Heat-trapping carbon dioxide levels in the atmosphere soared by the highest amount ever recorded in 2024, reaching levels unseen in human civilization and triggering urgent warnings from the World Meteorological Organization (WMO). According to the WMO’s latest Greenhouse Gas Bulletin, released just ahead of the United Nations’ annual climate conference, the spike in carbon dioxide (CO2) concentrations is not only committing the planet to more long-term warming but is also fueling a cascade of extreme weather events and raising fresh doubts about the world’s ability to meet key climate goals.
The WMO, a specialized agency of the United Nations responsible for international cooperation in atmospheric science, meteorology, and climate monitoring, reported that the global average concentration of CO2 surged by 3.5 parts per million (ppm) from 2023 to 2024. This is the largest annual increase since modern measurements began in 1957, as reported by BBC and the Associated Press. The current CO2 level now stands at 423.9 ppm, a staggering 50% higher than pre-industrial levels of around 280 ppm. To put this in perspective, when the WMO’s Greenhouse Gas Bulletin was first published in 2004, the CO2 level was 377.1 ppm.
The relentless rise in CO2, the principal greenhouse gas responsible for about three-quarters of planet-warming emissions, is primarily driven by human activities such as the burning of fossil fuels, land-use changes, and industrial processes like cement production. However, 2024’s record jump was also fueled by an upsurge in wildfires and a reduced capacity of the planet’s natural carbon sinks—forests and oceans—to absorb CO2. The year 2024 was the warmest ever recorded, marked by a powerful El Niño event, exceptional drought, and devastating fires in regions like the Amazon and southern Africa.
“The heat trapped by CO2 and other greenhouse gases is turbo-charging our climate and leading to more extreme weather. Reducing emissions is therefore essential not just for our climate but also for our economic security and community well-being,” said Ko Barrett, WMO Deputy Secretary-General, in a statement cited by Reuters and the Associated Press. The WMO’s findings underscore that today’s CO2 emissions will impact global climate not only now but for hundreds of years due to the gas’s long atmospheric lifetime.
Growth rates of CO2 have tripled since the 1960s, accelerating from an annual average increase of 0.8 ppm per year to 2.4 ppm per year in the decade from 2011 to 2020. The sharpest jump came between 2023 and 2024, with a 3.5 ppm increase. About half of all CO2 emitted each year remains in the atmosphere, while the rest is absorbed by land ecosystems and oceans. Yet, this storage is not permanent. As Oksana Tarasova, a senior scientific officer at the WMO, explained, “There is concern that terrestrial and ocean CO2 sinks are becoming less effective, which will increase the amount of CO2 that stays in the atmosphere, thereby accelerating global warming.”
Scientists are particularly worried that global warming is reducing the absorption capacity of these crucial sinks. Forests are becoming drier and more prone to wildfires, while warming ocean waters hold less dissolved gas. During El Niño years, such as 2024, the efficiency of land carbon sinks diminishes due to drier vegetation and increased forest fires. This creates a vicious climate cycle: as the planet warms, natural carbon sinks become less effective, leading to even higher atmospheric CO2 levels and further warming.
The WMO also reported that concentrations of methane and nitrous oxide—the second and third most important long-lived greenhouse gases linked to human activity—have reached record levels. Methane, though making up only a minuscule fraction of the atmosphere, is responsible for about 25% of global warming and has a global average concentration of 1,942 parts per billion (ppb) in 2024, an increase of 166% above pre-industrial levels. About 60% of methane emissions come from human sources, including fossil fuel leaks, landfills, livestock, rice farming, and biomass burning. The remaining 40% comes from natural sources such as wetlands and wildfires.
Nitrous oxide, mainly associated with the use of nitrogen fertilizer and manure from agricultural expansion and intensification, reached 338.0 ppb in 2024, which is 25% higher than pre-industrial levels. Both gases, like CO2, have long atmospheric lifetimes and contribute significantly to the planet’s greenhouse effect.
Bill Hare, CEO of Climate Analytics, called the new data “alarming and worrying.” He noted that even though fossil fuel emissions were “relatively flat” last year, the report showed an accelerating increase of CO2 in the atmosphere, “signalling a positive feedback from burning forests and warming oceans driven by record global temperatures.” Hare warned, “Let there be no mistake, this is a very clear warning sign that the world is heading into an extremely dangerous state—and this is driven by the continued expansion of fossil fuel development, globally. I’m beginning to feel that this points to a slow-moving climate catastrophe unfolding in front of us.”
The latest WMO report was released as a scientific resource ahead of the UN Climate Change Conference (COP30), set to take place in Belém, Brazil, in November 2025. The timing is critical: the world is already struggling to stay on track to meet the Paris Agreement’s goal of limiting global warming to 1.5 degrees Celsius above pre-industrial levels. United Nations climate chief Simon Stiell has warned that, at the current rate, the Earth is on course for a 3-degree Celsius increase—a scenario with potentially catastrophic consequences for ecosystems and societies worldwide.
The WMO emphasized the need for sustained and expanded greenhouse gas monitoring to inform effective climate action. “Sustaining and expanding greenhouse gas monitoring are critical to support such efforts,” said Oksana Tarasova, highlighting the role of scientific data in guiding policy and international negotiations. The organization’s Global Atmosphere Watch Programme coordinates systematic observations and analysis of greenhouse gases, with data archived and distributed by the World Data Centre for Greenhouse Gases at the Japan Meteorological Agency.
Meanwhile, the U.S. National Oceanic and Atmospheric Administration’s global data for 2025 through June indicate that carbon dioxide rates are still rising at one of the highest rates on record, though not quite as high as the previous year. The agency’s monitoring at Hawaii’s Mauna Loa Observatory confirms that CO2 concentrations continue to climb, underscoring the persistent challenge of reducing emissions.
As governments, industries, and communities grapple with the implications of these findings, the WMO’s message is clear: the world is at a crossroads. Without rapid, concerted action to curb greenhouse gas emissions and enhance the resilience of carbon sinks, the risk of a “slow-moving climate catastrophe” grows ever more real. The data may be daunting, but the choice—action or inaction—remains ours to make.
