Global dimming and brightening

When less sunlight reached the ground

The dip in the radiation curve in the sixties and seventies connects to a wider climate story. What does the local series show — and what can it not prove?

Solar radiation around Kanjiža

1951–2025 · kWh/m²/day

Annual mean10-year moving averageMinimum within 1960–1989

Minimum within 1960–1989: 1972 · 3.32 kWh/m²/day
Latest complete year: 2025 · 3.82 kWh/m²/day

The local model shows a change, but cannot establish its cause on its own.

The Sun did not become weaker

Energy reaching the ground also depends on clouds, airborne particles and atmospheric conditions. This curve describes surface radiation, not a change in the Sun’s own output.

Dimming, then brightening

Surface observations in many regions show declining sunlight from roughly the 1950s to the 1980s, known as global dimming. Partial brightening followed in many places. European studies document similar changes, but their timing and magnitude vary by location.

What can drive these changes?

Aerosols, including particles from industrial emissions, scatter or absorb light and affect clouds. Reduced emissions may have contributed to later brightening. Clouds and atmospheric variability also matter; a single local radiation curve cannot separate their contributions.

Were nuclear tests responsible?

Probably not as the main cause. Most atmospheric nuclear tests ended with the 1963 Partial Test Ban Treaty, and stratospheric particles settle within a few years. Dimming, however, lasted for decades, pointing to a continuous source such as sulphur emissions from coal and oil combustion.

The clean-air paradox

Burning fossil fuels releases both warming carbon dioxide and cooling sulphate aerosols. Aerosols partly masked warming; James Hansen called this a “Faustian bargain”. Rules against acid rain and smog brought cleaner air, a clear gain for health and ecosystems, but as the masking weakened, CO₂ warming became more visible. The lesson is not to keep polluting, but to cut greenhouse gas emissions.

A modern parallel: sulphur in ship fuel

From 2020 the International Maritime Organization (IMO) sharply limited sulphur in ship fuel. Clouds over shipping lanes became less bright, and studies suggest this may have contributed modestly to record ocean surface warmth in 2023–2024. It is a small-scale replay of what happened over land from the 1980s.

What does the Kanjiža curve tell us?

This is a model-based ERA5-Land reanalysis, not decades of direct observations at a Kanjiža station. The dip and later changes appear in the series, but alone cannot prove that aerosols caused them here. Independent measurements and a dedicated attribution study are needed.

What does this mean for solar panels?

With identical system settings, more incoming radiation generally means more modeled production. Actual yields also depend on orientation, temperature, shading and losses. We therefore do not claim a universal local 10–15% production increase for every system.

Data and method

Copernicus C3S / ERA5-Land SSRD point time series; grid cell: 46.1°N, 20.1°E. Mean daily radiation reaching a horizontal surface in kWh/m²/day (MJ ÷ 3.6), weighted by observed days. Only calendar years with full daily coverage are included; current and incomplete years are excluded. The moving average uses the current and previous nine complete consecutive years. Contains modified Copernicus Climate Change Service information.