radiation modification as an easy way out, especially since cooling would occur very quickly—within a year—and the direct cost of a technique such as aerosol injection would be relatively cheap (between $1­ billion to $10 billion annually). This is within the means of many countries, companies, and even wealthy individuals. Others fear it could divert the world’s attention from doing what it must do no matter what: slash emissions and remove massive amounts of carbon from the sky.

Solar radiation modification can never be a substitute for mitigation, as it does not directly address climate change’s source. At best, it might be a supplement that could provide immediate cooling in a temperature overshoot scenario. Some say it might buy the world more time to finish decarbonizing economies and remove excess carbon from the atmosphere, thus possibly helping to safeguard some sustainable development achievements and avoid some of overshoot’s irreversible damages as well as planetary climate tipping points.

However, as with overshoot scenarios, this technique also poses serious potential risks, both known and unknown, for the environment, biodiversity, and geopolitical security as well as significant ethical concerns.

Take international security, for example. Imagine if Country A began deploying solar radiation modification seeking temperature relief for its people, but neighboring Country B experienced a terrible drought at the same time that may—or may not—have been provoked by using this technique. Scientific attribution would be tricky, and the potential for misperceptions that trigger conflict is obvious.

Another challenge is once this technique starts, it cannot be stopped suddenly, either purposefully or by accident, as the temperature would rapidly rise to its previous level—a sort of climate whiplash scientists agree would devastate biodiversity.

One of the greatest risks is a current lack of governance. There are no comprehensive international frameworks to provide global guardrails and guidance on how this technology may (or may not) be researched and potentially deployed. Any consideration of potential deployment would depend on effective governance systems spanning many decades, potentially even centuries, premised on global cooperation and goodwill the likes of which the world has never seen before.

Let’s start with the basic questions. Who decides if this technique should be further researched and/or used? Based on what authority and using what evidence? Who would control the global thermostat? Would all people impacted by its use, especially the most vulnerable, have a say? How might society assess the risks of deploying it against the risks of not doing so? Should we prepare the ground for such a decision now or leave it to our children and grandchildren to decide when the climate crisis will have deepened still further?

There are also profound ethical issues involved: Does humanity have the right to intentionally alter the climate system? Does this not imply a level of human hubris that far exceeds our capacity to understand something as complicated as the global climate? And does it fall into the same type of techno-fix-driven thinking that helped create the climate crisis in the first place?

One might also ask the opposite questions: Do we have the right to withhold research and possible use of solar radiation modification given it would likely cool the planet quickly and thus benefit hundreds of millions of people who otherwise would be suffering from extreme heat and other related climate impacts?

Knowledge about these issues is frighteningly scant, yet decisions policymakers may one day face will have profound consequences. We cannot afford to put our heads in the sand. To wait is to increase the risk that, as temperatures continue to climb, someone or some group of actors, somewhere, some day will move without effective international governance in place. Solar radiation modification is being researched in multiple countries, and interest is growing, including from some of the world’s most climate-vulnerable nations.

The world simply does not know enough at this stage, which is why it needs governance, including broad, transparent, societal dialogues about the potential pros, cons, and implications of this climate-altering technique.

We also need similar clear-eyed discussions about the risks and implications of living in a world that overshoots 1.5 degrees Celsius. We must weigh the risks of solar radiation modification against the risks of an overheated world that will have devastating impacts for human health, socioeconomic development, and international security for all countries—but especially the poorest ones.

In which scenario will the world be better or worse off—and better for whom? In which will climate justice best be served? This is the climate policy conversation the world needs to have now, not years down the road.

Given all countries would be affected, the United Nations—an imperfect body but one that reflects our imperfect world—is well placed to be the focus of governance efforts. The U.N. General Assembly can debate these issues from a cross-sectoral perspective and provide high-level guidance on potential directions and their implications. Other U.N. bodies—such as the U.N. Environment Assembly, the IPCC, or the U.N. Framework Convention on Climate Change—as well as non-U.N. bodies can address different components of the risks, benefits, and governance challenges that come with this new, emerging technique.

COVID-19 has showed us that anticipating global risks, collaborating across borders, and putting in place effective and agreed on global guidelines all of us follow could have saved millions of lives and reduced overall suffering. We have failed this test thus far. As 2022 begins and we face a third year of the pandemic, let us not fail this test with the climate crisis.

The world is getting warmer, and we need to start talking about how to manage overshooting beyond 1.5 degrees Celsius, including considering the risks presented by any potential use of solar radiation modification. These discussions and the development of needed governance frameworks will not be easy, but they are necessary. The sooner we have this discussion, the better for us all.

Janos Pasztor is the executive director of the Carnegie Climate Governance Initiative and the former U.N. assistant secretary-general on climate change.

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