COP30 will have to be the most important of all climate conferences, says Carlos Nobre

The climate scientist was the first scientific coordinator of the Large-Scale Biosphere-Atmosphere Experiment in the Amazon (LBA).

By Elton Alisson  |  Agência FAPESP – The 30th United Nations Climate Change Conference (COP30), to be held from November 10 to 21 in Belém, Pará, must be the most important COP in terms of advancing effective climate change mitigation efforts, according to Carlos Nobre, one of the world’s leading climate scientists.

Nobre is a senior researcher at the Institute of Advanced Studies at the University of São Paulo (IEA-USP) and co-chair of the Scientific Panel for the Amazon. In an interview with Agência FAPESP, he emphasized the need for all countries to reduce their greenhouse gas emissions to mitigate the risk of exceeding a 2 °C temperature increase by 2050.

“If we reach 2050 with 2 °C or, even worse, 2.5 °C warming, we’ll trigger several tipping points,” the scientist estimated, warning that, in this scenario, the Amazon would cease functioning as a forest and emit more carbon than it absorbs.

Nobre, the first scientific coordinator of the Large-Scale Biosphere-Atmosphere Experiment in the Amazon (LBA), believes that the initiative has been the world’s largest scientific project in a tropical forest and ushered in an era of large-scale experiments and multi-user research infrastructure in the Amazon Rainforest.

Agência FAPESP – What are your expectations for COP30?
Carlos Nobre – I have no doubt that this will have to be the most important of the 30 COPs. Without a doubt, the most important [so far] was the one that took place in 2015, COP21, in Paris. It was the first time that all countries presented their voluntary emission reduction targets, known as NDCs, or nationally determined contributions. In 2015, it was said: “We cannot, under any circumstances, allow the global temperature to rise more than 1 °C, ideally 1.5 °C, but not 2 °C.” And all countries committed to reducing emissions by 70% by 2050 and to zero emissions by 2100. But then a beautiful special report by the IPCC in 2018 showed that if the temperature rose above 1.5 °C, it would represent a huge risk of what we call tipping points. And what became very famous there, not least because the oceans were already getting warmer, was the extinction of coral reefs. It showed that if the temperature rises above 1.5 °C and reaches 2 °C, in the next century extinction will affect more than 99% of species in coral reefs, which maintain 25% of ocean biodiversity. COP26, held in Glasgow, Scotland, in 2021, was the second most important because all countries agreed not to let the temperature exceed 1.5 °C. To achieve this, science showed that it’d be necessary to reduce emissions by 43% by 2030 compared to 2019 emissions and to zero net emissions by 2050. However, until last year, we weren’t moving in that direction. The highest emissions were in 2024. This year, it’s unclear whether they’ll at least stabilize. In the first half of the year, they remained high, and we have to wait until the end of the year, but it seems very difficult to reduce emissions by 43% by 2030. Studies show that, with the targets that all countries have set in their NDCs – and, in fact, these studies were done before this American president was elected – we’d reduce emissions by up to 3% by 2030, not 43%. So the risk of going from 2 °C by 2050 to 2.5 °C is very high. Therefore, in my opinion, COP30, even without the presence of the United States – which from 1850 to the present has emitted the most, with 20% of all greenhouse gas emissions, and today is second, behind China, which is first – has to be, as COP21 was with the Paris Agreement, and then COP26, the most important COP. All countries, even if the United States isn’t involved, must greatly accelerate the reduction of emissions. It’s a huge challenge. China has set small reduction targets until 2035. It needs to accelerate significantly. Today, it’s the country that emits the most, along with India. The United States, on the other hand, has to wait for the next president to change this policy. During this president’s first term, from 2017 to 2020, emissions increased, and it’s almost certain that they’ll increase this year as well, and almost certainly every one of the other three years as well.

Agência FAPESP – And what are the risks?
Nobre – If we reach 2050 with 2 °C or, even worse, 2.5 °C warming, we’ll trigger several tipping points. Science today already knows of more than 20 tipping points. By the next century, there will be a major extinction of coral reefs and countless ocean species, but also species from the continents. There are already many species extinctions in the Amazon. If the temperature exceeds 2 °C warming, we’ll cause the frozen soil of Siberia, northern Canada, and northern Alaska, known as permafrost, to thaw. This permafrost froze millions and millions of years ago and has trapped a huge amount of greenhouse gases, such as methane, which is 28 to 30 times more powerful at retaining heat than carbon dioxide. And it’s already started to thaw. By 2100, more than 200 billion tons of these gases from the permafrost will be released into the atmosphere. We’re really going to accelerate the melting of the ice sheet in Greenland. This will greatly increase the level of the sea and also part of Western Antarctica. We’ll practically melt the ice in the Arctic Sea and in the ocean on the Antarctic side. And we’ll lose the Amazon. So COP30 has to be as important as COP21 was, with the Paris Agreement, and then COP26.

Agência FAPESP – Is a new agreement the solution?
Nobre – All countries must agree to significantly accelerate the reduction of emissions and at the same time, as was stated at COP29. Ambassador André Corrêa do Lago has already said that he’ll take this issue to COP30, which is the need for the approval of the green climate fund. It was a very small fund, with USD 100 billion until 2025. From 2026 to 2035, a study released at COP29 in Azerbaijan showed that this figure had to be USD 1.3 trillion, or about USD 800 billion per year until 2035, to super-accelerate the energy transition. Renewable energy is entirely feasible. Solar and wind power are already much cheaper. The biggest cause of urban pollution in the world is the burning of fossil fuels, coal, oil, and diesel. This leads to 6 to 7 million deaths per year due to urban pollution. In the city of São Paulo, Professor Paulo Saldiva, from USP [University of São Paulo], has been conducting studies for decades and has mapped the life expectancy of São Paulo residents and the entire metropolitan region of São Paulo, which is two to four years shorter due to pollution. So, these renewable energies will improve air quality and greatly reduce emissions. Thus, USD 800 billion per year is needed until 2035 to greatly improve adaptation capacity and increase resilience. We have more than 2 billion people in the world who are totally vulnerable to these extreme events – heat waves, droughts, forest fires, super rains, flooding, and landslides on the coast. So another USD 500 billion per year is needed to greatly improve adaptation capacity.

Agência FAPESP – Are there risks for Brazil?
Nobre – Here in Brazil, we have millions and millions of Brazilians living in areas at risk of heavy rains, as happened in [the state of] Rio Grande do Sul last year. A recent study by the science and technology adaptation committee in Rio Grande do Sul has already calculated that there are more than 500,000 people currently living in areas at risk of flooding and landslides on the coast. In Brazil, that number is certainly more than 4 million. CEMADEN [National Center for Monitoring and Early Warning of Natural Disasters] is conducting a study now, and did one in 2018, which pointed out that there are more than 2 million Brazilians at very high risk. This can’t continue. Just imagine how much money it takes to get these people out of these risk areas. And the extreme event that causes the most deaths isn’t heavy rains, but heat waves, which cause many, many more deaths. Studies are beginning to indicate more than 500,000 deaths per year worldwide. Here in Brazil, there are also a large number of deaths. We had a record number of heat waves in 2023, but mainly in 2024 and early 2025. So, adapting to heat waves is quite complex. For example, a city like Barcelona, after the heat waves of 2022 and 2023, created a lot of places with swimming pools, air conditioning, doctors, and all older adults, babies, and sick people are mapped. And when the weather forecast predicts a very strong heat wave, these people are invited to stay there for days until the heat wave is over. This is one form of adaptation. Another very important adaptation is urban forest restoration. When you plant a lot of trees, you lower the maximum temperature by a few degrees, for example, in Greater São Paulo – or even more than 5 °C. Forest restoration also removes 20% to 30% of pollutants, keeping the climate under the trees much healthier. The greenest city in the world is Singapore. Everyone grows plants on their roofs, on top of all buildings, on their balconies. This lowers the temperature considerably. We don’t have this habit in Brazil.

Agência FAPESP – You were the first scientific coordinator of the LBA. How did the initiative to create and implement the experiment come about?
Nobre – I was involved from the beginning of what later became the Large-Scale Biosphere-Atmosphere Experiment in the Amazon, which we named the LBA experiment. The first meeting where we began to discuss the importance of having a large-scale experiment in the Amazon was in November 1993. I’d spent a year at the University of Maryland in the United States and met several researchers – including [Piers] Sellers [1955–2016], who worked at NASA [the US space agency] and became an astronaut – as well as Professor [Jagadish] Shukla. I’d also been working closely with the UK Centre for Ecology and Hydrology, located in the city of Wallingford [in England]. As part of this hydrology research, we’d already installed instruments to measure how the forest and pasture interact with the atmosphere. We started this experiment with two towers, one in the forest and the other in a pasture area. The first was installed in 1990, a little north of Manaus [in Brazil], and the second in southern Pará [Brazilian state located in the Amazon], in Marabá. In the same year, a third tower was installed in [the state of] Rondônia. And at a meeting at NASA in November 1993, we brought these people together and said, “We have to create a large-scale experiment for the Amazon.” Starting in 1994, we began to discuss this, bringing together scientists from the Amazon – from various Amazonian countries – as well as from the United States and six European countries. Then we held a meeting in São José dos Campos [São Paulo state] in August 1996 and approved a complete proposal. In August 1998, we began setting up the entire experiment, and it actually began operating in January 1999. We then quickly set up a series of measurement sites. In partnership with the British, we already had three sites with towers equipped with a series of instruments that measured how the forest exchanges heat, water vapor, and carbon dioxide, and we did this from the top of the forest to the ground and pastures. In less than two years, we already had 25 sites with towers, including some in the Cerrado [the Brazilian savanna-like bioma]. We also formed several partnerships with research aircraft from the United States, from institutions such as NASA and NOAA [the National Oceanic and Atmospheric Administration, a scientific agency linked to the U.S. Department of Commerce], as well as Great Britain and INPE [Brazil’s National Institute for Space Research]. These aircraft took a series of measurements, covering the entire Amazon Rainforest. A little north of Belém, near the ocean, an experiment was set up in which most of the rainwater was blocked to assess how many trees wouldn’t survive if the Amazon’s climate changed, because in 1990 and 1991 I’d published the first two articles in which I used the term “savannization” of the Amazon. If there were too much deforestation, we’d pass the tipping point. Much of the Amazon would become savannized, with few trees. So, the experiment was to see which trees would survive, and this study continues today, involving many countries. It was the largest rainforest experiment conducted at that time and continues today. Of course, the number of measurement points has decreased significantly, but the experiment continues.

Agência FAPESP – Has the LBA already pointed to a tipping point?
Nobre – When I was working at the Ministry of Science and Technology between 2011 and 2014, where I was the secretary [for national research and development policy], we worked hard to get approval for a partnership with Germany, with the Max Planck Institute, and a 325-meter-high tower was built north of Manaus [the Amazon Tall Tower Observatory, ATTO], which still exists today. It’s a tower that’s enabling countless valuable experiments on what’s happening in the Amazon on a grand scale because the wind that comes from thousands of kilometers away passes through there, and they measure all the chemical compounds and everything else to find out what’s happening, whether the Amazon is very close to a tipping point. And the LBA experiment was the one that showed this the most, because several studies from the experiment showed that throughout the southern Amazon region, from the Atlantic to Bolivia, passing through the plains of Colombia and Peru, the dry season is already four to five weeks longer than it was 40 or 45 years ago. That’s one week per decade. Luciana Gatti, from INPE, began taking measurements between 2008 and 2009 throughout the Amazon at four points in the forest: southeast, northeast, northwest, and southwest. She used data from instruments and airplanes flying at altitudes of several kilometers to measure greenhouse gases, carbon dioxide, and carbon monoxide. And this experiment showed something very worrying. The first article, published in the journal Nature in 2021, showed that in the southeast of the Amazon, south of Pará and north of Mato Grosso, the forest has already become a source of carbon. Globally, all biomes in the world remove carbon dioxide. We currently emit almost 40 billion tons of carbon dioxide per year, but there’s also deforestation, and the forest has always removed a third of what we emit, otherwise the temperature would have exceeded 2 °C warming long ago. In the 1990s, the Amazon removed up to 1.5 billion tons per year. It’s decreased a lot. The Amazon has lost this capacity and now removes much less, a few hundred million tons today. In that area, that is, the southeastern Amazon, south of Pará and north of Mato Grosso, the forest has become a source of carbon since 2010, meaning that the forest loses carbon. Other studies from the LBA experiment also showed a huge increase in tree mortality across much of the Amazon. So, in a way, the LBA showed that we’re very close to the tipping point. Through the experiment, it was also possible to train more than 1,500 master’s and doctoral students in all Amazonian countries, as well as outside the Amazon, in the United States and European countries, and to publish more than 2,500 scientific articles.

Agência FAPESP – So, in a way, did the LBA usher in a phase of large-scale experiments and multi-user research infrastructure in the Amazon?
Nobre – Without a doubt. Of course, the LBA was created largely to understand the risk that the Amazon had and still has of passing the tipping point, but it was also very complementary [in relation to other issues]. It looked closely at how global warming, deforestation, and degradation affect biodiversity, both terrestrial and fluvial. The Amazon recycles water very well. About 45% of all the water vapor that enters the Amazon basin from the Atlantic Ocean doesn’t return to the Atlantic via the Amazon River. It moves slightly southward, toward the Andes. Much of it comes south and accounts for much of the rainfall in the Cerrado, as well as 15% of the rainfall in the Southeast, much of the rainfall in the South, Uruguay, Paraguay, northern Argentina, and the maintenance of the Atlantic Forest. So these are ecosystem services, the result of tens of millions of years of evolution, and they’re very important. The LBA experiment looked at all of this and, more recently, the ATTO tower showed the great importance of the forest as a whole, the disruption that deforestation, burning, and degradation are causing, and how efficient the forest is at recycling water. And AmazonFACE will tell us whether, if we continue to release these gases into the atmosphere, we’ll reach 560 parts per million before 2100. Will the forest play a major role in helping to combat this by removing a lot of carbon dioxide, or not? Will soil nutrient problems prevent the forest from being very efficient?

Agência FAPESP – Have the impacts of the cuts in U.S. funding for science already been felt in these collaborations with Brazil in climate science?
Nobre – The partners in the LBA experiment are already feeling the cost of the budget cuts that several universities and institutions have suffered. The United States was the country that contributed the most in terms of scientific collaboration, financial support, researcher participation, and infrastructure. Most of the research aircraft came from there. And now we’ll see what happens, because four years with a denialist president like this one and budget cuts for several partners who remain in the LBA could have an impact. But fortunately, Brazil has also taken on a very important leadership role.

Watch the full interview with Carlos Nobre at the FAPESP Memory Center.