Climate still in the red: three levers for action

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Despite the slowdown in global greenhouse gas (GHG) emissions, climate indicators remain in the red, as the recently published Indicators of Global Climate Change 2024 report reminds us. This report also identifies three levers of action to be implemented to stabilize the atmospheric stock of GHGs that cause global warming.

The virtual world of social media is one of immediacy. A TikTok user spends an average of 95 minutes browsing each day, generating hundreds of clicks. In politics, the populist wave is riding this continuous stream of information that floods our daily lives.

In these virtual worlds, decisions are made based on the vagaries of the moment, even if it means quickly reversing course in the event of unexpected reactions. Such submission to short-term moods is incompatible with action in the face of global warming and the degradation of biodiversity.

◗ This article was originally published by The Conversation

The first antidote to the tyranny of the immediate must be science. This is why the Intergovernmental Panel on Climate Change (IPCC) plays such a pivotal role in climate action. Since 1990, the IPCC has published six assessment reports. These reports provide valuable benchmarks, documenting the state of scientific knowledge on the climate system, the impacts and possible adaptations to global warming, and the mitigation levers to stabilize it.

However, the time spent navigating between two beacons is tending to increase. From five years between the first and second IPCC reports, it has increased to nine years between the last two reports. To prevent decision-makers from getting lost along the way, a collective of researchers publishes an annual dashboard each year, incorporating the methodologies used by the IPCC.

I read their report on the year 2024, released on June 17, 2025. Here is what I took away from it.

Red lights, despite the slowdown in emissions

The annual dashboard first updates information on CO₂ emissions through 2024 (and through 2023 for other greenhouse gases). Unsurprisingly, this update confirms the slowdown in the increase in global emissions observed over the past 15 years, mainly caused by _CO2 emissions.

This slowdown, however, is insufficient to stabilize or even slow the accumulation of GHG stocks in the atmosphere. The rate of growth of this stock is continuing, and has even accelerated for methane since the early 2020s.

Yet it is this stock that is the anthropogenic driver of global warming. It plays an even greater role as aerosol emissions (mainly sulfur dioxide), which have a short-term cooling effect on the planet, are reduced due to the tightening of restrictions on local pollutants, particularly in international shipping and in China.

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As a result, warming shows no sign of abating. It crossed the +1.5°C line for the first time in 2024. Anthropogenic factors accounted for 1.36°C of this increase, with the remainder attributed to natural climate variability, particularly the 2024 El Niño event.

Over the last ten recorded years, global warming has reached +1.24°C compared to the pre-industrial era. Over the ocean, it now exceeds 1°C. On land, it is 1.79°C, roughly equidistant between 1.5 and 2°C.

Unsurprisingly, continued global warming is fueling rising sea levels, driven by the thermal expansion of water and melting continental ice. The average ocean level has risen by an estimated 22.8 cm since the beginning of the last century. Between 2019 and 2024, it was 4.3 mm/year, well above the historical trend (1.8 mm/year).

To stabilize global warming, we must first drastically reduce fossil carbon emissions. As the Global Carbon Budget already noted in the fall of 2024, the remaining carbon budget for a 50/50 chance of limiting global warming to 2°C now represents only 28 years of current emissions. To target 1.5°C, that's now less than five years!

The dashboard also shows the impact of reducing aerosol emissions, which contribute significantly to global warming. Fewer aerosols in the atmosphere certainly means fewer health problems on land, but also more global warming because aerosols obscure solar radiation and affect cloud formation. However, since aerosols do not stay in the atmosphere for long, reducing their emissions quickly affects the volume of their stock in the atmosphere.

What can be done? The best way to counter this impact is to reduce methane emissions. Since methane has a shorter atmospheric lifetime than other greenhouse gases, reducing it has a significantly faster effect on global warming than an equivalent reduction in _CO2 or nitrous oxide, which stays in the atmosphere for an average of 120 years.

The dashboard finally highlights the emergence of climate "feedbacks" whose effects are added to the direct impact of anthropogenic emissions on temperature. For example, global warming stimulates methane emissions in tropical wetlands and risks, in the future, accentuating those resulting from the melting of permafrost. Combined with droughts, it also increases emissions generated by mega-forest fires and alters the growth capacity of trees, making them more vulnerable to pests.

In both cases, these feedbacks amplify warming. Acting against these feedbacks, for example by adapting forest management strategies, therefore responds to a dual logic of adaptation and mitigation of climate change.

While the dashboard aims to closely match the methods used in IPCC assessment reports, it also provides useful additions. I particularly appreciated the information on emissions from megafires, fluorinated gases, and the absorption of atmospheric _CO2 by cement.

The figure above shows three ways to account for global GHG emissions.

• At 55.4 billion tonnes (Gt) of _CO2 equivalent, the first bar shows the emissions for the year 2023 and the associated margin of uncertainty, calculated according to the standards adopted by the IPCC.
• Aggregating national inventory data collected on the United Nations website yields emissions of only 47.1 Gt for the same year. The difference between the two figures is mainly related to how emissions from land-use changes are accounted for, particularly the boundary between emissions and removals of anthropogenic origin and those of natural origin. For example, carbon stored through tree replanting is clearly of anthropogenic origin, but should carbon resulting from natural tree regrowth after fires also be included?
• The middle figure is an innovation in the dashboard, which has expanded the _CO2 sources and removals taken into account, resulting in total emissions of 56.9 Gt of _CO2 equivalent (+1.5 Gt compared to the standard assessment). Taking into account carbon sequestration by cement structures (cement "carbonation" ) represents a carbon sink of 0.8 Gt of _CO2 . But this is more than offset by methane and nitrous oxide emissions from forest fires and biomass combustion (1 Gt of _CO2 equivalent) and those from CFCs and other fluorinated gases not covered by the climate convention (UNFCCC), amounting to 1.3 Gt of _CO2 equivalent in 2023.

In the recent period, emissions of fluorinated gases (F-gases) listed under the UNFCC exceed those of fluorinated gases, the regulation of which was put in place by the Montreal Protocol (1987) intended to protect the ozone layer. But this situation is relatively recent. When the fight to protect the ozone layer began, emissions of CFCs and other fluorinated gases destroying this layer caused a warming equivalent to almost 12 Gt of CO ₂ , or half of the fossil carbon emissions at the time (22 Gt of CO ₂ equivalent).

The dramatic reduction in fluorinated gas emissions achieved to protect the ozone layer has thus had a major impact on climate action, despite the development of substitutes for these gases—such as HFCs—to meet air conditioning and refrigeration needs. This result is observed today in the decrease in the atmospheric concentration of CFCs, which contributes to mitigating global warming.

Given the atmospheric residence time of CFC gases, which is around half a century, this mitigation effect should continue for several decades. This is a good illustration of the inertia of stock versus flow, which is now beneficial for climate action in the case of fluorinated gases.

Conversely, this inertia is still pushing up the _CO2 and methane thermometer, despite the slowdown in emissions. Hence the red warning lights on the dashboard. Tomorrow, if we manage to sustainably reverse their emissions trajectory, this inertia could also push them down. But to do this, we must accelerate the low-carbon transition and not succumb to the lure of those who would like to backslide.

Christian de Perthuis, Professor of Economics, founder of the “Climate Economics” chair, Paris Dauphine University – PSL