Even if we overshoot the 1.5C limit set by the Paris Agreement, we must return to it as quickly as possible.
The world is burning and our political leaders are failing us. With temperatures rising at an alarming rate, it seems that anyone who believes it is still possible to limit global heating to 1.5C from pre-industrial times is in a rapidly shrinking minority.
As governments around the world fail to meet their responsibilities under the Paris climate agreement, the window for keeping global temperatures below the 1.5C limit has all but closed due to insufficient action. But while some eminent commentators have declared the ceiling ‘deader than a doornail’, it will never die.
A dire state
To be sure, the world is in a dire state. Greenhouse-gas (GHG) emissions dumped in the atmosphere since the start of the industrial revolution have already warmed the planet by roughly 1.3C, according to this year’s annual report on Indicators of Global Climate Change. And studies, including mine, unequivocally show that crucial climate goals are not being met. Under current policies, global temperatures are projected to increase by 2.5-3C by the end of this century.
Even if governments meet all their existing climate pledges, the odds against global heating staying below 1.5C are seven to one. Combine this with the fossil-fuel industry’s delaying tactics, including the greenwashing of its polluting business practices and recent rollback on self-imposed emissions targets, and it becomes abundantly clear that our chances of staying within the limit are indeed slim. Consequently, climate scientists expect global warming to ‘blast past’ it.
But just as risks do not vanish when safety limits are exceeded, the Paris Agreement’s climate commitments do not disappear once we cross 1.5C. While it is a political ceiling, it was not pulled out of thin air. It is a scientifically informed limit, first championed by small-island states and later supported by a broad coalition of ambitious countries.
By now, it is clear to many governments that allowing global heating to exceed 1.5C involves unacceptable societal risks, undermines development and poses an existential threat to vulnerable communities and their cultures. Moreover, the line between ‘safe’ and ‘dangerous’ warming is becoming increasingly blurred. As the devastating effects of climate change worldwide show, even 1.5C is dangerous and our societies are ill-equipped to handle it.
Over the past 20 years, we have experienced what a world that has warmed by about 1C is like. No region has been spared the impact, with a growing number of countries facing fires, floods and storms, resulting in devastating human and financial costs which extend well beyond national borders. Between 2000 and 2019, climate-related disasters claimed over half a million lives, caused over $2 trillion in estimated damage, and affected almost four billion people worldwide.
Even at 1.5C warming, up to one in seven species face extinction, critical ecosystems such as tropical coral reefs face destruction and extreme heatwaves that our great-grandparents experienced once in a lifetime will occur on average every six years. Centuries of ice melt will cause sea levels to rise, flooding major cities such as London, New York, Shanghai and Kolkata. Vulnerable and marginalised communities’ efforts to escape poverty will be undermined and every country’s economic development will be impeded.
Matter of social justice
Limiting global heating is thus a matter of social justice, human rights and long-term development, and this imperative remains even if we cross the 1.5C threshold. Moreover, while exceeding it will have unpredictable political consequences as compensation claims for avoidable climate-related damage increase, the political implications of reducing GHG emissions remain consistent with what the Paris Agreement already outlines.
To halt global heating, the agreement expects countries to implement emissions-reduction plans that represent their ‘highest possible ambition’. While governments are failing to meet this goal, exceeding 1.5C does not change their responsibilities; in fact, fulfilling these commitments will become more important as temperatures continue to rise. The only way to improve our chances of keeping warming close to the limit is by pledging and implementing more ambitious near-term emission cuts every year until 2035.
Even if we cannot avoid overshooting, the threshold remains relevant. Every fraction of a degree counts and global climate efforts must therefore focus on limiting the exceedance of 1.5C and returning to safe levels as quickly as possible. The Paris agreement’s target of achieving global net-zero GHG emissions, in particular, could help reverse some of the excess warming. To maintain a safe, liveable and just planet, we must keep our eyes on the 1.5C limit and ensure that pursuing it remains our priority.
Republication forbidden—copyright Project Syndicate 2024, ‘The 1.5°C target for global warming must prevail’
Joeri Rogelj is professor of climate science and policy at the Grantham Institute for Climate Change and the Environment at Imperial College London. He is a lead author of reports of the Intergovernmental Panel on Climate Change and the United Nations Environment Programme.