Today a group of German scientists presented data suggesting Earth is absorbing more sunlight than in the past, reports Ars Technica, “largely due to reduced cloud cover.”
We can measure both the amount of energy the Earth receives from the Sun and how much energy it radiates back into space…. The new paper finds that the energy imbalance set a new high in 2023, with a record amount of energy being absorbed by the ocean/atmosphere system. This wasn’t accompanied by a drop in infrared emissions from the Earth, suggesting it wasn’t due to greenhouse gases, which trap heat by absorbing this radiation. Instead, it seems to be due to decreased reflection of incoming sunlight by the Earth….
Using two different data sets, the teams identify the areas most effected by this, and they’re not at the poles, indicating loss of snow and ice are unlikely to be the cause. Instead, the key contributor appears to be the loss of low-level clouds [particularly over the Atlantic ocean]… The drop in low-level clouds had been averaging about 1.3 percent per decade. 2023 saw a slightly larger drop occur in just one year….
So, what could be causing the clouds to go away? The researchers list three potential factors. One is simply the variability of the climate system, meaning 2023 might have just been an extremely unusual year, and things will revert to trends in the ensuing years. The second is the impact of aerosols, which both we and natural processes emit in copious quantities. These can help seed clouds, so a reduction of aerosols (driven by things like pollution control measures) could potentially account for this effect. The most concerning potential explanation, however, is that there may be a feedback relationship between rising temperatures and low-level clouds. Meaning that, as the Earth warms, the clouds become sparse, enhancing the warming further. That would be bad news for our future climate, because it suggests that the lower range of warming estimates would have to be adjusted upward to account for it.
If the decline in reflectivity wasn’t just caused by normal variability, the researchers warn, “the 2023 extra heat may be here to stay…”
