Keep 1.5 within reach, "keep the 1.5 degrees within reach." This was the slogan with which COP28 opened, the United Nations conference on climate change that just concluded in Dubai. The feasibility of this goal, however, now seems more uncertain than ever, even though many considered this aim too ambitious from the outset. Already at last year's COP, doubts arose about the possibility of staying under 1.5 degrees. Over time, an increasing number of scientists argue that exceeding 1.5 degrees is becoming inevitable, as declared in 2022 by the same IPCC. 

It's no longer about staying under a certain temperature, but about managing to reverse some of the warming: the concept of climate overshoot comes into play, the difference between the peak temperatures we will reach and the lowest point to which we can return. Johan Rockström, president of The Earth League and director of the Potsdam Institute for Climate Impact Research, explained this during a press conference held at COP28. "In the best case scenario, in three or four decades we will have a warming of 1.8 degrees before returning to 1.5 at the end of this century," he said. "And to get back to 1.5 at the end of the century, everything has to be done right. Phasing out fossil fuels, transforming the global food system, maintaining all carbon wells and deposits, on land and in oceans, and implementing carbon dioxide removal."

In the scenarios envisaged to keep the global temperature increase below 1.5 degrees, a sharp reduction in the use of fossil fuels is foreseen. By 2050 coal consumption should be reduced by 95%, oil by 60%, and gas by 45%, but these targets conflict with the policies actually implemented. As the latest Global Carbon Budget shows, the global energy system is still heavily dependent on fossil fuels, and renewables, despite progress, still do not have a sufficient role.

Time is tight. The fact that there's no time to waste has often been reminded by Antonio Guterres, the United Nations Secretary-General. In April, he described the climate as “a time bomb ready to explode” and was echoed at the same time by Extinction Rebellion activists who, in Trieste's Piazza Unità d'Italia, drew a countdown on the ground. In less than seven years, they said, global temperatures will have risen by more than 1.5 degrees compared to pre-industrial levels. From that moment, it will no longer be possible to turn back. Numbers like these are essential to mark the pace of the climate crisis, to give us timelines on what awaits us, and to provide the necessary sense of urgency. They also set targets for governments to pursue. In the negotiations, the goal remained at the center of the debate, so much so that COP28 President Al Jaber called it “the guiding star” that had to guide states and companies in the agreements. So far, however, these ambitions have not been accompanied by the necessary emission reduction, which in the current state of commitments would lead to an increase of 2.5 degrees.

In reality, the time to stay below a 1.5 degree increase compared to pre-industrial temperatures has always been tight. This goal first appeared in 2009 in diplomatic agreements, and according to Mike Hulme, a human geographer at the University of Cambridge and one of the leading experts on social studies of the IPCC, 1.5 degrees were proposed for political reasons: "It was not a scientific discovery. No one discovered that 1.5 degrees was the threshold to stay under. It was the result of the mobilization of a variety of interests and political arguments." 

During the preparation of COP15 in 2009, the 2-degree target was already being considered, as described by researchers Béatrice Cointe and Hélène Guillemot in a study published in January 2023 for WIREs Climate Change. But during the conference in Copenhagen, the Least Developed Countries and the intergovernmental organization AOSIS, the Alliance of Small Island States - created specifically to give voice to the interests of countries vulnerable to climate change - raised their voices. They argued that reaching 2 degrees was too risky. Countries like the island nations face more severe risks with greater temperature increases.

A summary document, released in June 2015 after two years of dialogues between experts, invited parties to act precautionarily, as science was not yet clear on the real differences between the two goals. At the same time, however, the document noted that emission reduction was not proceeding according to plan: countries were behind and needed to act quickly. 2015 was also the year of COP21 and the Paris Agreements, which - after intense negotiations - adopted the 1.5 degree target. "1.5 or 2 degrees are precise metrics, but the idea of the Paris Agreements is to stay 'as close as possible': they were also chosen for their symbolic value. So, it's important to keep them as a goal and be aware that the climate crisis is not an on-off switch, success-failure," environmental journalist Ferdinando Cotugno told us in October.

Immediately after Paris, the target was met with surprise and skepticism by part of the scientific community, who considered the target unrealistic, especially because it did not correspond to a commensurate commitment on emission reduction. The politicians who pushed for the target, however, saw it as a success because it allowed the countries most vulnerable to climate change to breathe a sigh of relief.

The hesitation and controversy did not cease when the same COP21 called for a report to investigate the difference in impacts and paths between 1.5 and 2 degrees. The scientific community feared that this represented a political encroachment on science and an instrumental use of the IPCC to support political objectives. These tensions show how the goal, Hulme suggests, is an example of "policy-based evidence", which is the opposite of the more well-known "evidence-based policy". "Scientific evidence and political norms shape each other and there are no pure scientific proofs, just as perhaps there is no pure political norm."

Finally, in 2018, the evidence arrived: the IPCC's special report on the impacts of 1.5 degrees was released. It had an unprecedented media echo, with unprecedented coverage for the group's work. It also changed scientists' perceptions. Scientists began to consider research on 1.5-degree scenarios as legitimate and scientifically authoritative, report Cointe and Guillemot. Today it is well known that limiting warming to 1.5 degrees would reduce risks for the agri-food sector, for coral reefs, for sea level rise, and for the melting of Arctic and Antarctic ice.

After the release of the 2018 report, 1.5 degrees became cemented in the imagination as the ceiling not to be breached, the precipice not to lean over. The slogan became “We have 12 years to limit climate change catastrophe” (now, according to the Carbon clock, it has been reduced to 7 years to exceed). Scientists have often warned against a narrow interpretation of the target, which is sometimes considered as an expiration date after which climate risks become unsustainable. Jim Skea, then co-chair of the special report, explained it well in 2019, when he said that the report ‘‘did not establish that we have another twelve years to save the world. The warmer the climate gets, the worse it is, but there is no tipping point”.

Scientists and politicians have never stopped saying that, if we really want to avoid exceeding this threshold, what we are doing is not enough and requires a radical transformation of the global energy system.

A recent article published in Nature Communications analyzed the scenarios assessed by the IPCC compatible with 1.5 degrees of temperature or a slight and temporary overshoot of the threshold. Between 2020 and 2050, the supply of coal, oil, and gas should decrease on average by 95%, 62%, and 42%. According to the Paris Agreements, in the second half of this century, for every molecule of CO2 emitted, one will need to be removed from the air. And, since it is not possible to completely give up greenhouse gas emissions, technologies that remove carbon from the atmosphere are assumed to be used. However, many scenarios assume an amount of carbon capture and storage and removal technologies greater than what might be feasible. These technologies in recent years have been at the center of a heated debate in the scientific community. One of the most widespread criticisms is that they postpone the rapid and immediate mitigation needed, in the name of a future promise, and thus give room to the widespread consumption of fossil fuels. Even in the best scenario, however, "carbon capture and storage and the removal of atmospheric carbon dioxide will be necessary to mitigate and offset remaining emissions," reports the International Energy Agency. "Projects capable of capturing about 1.2 gigatonnes of CO2 by 2030 need to be realized, against the approximately 0.3 gigatonnes of CO2 currently projected for 2030". 

The technologies exist, work, and are under development. But the feasibility on a large scale and the acceptability of their widespread use is not certain: it would be a problem to depend on them if they then turn out to be insufficient or ineffective. Without carbon removal, instead, the supply of fossil fuels between 2020 and 2050 emissions should decrease in a even more drastic way: 99% for coal, 70% for oil, and 84% for gas.

What is happening is that the use of fossil fuels continues to increase, rather than  decrease in line with the pathways studied by the IPCC, and more and more scientists question the possibility of staying under 1.5 degrees. Yet in the negotiations, they still remain protagonists of the discussions and the agreements signed. "There is a tacit agreement to keep talking about these targets," suggests Hulme. "But in reality, we know we will exceed them.

Since man began measuring Earth's temperatures, June, July, and August have never been as hot as in 2023, as seen in recent records. In these three months, temperatures have exceeded the global average by 1.2 degrees. For a third of this year's days, the planet's temperature exceeded pre-industrial averages by over 1.5 degrees. And new records await us in the future. Everything suggests that temperatures will continue to rise and take us further away from the climate we know. Perhaps, in the next five or ten years there will be at least one year in which the global average temperature exceeds pre-industrial levels by 1.5 degrees. If this happens, “we must not despair and fall into a state of shock,” said Jim Skea last July to Der Spiegel. It will be a more dangerous world, but it won't be the end, and it's necessary to continue on the paths that lead us to confront the climate crisis. 

To break the Paris Agreements, it is not enough for the temperature threshold to be exceeded for a day or a week: we must look at measurements over the long term. However, there is still no agreement on which metric would be better to use to understand when we have exceeded 1.5 degrees, since the natural variability of the climate makes it difficult to precisely understand when the threshold is crossed. “Exceeding the limit once does not mean that the change is definitive. It is possible to get back below, the IPCC says it clearly,” says Ferdinando Cotugno. For now, in light of current political decisions and recorded emission rates, staying below 1.5 seems possible but not probable. 

Despite the growing loss of credibility of the target, even at COP28, the 1.5 degrees were at the center of the just-concluded negotiations. In particular, attention is on the First Global Stocktake, considered a historic document. For the first time, it is declared that to limit global warming, it's necessary to abandon (transitioning away) fossil fuels. In parallel, to stay below 1.5 degrees, other efforts are needed: tripling renewables by 2030 and using removal technologies for sectors that are hardest to decarbonize. In the coming months, it will be important to understand how these commitments will concretely translate into national plans.

One thing is certain: the gap between political ambitions and their feasibility will become increasingly difficult for governments to manage, as time is getting tighter. As journalist Emma Marris suggests, there is a possibility that 1.5 degrees: “will soon cease to be a target and become a historical fact.”

If this were to happen, as a part of the scientific community expects, what would happen to the negotiations? What consequences would abandoning such a deeply ingrained goal have? What matters, regardless of the global temperature fluctuations that await us, is that governments do not lose sight of the real goal: working for a world that is as habitable as possible. Ferdinando Cotugno said: “In a decade we might have this conversation again and know that we failed to stay below 1.5. But then we will say that we can still save 2 degrees. If we reach 1.5, then we must ensure we don't reach an increase of 2, 3, 4 degrees.” For now, we wait to see if the just-concluded COP really marks the moment when we start to leave fossil fuels behind.