Clouds remain one of the largest uncertainties in climate science (feedbacks, representation in models, attribution of trends).

Satellite records show declining reflectivity/albedo in recent decades, and dynamical shifts in cloud regimes are documented.

Clouds both cool and warm the Earth

Cooling effect (shortwave / albedo effect)

• Clouds reflect incoming sunlight back to space.
• This reduces the amount of solar energy absorbed by the surface and atmosphere.
• Low, thick, bright clouds (stratus, stratocumulus) are especially effective at this.
• Globally, this cooling effect is strong — without clouds, Earth would be significantly warmer.

Warming effect (longwave / greenhouse effect)

• Clouds absorb infrared (heat) radiation emitted by the Earth’s surface and re-emit some of it back downward.
• This traps heat in the lower atmosphere, similar to greenhouse gases.
• High, thin clouds (cirrus) are particularly effective at this because they are cold and let a lot of sunlight through while still blocking outgoing heat.

Net effect

• On average, clouds have a net cooling effect on the current climate (the shortwave cooling is larger than the longwave warming).
• However, the balance varies strongly by cloud type, altitude, thickness, and location:
  • Low clouds → net cooling
  • High clouds → often net warming
  • Mid-level clouds → more mixed

When the climate warms, clouds themselves change (amount, height, thickness, type).

These changes create cloud feedbacks:

• If low reflective clouds decrease → less cooling → positive feedback (amplifies warming)
• If high clouds rise higher → stronger greenhouse effect → positive feedback
• Other changes can produce negative feedbacks

This is why cloud feedbacks remain the largest source of uncertainty in climate sensitivity estimates (as assessed by the IPCC).

Clouds cool Earth by reflecting sunlight and warm it by trapping heat.

The net result today is cooling, but how that balance shifts in a warmer world is still one of the key open questions in climate science.

CERES satellite data show

Earth’s planetary albedo has declined since 2000, increasing absorbed solar radiation. A large part of this decline is attributed to reductions in the coverage or optical thickness of reflective (especially low) clouds — often described as “cloud contraction” or decreases in high-reflectivity cloud regimes. This is one of the main reasons Earth’s energy imbalance has roughly doubled over the CERES record.

CERES (Clouds and the Earth’s Radiant Energy System) provides the primary continuous satellite record of Earth’s top-of-atmosphere (TOA) radiation budget, including planetary albedo, since March 2000.

CERES instruments (on Terra, Aqua, Suomi-NPP, and NOAA-20) measure:

• Reflected shortwave (solar) radiation
• Outgoing longwave (thermal infrared) radiation

Planetary (TOA) albedo is calculated as:

$$\text{Albedo}=\frac{\text{Reflected shortwave flux (TOA SW up)}}{\text{Incoming solar flux}}$$

The flagship climate data product is CERES Energy Balanced and Filled (EBAF) (currently Edition 4.2 / 4.2.1). It provides monthly global, zonal, and 1°×1° regional means of all-sky and clear-sky fluxes, with the global net TOA flux constrained to match independent estimates of ocean heat uptake. Data extend through at least early 2026 in recent releases.

Official portal: https://ceres.larc.nasa.gov/ (data ordering, visualization tools, quality summaries, and documentation available there).

CERES is widely regarded as the gold-standard observational record for TOA radiation budget trends.

Uncertainties remain in exact attribution of cloud vs. aerosol vs. surface contributions and in the precise magnitude of longer-term trends due to instrument transitions and calibration, but the overall direction (declining albedo → rising ASR and EEI) is robust across editions and independent datasets.

_____________________________________________________________________________________

Earth’s dimming mirror: cloud contraction and the rise of albedo governance

Here is the open-access PDF of the paper:

Published: Environmental Research Letters 21 141002.

DOI: 10.1088/1748-9326/ae8a67

(Received 12 May 2026; revised 6 July 2026; accepted 14 July 2026; published 22 July 2026.)

Authors: Gianni Bellocchi, Vinay Kumar, Fredrik Charpentier Ljungqvist and Nazzareno Diodato

Abstract (slightly cleaned from the PDF extraction)

Earth has reflected progressively less solar radiation since the start of the satellite era (1979), amplifying the planetary energy imbalance. Satellite analyses attribute the trend primarily to circulation-driven contraction of reflective cloud regimes, whereas process-based studies emphasize surface reflectivity changes. We argue that these perspectives are dynamically linked: as cloud cover contracts, diminishing atmospheric masking elevates the realized climatic leverage of surface albedo. This coupling makes surface reflectivity an increasingly important and manageable regulator of solar absorption under clearer-sky conditions. We propose an integrated governance framework that explicitly incorporates albedo management alongside carbon management.

Structure and key points

Growing energy imbalance
CERES data show Earth’s energy imbalance roughly doubled since the early 2000s (≈0.5 → 1.0 W m⁻²). Ocean heat content confirms the acceleration. The authors describe a “clearing-sky” phase (declining aerosols, reduced low-cloud cover, cryosphere reflectivity loss) that lets more shortwave radiation reach the surface, increasing the importance of surface albedo. Regional amplification is noted (e.g., grasslands rising above 1.7 W m⁻²).

Cloud-regime contraction as a leading driver
Citing Tselioudis et al., the paper states that contraction of high-reflectivity cloud regimes accounts for ≈0.37 W m⁻² decade⁻¹, or roughly 80 %, of the observed increase in absorbed solar radiation over 2001–2024. This is linked to large-scale dynamical shifts (narrowing of the ITCZ and poleward shift of mid-latitude storm tracks). Cloud contraction is presented as increasing (not replacing) the radiative influence of the surface by reducing atmospheric

Surface albedo as a strategic, manageable lever
Land-use and management can change surface albedo by 0.05–0.20. The authors discuss practices such as cover cropping, residue retention, and high-albedo urban materials. They note the paradox that biogeophysical (albedo) and biogeochemical (carbon) effects can have opposite signs (e.g., afforestation can darken the surface while sequestering carbon) and therefore call for joint evaluation.

Historical (Mediterranean) context
Multi-centennial cloudiness reconstructions show cloud cover peaking around the coldest phase of the Little Ice Age (~1600 CE) and then declining toward modern minima. The decline began during the later Little Ice Age, preceding strong anthropogenic greenhouse-gas forcing. Suggested contributors include natural variability (post-volcanic recovery, solar activity, AMO) and historical land-use change (European deforestation reducing moisture recycling and convective clouds).

The paper is a perspective, not original observational research.

It synthesizes existing satellite, energy-budget, and paleo/historical evidence and advocates for “albedo governance” as a policy complement to carbon management.