“[T]he increase in absorbed solar radiation is primarily due to natural variations in cloudiness and surface albedo, which have served as the main forcing factors of the flux above the atmosphere over the last 2 decades.” – Diodato et al., 2025

It is commonly accepted that there has been a satellite-observed (CERES) cloud cover albedo decline that has led to an increase in solar radiation absorbed by the Earth’s oceans. This increasing trend in absorbed solar radiation (ASR) explains the post-2000 global-scale temperature increase (Dübal and Vahrenholt, 2021, Loeb et al., 2021, Stephens et al., 2022, Koutsoyiannis et al., 2023, Loeb et al., 2024, Nikolov and Zeller, 2024).

And now, in two new studies (Diodato et al., 2024 and Diodato et al., 2025), scientists have begun formulating reconstructions of cloud cover over the Mediterranean region that can be dated all the way back to the Medieval Warm Period, or 970 CE.

The authors suggest their reconstructions of cloud cover may be representative of more than just this region, as it is a product of large scale processes that may “transcend geographical boundaries.” In other words, what happens in the Mediterranean region may well have global implications.

Their reconstructions indicate the modern declining cloud cover trend may not only have been occurring since 2000, but, except for a brief increasing period from about 1945 to 1980 (that coincided with a global cooling trend), it has been ongoing for over 200 years. The “turning point” years were 1815-1818, following the eruption of Mount Tambora. From that point on there has been a precipitous decline in cloud cover that departs from multi-decadal variability.

The authors suggest the “dominant” factors linked to the post-1800s warming trend include solar forcing, volcanic forcing, and the Atlantic Multi-decadal Oscillation (Diodato et al., 2024).

In other words, the modern warming as well as the past climate changes may be “primarily due to natural variations in cloudiness and surface albedo, which have served as the main forcing factors” (Diodato et al., 2025).

Image Source: Diodato et al., 2025

Image Source: Diodato et al., 2024