Opinion piece by Commissioner Xue Lan 16 November 2023
The landmark Paris Agreement of 2015 set a goal of limiting global warming to well below 2 degrees Celsius and ideally closer to 1.5 degrees. But reducing emissions of greenhouse gasses is not on track, and warming is now at 1.2 degrees. All regions will experience the impacts of climate change, and low- and middle-income countries will bear them disproportionately.
Driven by such concerns, I took part in the work of the Climate Overshoot Commission to examine all the ways in which the risks of overshoot could be reduced and managed. We felt that no stone should be left unturned.
One novel approach we looked into is solar radiation modification (SRM). This is a highly contentious approach to reducing global temperatures by reflecting a small portion of incoming sunlight. The leading method would mimic the effect of large volcanic eruptions, which naturally cool the planet by spraying tiny particles into the upper atmosphere.
We approached this with caution and scepticism. After all, not only is the idea shocking, but solar radiation modification would come with environmental risks, both known and unknown.
What’s more, the political and governance challenges are daunting. For instance, because some SRM methods appear relatively inexpensive, individual countries might unilaterally proceed in the absence of a global consensus.
Yet, the potential and limitations of SRM should be evaluated in the context of rising climate risks. Scientific research on SRM is in its early stages and is far from supporting informed decision-making about its viability or non-viability, but present evidence suggests that it could complement other approaches to reducing climate harms.
First, and most importantly, emission reductions must remain the top priority and be accelerated. This is the only long-term solution to climate change.
Second, more research and more evidence are needed to produce a clearer picture of SRM’s potential efficacy and risks. China has the knowledge and resources to contribute in this regard. We believe it is better to know more than to know less, especially in a climate-stressed world.
Finally, the international community must proceed carefully. We call on states to adopt a moratorium on the deployment of SRM and large-scale outdoor experiments, and to regulate its research appropriately.
We strongly believe that SRM must not serve as an excuse to slow the urgent acceleration of emission cuts. At the same time, we reject going too far the other way by ignoring discussions on SRM or halting scientific research. It is time for some difficult, but unfortunately necessary and inescapable, conversations.
Xue Lan, Cheung Kong Chair Distinguished Professor and Dean of Schwarzman College in Tsinghua University, and member of the Climate Overshoot Commission