Preparing for Climate Overshoot
Humanity’s continuing failure to reduce greenhouse-gas emissions has substantially increased the likelihood of global warming exceeding 1.5°C within the coming decades. That means we must start exploring a wider set up options for mitigating the worst consequences and managing life in a warmer world.
PARIS – The latest report from the Intergovernmental Panel on Climate Change revealed what many had feared but were reluctant to admit: the continued failure to reduce greenhouse-gas emissions means that global warming will likely exceed 1.5° Celsius, relative to pre-industrial levels. UN Secretary-General António Guterres has warned that this key goal of the 2015 Paris climate agreement is now on “life support.” Even if emissions “peak before 2025 at the latest,” notes the IPCC, and are “reduced by 43% by 2030” (including a one-third reduction in methane), “it is almost inevitable that we will temporarily exceed this temperature threshold but could return to below it by the end of the century.”
If avoiding a breach of 1.5°C is still technically possible, we should of course not give up. But the window of opportunity is closing faster than we thought, and deepening geopolitical divisions – intensified by the pandemic, Russia’s aggression against Ukraine, and looming food, energy, and debt crises – do not augur well for the kind of cooperation that we need.
By surpassing 1.5°C, but then taking measures to bring temperatures back below that threshold by the end of the century, we will be in what the IPCC calls an “overshoot” scenario. Although climate models have long accounted for this possibility, not much is known about how to reduce the risks – both environmental and political – that it would create.
Average global temperatures have already risen 1.1°C above pre-industrial levels, with significant environmental effects. Every additional tenth of a degree contributes further to the severity and frequency of extreme weather events and increases the risks to health, food, water, livelihoods, and biodiversity. By the time we reach 2°C, many human and natural systems will be under extreme stress; some ecosystems will struggle to survive, and others already will be gone.
Worse, overshoot increases the risk of what the IPCC describes as “cascading and irreversible climate impacts.” And the political consequences would be no less significant. For many, 1.5°C has become a line in the sand – a signifier of humanity’s ability and will to reduce climate risks. While breaching it could lead to a more forceful response to climate change, it also could invite despondency and fatalism. That is why we must start planning for it now.
To that end, I will be chairing a new Global Commission on Governing Risks from Climate Overshoot. Consisting of 16 eminent leaders with diverse backgrounds, we will consider how best to manage the physical and political risks of a world beyond 1.5°C. Most of the commission is from the Global South, including several former heads of government, minsters, and senior officials. We will present an integrated strategy to tackle the possibility of climate overshoot ahead of the 2023 UN Climate Change Conference.
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As an independent commission, we will conduct this important work without the political and organizational constraints that so often hamper such discussions. We are ready to consider all the options, including ideas that are sometimes considered too controversial to broach in other fora.
For example, while reducing greenhouse-gas emissions is and should remain our primary goal, we must recognize that this is no longer enough. Additional approaches are now in order. For example, we will explore the potential of removing carbon dioxide from the atmosphere on a large scale. This is unavoidable if we want to achieve net-zero emissions, let alone the net-negative emissions that are needed to start restoring our planet. But while there are many ways – both nature-based and technological – to remove CO2, none is ready at scale, and many elements of this strategy remain contested.
We also will explore avenues for improving and expanding adaptation efforts on the scale needed to address the growing effects of climate change, though the limits of what is feasible here remain unclear. Finally, we will examine the research on “sunlight reflection methods,” an intervention designed to reflect a small portion of incoming solar radiation back into space. This option appears to be viable, but it would pose global risks, implying significant governance challenges.
Our aim is to bring all these options together into one document for the first time, to weigh the risks of action against the risks posed by a rapidly warming world, and to recommend an integrated strategy based on independent scientific advice and stakeholder consultations. Our overshoot strategy will need to be effective, robust, and ethical, grounded in the best available evidence, and consistent with justice, equity, and respect for international law. As long as these principles apply, we will keep an open mind. At this 11th hour, we cannot afford to take any options off the table – at least not until we have investigated them fully.
It is tragic that we must confront the consequences of insufficient action and undertake this endeavor. But we have an overriding responsibility to be prepared if we fail to meet the Paris agreement’s targets. That means considering all potential responses that could minimize the damage and suffering to people and the planet.