Climate change is not a recent discovery: the physics of the greenhouse effect has been understood since 1824. What has changed is the scale of our emissions and the slowness of our response.
1.1The science: from Fourier to Arrhenius
In 1824, Joseph Fourier described how the atmosphere retains part of the Earth's heat. In 1859, John Tyndall measured in the laboratory that CO₂ and water vapour absorb infrared. In 1896, Svante Arrhenius was the first to calculate that a doubling of CO₂ would warm the planet by several degrees.
In other words, the core of climate theory was in place before 1900. Warming is not a recent hypothesis: it is a physical prediction more than a century old, since confirmed.
1.21958: the Keeling curve
In 1958, Charles Keeling began continuous measurement of atmospheric CO₂ at the summit of Mauna Loa, in Hawaii. His curve shows a steady rise: ~315 ppm in 1958, more than 420 ppm today, compared with ~280 ppm before the industrial era. It is the visual, irrefutable proof of accumulation.
1.31988-2015: the IPCC and climate diplomacy
In 1988 the IPCC (Intergovernmental Panel on Climate Change) was created, tasked with synthesising the science for decision-makers. Its sixth report (AR6, 2021-2023) remains the reference; the French paleoclimatologist Valérie Masson-Delmotte co-chaired its working group on the physical sciences.
Diplomacy followed: the Rio Summit (1992) and the creation of the UNFCCC, the Kyoto Protocol (1997), then the Paris Agreement (2015, COP21): aim for "well below 2 °C" and pursue 1.5 °C.
1.4Recent COPs: words, but little roadmap
- COP28 Dubai (2023): first mention of a "transition away from fossil fuels".
- COP29 Baku (2024): the "finance COP" and its new financing goal (NCQG).
- COP30 Belém (2025): a coalition of more than 80 countries on phasing out fossil fuels, but without a binding timetable.
1.5Energy history: a pile-up, not a replacement
Wood, then coal (the industrial revolution), then oil (the century of the car), then gas and nuclear: in France, the Messmer plan (1974) after the 1973 oil shock. Modern renewables took off in the 2010s. But each source was added to the previous ones: the world is still ~80% fossil-fuelled.
1824Fourier
The greenhouse effect is conceptualised.
1896Arrhenius
The first calculation of CO₂-driven warming.
1958Keeling
Continuous CO₂ measurement at Mauna Loa.
1988IPCC
Climate expertise becomes institutional.
2015Paris Agreement
Goal of "well below 2 °C".
2024+1.55 °C
First calendar year above 1.5 °C.
2025COP30 Belém
80+ countries on phasing out fossil fuels, with no timetable.
Key takeaway
Climate science is more than a hundred years old and its principle is not in dispute. The problem is not knowing, but acting: transforming a global energy system that is still 80% fossil.
Sources
IPCC, Sixth Assessment Report (AR6) (ipcc.ch); Scripps/NOAA, Keeling curve; UNFCCC, Kyoto and Paris agreements; energy history: V. Smil, Energy and Civilization.
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