Celeste Saulo, WMO Secretary-General: ‘The global warming indicators are alarming’

The World Meteorological Organization (WMO) presented its 2024 State of the Global Climate report on Wednesday, analyzing key indicators of a climate crisis affecting the entire planet. In this videoconference interview, WMO Secretary-General Celeste Saulo, 60, discusses the report’s key findings, highlighting that 2024 was the warmest year on record. Moreover, the report examines the growing impacts that global warming is having on the planet. In this context, as scientific evidence continues to mount, populist climate change denialism is gaining traction worldwide, fueled by figures such as Donald Trump and Javier Milei.

Question. 2024 was a record-breaking year for heat, as well as for the concentration of greenhouse gases in the atmosphere. Is it possible to separate these two issues?

Answer. Science has clearly shown us that greenhouse gases are largely responsible for the global warming we are seeing. And there is precise and robust documentation on this: unfortunately, it is human action that is causing this warming.

Q. However, there are voices that still disconnect both issues.

A. Yes, but as a science- and technology-based organization, the WMO relies on data, scientific evidence, and published work from around the world. The IPCC, which conducts the assessments, has been very clear on this matter. There may always be dissenting voices, but they are isolated. The scientific consensus is clear, and as an organization, we stand firmly on the side of that consensus.

Q. In other words, this report is not about politics — it is about science.

A. Yes, absolutely. Science has provided us with many tools to improve our lives and to better understand the planet we live on. And in this particular case, science is warning us about what is happening with the climate through the global monitoring efforts we coordinate — though it is the individual countries that conduct these observations. This is something worth emphasizing: the data used in this assessment come from the countries themselves, generated by their own national meteorological and hydrological services.

Q. Is the record heat of 2024 an exception or part of a trend?

A. Unfortunately, it’s a trend. Since the 1960s, the trend has clearly been toward temperature anomalies, which are growing. In our report, we highlight that each of the past 10 years has individually been a record high in relative temperatures.

Q. But the report also points out some factors that may have influenced the extraordinary results of 2023 and 2024, in addition to greenhouse gases, which are the main cause of warming.

A. Exactly, we always talk about climate variability because it’s a reality and something the WMO is working on a lot. One of the major drivers of climate variability is the El Niño phenomenon, and of course, when El Niño is active, higher temperatures tend to be recorded, mainly in the Northern Hemisphere.

Q. And could 2025 set another record without the presence of El Niño?

A. In principle, experts point out that a record shouldn’t be expected, but the system is immersed in a warming trend. In any case, records are like wake-up calls, they’re like sirens. The trend is the underlying concern, which is important to highlight. I think 2024 serves as a siren.

Q. Because climate change is much more than record average temperatures, right?

A. Of course, and we pointed this out in our report. There are many indicators, and all of them — absolutely all of them — are worrying. Those that measure the state of the oceans, whether it’s sea level rise, ocean heat content, or water acidification. Or the melting of glaciers, or the surface area of ice in the Arctic and Antarctic. Or the number of extreme events... We’re measuring many indicators, and this isn’t an isolated event because they all point in the same direction and respond to the same physical phenomenon, which is warming, sustained warming caused by greenhouse gases.

Q. Wherever you look, climate change rears its ugly head.

A. Exactly. We also know that some indicators are more worrying than others, such as the rising sea level for small island states. Or ocean acidification when we talk about ecosystems. Or heatwaves when we talk about health.

Q. Are we at the point where the signs of climate change are at their clearest?

A. Absolutely. It’s a little difficult to explain to anyone what a temperature anomaly of 1.55 degrees above pre-industrial levels means. Most people will say: what is that? That’s why our report documents extreme events. That’s what people feel. It’s what less developed and more developed countries experience, although with different consequences due to their response and recovery capacity. What the report seeks to do is relate a somewhat abstract variable with concrete facts of reality that affected absolutely the entire planet. There isn’t a single place on the planet, no continent, where it can be said that nothing happened here. From Antarctica to North America, even the small island states in the Pacific... Absolutely everyone was impacted by some extreme event that was extraordinary for what their official records indicate.

Q. Don’t you find it difficult to understand that, in this context, there is a rise of populist climate change denialism around the world?

A. Yes, the reality is that it’s difficult to understand. But it’s not the WMO’s place to get involved in that area. Our job is to present the evidence, and that is the role we will continue to play, as we have historically.

Q. You emphasize that the data comes from the countries themselves, from national meteorological services. Are you concerned that with Trump’s return to the White House, federal agencies could stop sharing information with the WMO?

A. I hope that doesn’t happen. The WMO is commemorating its 75th anniversary within the U.N. system this year, but we’ve been an organization for 152 years. And how has something survived for 152 years? Because of countries’ understanding of the importance of sharing meteorological data. Because weather and climate do not recognize geographical boundaries. Air circulation phenomena move across regions. There was an early understanding, 152 years ago, that if information wasn’t shared, it would be a disadvantage for the countries. For example, I come from Argentina, and a cold front that starts affecting Chile will eventually affect Argentina, then quickly reach Uruguay, and eventually Brazil. Without a data-sharing system, one would be left highly exposed and unable to prevent, protect the population, and take action. The idea of exchanging information is very old, and it has survived all kinds of situations and global crises.

Q. Argentine President Javier Milei, in addition to being skeptical about climate change, withdrew the Argentine delegation from the last climate summit. What is your opinion of that step?

A. These are the country’s sovereign decisions that I hope can be reflected upon in light of what is happening. For example, Argentina recently suffered terrible flooding in the city of Bahía Blanca, where 16 people were killed. Studies by Argentine colleagues and around the world show that some areas in central and eastern Argentina are more vulnerable to climate change. And this is part of that picture. I hope the information reaches the levels it needs to reach so that the country is better prepared. The countries that prepare best will be those that have the potential to even find opportunities in a changing climate. And denying the possibility to be prepared, I believe, does not help.

Q. In 2024, the 1.5 degree Celsius threshold relative to pre-industrial levels was surpassed for the first time in an official year. Can we now consider the Paris Agreement to have been breached?

A. No, because the Paris Agreement uses 20-year temperature averages as its reference point. One year doesn’t make a 20-year average. But what it does do is sound the alarm on a trend that is irreversibly moving upward.

Q. What messages should society take away from the 2024 State of the Global Climate report?

A. I think we have to keep in mind that the indicators are alarming, because they all consistently point to a worsening situation — whether in greenhouse gas emissions, melting glaciers, rising temperatures, or the number of extreme events. But, in addition, all these climate physics indicators translate into impacts on people and societies. These impacts translate into health, food security, access to water, all kinds of problems related to development and well-being. We have to make that connection between what happens in a physical system like the climate and what happens to us as individuals living in a globalized society.

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