> A primary hypothesized reason for the literally-off-the-charts heat of the past 15 months or so is that regulations that cleaned up the amount of sunlight-ref

> A primary hypothesized reason for the literally-off-the-charts heat of the past 15 months or so is that regulations that cleaned up the amount of sunlight-reflecting aerosols in container ship fuel was having the effect of letting more sunlight reach Earth; the idea is that the aerosols had previously been limiting the amount of global warming that would have shown up earlier. I see this repeated a lot on HN, but it appears to be incorrect. It seems that climate scientists are aware of aerosols and can model them, but 2023 is still a baffling outlier. > These include continued accumulation of greenhouse gases, the evolution of El Niña and La Niña, and the 11-year solar cycle. It also includes two new factors that emerged during the decade: the 2022 eruption of the Hunga Tonga volcano and the 2020 phase-out of sulphur in marine fuels. Both of these are estimated to have relatively modest effects at present – less than 0.05C each – but with large scientific uncertainties. > Similarly, the phase-out of sulphur in marine fuels occurred in 2020. If it had a large climate impact, it would show up in 2021 and 2022 rather than suddenly affecting the record in 2023. While it definitely has had a climate impact – alongside the broader reduction in aerosol emissions over the past three decades – the timing suggests that its likely not the primary driver of 2023 extremes. https://www.theclimatebrink.com/p/2023s-unexpected-and-unexplained https://www.theclimatebrink.com/p/2023s-unexpected-and-unexp...