14 Albedo
Dynes
Melting ice at the poles has reduced the world’s albedo from 29% to 28.6%, which might not sound like much but is equivalent to an extra 100 ppm of CO2 in the atmosphere. Both Antarctic & Arctic sea ice could virtually disappear in 2024. Albedo counts.
Hansen
Zeke Hausfather memorably termed the record September 2023 global temperature as “gobsmackingly bananas.” Subsequent monthly temperature anomalies have not been much smaller. These records coincide with a moderately strong El Nino, but they exceed expectations for even the strongest El Nino, if that were the only driving factor. Warming is also being driven by another factor, one that is ultimately more consequential: a large decrease of Earth’s albedo. In other words, Earth has become darker, absorbing more of the sunlight incident on the planet. The increase of absorbed solar radiation (1.4 W/m2) is a decrease of Earth’s albedo (reflectivity) of 0.4% (1.4/340). This reduced albedo is equivalent to a sudden increase of atmospheric CO2 from 420 to 530 ppm.
The decreased albedo is spurred by reduced atmospheric aerosols and enhanced by feedbacks.
The two major feedbacks expected to darken Earth as the planet warms are reduced sea ice cover and reduced cloud cover. The recent spike of absorbed solar radiation to almost 3 W/m2 may be related in part to the fact that it occurred during the season when solar insolation was rising in the region of Southern Hemisphere sea ice when sea ice cover was at its lowest.
Hansen (2023) Groundhog Day. Another Gobsmackingly Bananas Month. What’s Up?