Albedo worry

In Science magazine, this abstract:

In 2023, the global mean temperature soared to almost 1.5K above the pre-industrial level, surpassing the previous record by about 0.17K. Previous best-guess estimates of known drivers including anthropogenic warming and the El Niño onset fall short by about 0.2K in explaining the temperature rise. Utilizing satellite and reanalysis data, we identify a record-low planetary albedo as the primary factor bridging this gap. The decline is apparently caused largely by a reduced low-cloud cover in the northern mid-latitudes and tropics, in continuation of a multi-annual trend. Further exploring the low-cloud trend and understanding how much of it is due to internal variability, reduced aerosol concentrations, or a possibly emerging low-cloud feedback will be crucial for assessing the current and expected future warming.

Of course, how to work out the net effect of clouds has been one of the main bugbears of climate modelling.  The skeptic hope was that higher temperatures would mean more cloud and more albedo to keep the earth from getting too hot.  (I thought that was how the late Richard Lindzen's iris effect idea worked, but now that I double check, it was more that cirrus clouds would reduce and allow more IR to escape - so I'm not sure if an increase of lower, brighter clouds was actually part of that theory or not.)  

Anyhow - it remains a major worry that it is unclear whether the modelling has got the cloud effects underestimated, so that global temperature increases could be more rapid than expected.

Gavin Schmidt at Real Climate has a brief commentary on the paper here.  There is quite a bit of talk in the comments following about whether to credit reduced sulphur emissions from shipping as causing the albedo decrease, too.