Tiens je découvre l’assombrissement global (global dimming). Je m’étonne d’être passé à côté de cet aspect du climat (ou je n’ai pas bonne mémoire).
– ▻https://en.wikipedia.org/wiki/Global_dimming
– ▻https://fr.wikipedia.org/wiki/Assombrissement_global
Pour la faire courte : les incendies, chauffages et transports (en gros la combustion de combustible fossile) émettent des particules qui obscurcissent le ciel (réduisent les rayonnements solaire à la surface) (mesurable depuis les années 1950)… ce qui — parmi différentes choses (notamment pas bonnes pour la santé) — a réduit un peu le réchauffement climatique. Le paradoxe est donc que pour limiter le réchauffement climatique (et améliorer la santé), il faut moins émettre ces aérosols… ce qui va éclaircir le ciel (et donc provoquer aussi un réchauffement en passant) :
Some scientists now consider that the effects of global dimming have significantly masked the effect of global warming and that resolving global dimming may therefore lead to increases in future temperature rise.
According to Beate Liepert, “We lived in a global warming plus a global dimming world and now we are taking out global dimming. So we end up with the global warming world, which will be much worse than we thought it will be, much hotter.”
The magnitude of this masking effect is one of the central problems in current climate change with significant implications for future climate changes and policy responses to global warming.
#climat #global_dimming #global_brightening #assombrissement_global #éclaircissement_global
En relation cet article de mars 2022 : ▻https://www.eumetsat.int/more-sunshine-in-europe-due-to-cleaner-air qui contient quelques graphiques.
More sunshine in Europe due to cleaner air
How satellite-based climate data records support our understanding of the impact of cleaner air on the Earth’s climate.
[...]
In fact, increases of aerosol concentration are known to affect the clouds in various ways.
Firstly, they lead to clouds with smaller droplets and higher brightness (referred to as the first indirect aerosol effect; Twomey, 1977).
Secondly, they lead to clouds having a longer life time, a higher thickness, and less precipitation (referred as the second in-direct aerosol effect; Albrecht, 1989). Figure 2 illustrates the direct and indirect aerosol effects.
[...]
In its 6th Assessment Report, the International Panel for Climate Change (IPCC, 2021) states with high confidence, that the reduced aerosol concentrations in the recent decades led to an observable positive trend in shortwave radiation over Europe. As an unfavourable side effect, improved air quality (less aerosols) enhances warming through the direct and in-direct aerosol effects.