A recent UCLA- led study finds that Earth’s atmosphere has become about 10% less dusty from 2003 to 2023, which may have modestly contributed to recent global warming because atmospheric mineral dust has a slight net cooling effect.
The research (published in Science Advances) combined data from multiple satellites (lidar, infrared sounders, and multi-spectral imagers), three atmospheric aerosol reanalyses/databases, and ground-based AERONET stations. It provides the strongest evidence yet of a coherent global decline in the dust cycle, including dust aerosol optical depth (DAOD), loading, emissions, and deposition. North Africa (the dominant source) and Asia each showed roughly 10% declines, driving the global trend.
Dust primarily cools the planet by reflecting sunlight (shortwave effects), though it also has complex interactions with longwave radiation, clouds, and precipitation. The observed decline produced a small positive effective radiative forcing of about +0.02 ± 0.05 W m⁻² over 2003- 2023, meaning a modest loss of cooling that may have slightly amplified human- caused warming.
Additional effects include:
- Air quality: Lower dust is beneficial for respiratory health for hundreds of millions of people in dust-prone regions (e.g., Sahel, Middle East, northern China).
- Ecosystems: Reduced transport of nutrients such as iron and phosphorus that fertilize oceans and land.
- Other: Influences on clouds, rainfall (including monsoons), and the reflectivity of snow/ice.
Dust levels remain higher than pre- industrial times (they rose through much of the 20th century and peaked around the 1980s). Some current dust still comes from human- influenced sources such as drying lakebeds.
Preliminary analysis points mainly to weaker surface winds (dust emission is highly sensitive to wind speed) and increased vegetation cover (“greening”), particularly over Asia and China. Researchers (including lead author Ashok Gupta, now at Vanderbilt, and co-author Jasper Kok at UCLA) are investigating the drivers further, including implications for future climates.
Atmospheric mineral (desert) dust has a modest net cooling effect on Earth’s climate overall, though the exact magnitude remains uncertain and includes both cooling and warming components.
Dust interacts with radiation in two main ways:
- Shortwave (solar) radiation – primarily cooling
Dust particles scatter (reflect) incoming sunlight back to space. This reduces the energy reaching Earth’s surface and atmosphere.- Central estimate of the shortwave direct radiative effect (DRE): about −0.40 W m⁻² (range roughly −0.10 to −0.70 W m⁻²).
- Finer particles are more efficient scatterers; coarser particles absorb more solar radiation.
- Longwave (thermal infrared) radiation – primarily warming
Dust absorbs and scatters outgoing heat radiation from Earth, acting somewhat like a greenhouse gas and trapping heat.- Recent observationally constrained estimates put the longwave DRE at about +0.25 ± 0.06 W m⁻² (nearly twice what most climate models simulate, partly because models under-represent super-coarse dust >10 μm and omit longwave scattering).
Net direct radiative effect (shortwave and longwave) is typically estimated around −0.15 ± 0.35 W m⁻².
When including additional pathways, effects on clouds, atmospheric chemistry, snow/ice albedo (dust darkens snow and reduces reflectivity), and biogeochemistry, the overall dust effective radiative effect is assessed as:
- −0.2 ± 0.5 W m⁻² (90% confidence interval)
This indicates that dust is more likely to cool the climate than to warm it, but the uncertainty range still allows for a small net warming or near-zero effect.
Recent studies incorporating better mineralogy data (e.g., from NASA’s EMIT mission) and size distributions sometimes find weaker net cooling (near-neutral or around −0.06 W m⁻² in some model setups) or stronger cooling (e.g., −0.68 W m⁻² when using regionally varying refractive indices). The sign and magnitude remain an active research area.
Historical and recent changes
- Global dust mass loading increased by about 55 ± 30% since pre-industrial times (mainly from Asia and North Africa). This produced an effective radiative forcing of roughly −0.07 ± 0.18 W m⁻², modestly counteracting greenhouse- gas warming.
- From 2003- 2023, atmospheric dust declined by ~10%. Because dust cools overall, this reduction produced a small positive forcing of +0.02 ± 0.05 W m⁻², meaning a modest loss of cooling that may have slightly contributed to recent rapid warming.
Regional variations
- Over dark surfaces (oceans): stronger cooling (scattering dominates).
- Over bright surfaces (deserts, snow/ice): weaker cooling or local warming (absorption becomes more important; deposited dust further reduces surface albedo).
- Near major sources (e.g., Sahara): strong surface cooling but atmospheric heating.
In short: Dust’s dominant cooling comes from reflecting sunlight, partially offset by its heat- trapping longwave effects and other interactions. The best current assessment is a small net global cooling, but large uncertainties mean better constraints on particle size, mineral composition (especially iron oxides), and cloud interactions are still needed. This is why the recent observed decline in dust is viewed as removing a small cooling influence.
A global decline in atmospheric dust during the 21st century
This is the full scientific paper corresponding to the Phys.org/UCLA news coverage:
“A global decline in atmospheric dust during the 21st century”
Key findings (from the abstract and results)
Researchers reconstructed the global dust cycle for 2003- 2023 using a large- ensemble inverse modeling framework that integrates:
- Multiple satellite DAOD (dust aerosol optical depth) products (lidar, infrared sounders, multi- spectral imagers, including LIVAS/CALIPSO, MIDAS, IASI-LMD)
- Three aerosol reanalyses (MERRA-2, CAMS, NAAPS)
- Ground-based AERONET observations at dust- dominated sites
Main results:
- Global atmospheric dust declined by −10 ± 8% between 2003 and 2023 (roughly −5 ± 4% per decade).
- North Africa (still the dominant source) declined by −10 ± 8%.
- Asia declined by −10 ± 12%.
- Parallel declines occurred in dust loading, emissions, and deposition, indicating a coherent weakening of the entire global dust cycle.
- Individual satellite products largely agree on the downward trend (the strongest evidence to date that the planet became less dusty in the early 21st century).
Climate impact:
The decline produced a positive effective radiative forcing of +0.02 ± 0.05 W m⁻² over 2003–2023. Because dust has a net cooling effect overall, its reduction removes some of that cooling and may have modestly contributed to the rapid warming and growing Earth’s energy imbalance of the past two decades.
Additional context from the paper
- All seven major DAOD products show negative global trends over the overlapping 2008- 2021 period, though magnitudes vary.
- Trends are strongest over major source regions; some outflow regions (e.g., parts of the tropical North Atlantic) show more mixed or locally positive signals, possibly linked to transport and wet-scavenging changes.
- AERONET evaluation shows IASI-LMD and MERRA-2 best match observed long-term trends at dust-dominated sites.
- The reconstruction produces ready- to- use global datasets of emissions, loading, deposition, and DAOD for use in climate models.
The paper notes that the causes of the decline (weaker surface winds, vegetation “greening,” etc.) are still under investigation, and that dust levels remain elevated relative to pre-industrial conditions.
This matches the news summaries: less dust is good for air quality in exposed regions but removes a small cooling effect and reduces nutrient deposition to ecosystems.
Published: Science Advances (2026)
Provided: University of California, Los Angeles
Authors: Ashok K. Gupta, Jasper F. Kok, and colleagues
Abstract
Mineral dust affects Earth’s energy budget, clouds, and biochemistry, yet the evolution of the global dust cycle in recent decades remains shrouded in uncertainty. Here we reconstruct the global dust cycle during the early 21st century by integrating a suite of global dust aerosol optical depth (DAOD) products from satellite-borne lidar, infrared sounders, and multispectral imagers; three aerosol reanalyses; and a compilation of dust-dominated AERONET sites into a large-ensemble inverse modeling framework. We show that North Africa has remained the dominant global dust source, yet it has experienced a decline in DAOD of −10 ± 8% between 2003 and 2023. A comparable reduction is observed across Asia (−10 ± 12%), together driving a global decrease of −10 ± 8%. Similar declines in dust loading, emissions, and deposition indicate a coherent reduction of the global dust cycle. Individual satellite products converge on overall similar trends, providing the strongest evidence to date that the planet has become less dusty in the early 21st century. This decline in atmospheric dust has exerted a positive effective radiative forcing of +0.02 ± 0.05 watts per square meter over 2003–2023, implying that declining atmospheric dust might have modestly contributed to the rapid warming of the past two decades.
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