The Sun Didn’t Change—We Did: How Humans Dimmed and Brightened the Earth

When pollution rises, sunlight fades

ZURICH — Sunshine is making a surprising return in some parts of the world after decades of growing dimmer. International scientists tracking the amount of sunlight reaching the Earth’s surface have discovered major shifts in solar radiation patterns that directly impact everything from crop yields to solar energy production.

For years, you might have noticed the sun didn’t seem as bright as it once did. This wasn’t just your imagination. From roughly the 1950s to the 1990s, many regions worldwide experienced what scientists call “global dimming,” a measurable decrease in surface solar radiation. But in recent decades, something unexpected has happened: the sun has begun shining brighter again in several regions, particularly in places that have cracked down on air pollution.

Dimming and Brightening Patterns Worldwide

A new perspective paper published in the journal Advances in Atmospheric Sciences reveals how this solar roller coaster ride affects our daily lives, from warming temperatures to food production, with a special focus on dramatic changes observed in China.

The authors, led by Martin Wild from the Institute for Atmospheric and Climate Science at ETH Zurich, note that China has experienced particularly significant variations. Substantial solar radiation decline from the 1960s through the 1990s was followed by signs of reversal in the 2000s and a slight recovery in recent years.

This global dimming and brightening phenomenon isn’t uniform across the planet. The paper shows that while Europe, Japan, and the United States experienced dimming until the 1980s followed by brightening thereafter, China only began showing recovery after 2000. Meanwhile, India continues to see declining sunlight levels throughout the entire study period.

What’s causing these dramatic shifts in sunshine? The primary suspect is air pollution. Aerosols, tiny particles suspended in the air from industrial emissions, vehicle exhaust, and other pollution sources, scatter and absorb sunlight before it reaches the ground. As pollution increased during industrialization, less sunlight reached the Earth’s surface. When regions implemented air quality regulations, the skies began to clear, and solar radiation increased.

When researchers compared Chinese ground-based measurements with satellite data that didn’t account for aerosol changes, they found a revealing mismatch. While actual measurements showed dimming until 2007 and brightening thereafter, satellite data that only considered cloud variations showed the opposite pattern, brightening until 2007 and dimming afterward. This discrepancy reveals the significant influence of increasing aerosol pollution before 2008 and decreasing pollution afterward, effects that weren’t captured in satellite observations.

Effects of Changing Sunlight

These changes in sunlight impact our daily lives in profound ways. In China, researchers have calculated that dimming reduced greenhouse gas-induced warming by 0.139°C per decade for land surface temperatures between 1960 and 2003. This helps explain why daily maximum temperatures increased less than minimum temperatures in China during this period: daytime heat was partially masked by reduced sunlight.

The paper also explains how dimming affects evapotranspiration (the process by which water transfers from land to the atmosphere through evaporation and plant transpiration), agricultural yields, and even underwater ecosystems. One study estimated that sunshine reduction explained 87% of decreased potential maize yield in the North China Plain. Another found that solar dimming contributed to underwater darkening in Chinese lakes, harming aquatic plant growth and fisheries.

The Billion-Dollar Question

For the rapidly expanding solar energy sector, these changes represent billions of dollars in potential revenue. The researchers cite studies showing that if sunlight levels in China could fully recover from decades of dimming to the cleaner conditions of the 1960s, Chinese photovoltaic power production, or the amount of solar energy China produces, could increase 12-13%. That translates to an economic benefit of approximately $6 billion annually based on projected 2030 solar infrastructure.

As countries implement air quality regulations and transition to clean energy, brightening trends may accelerate in currently polluted regions. However, the researchers caution that other factors, including natural climate variations and cloud patterns, can also influence radiation patterns in complex ways.

The sunlight reaching our planet isn’t constant; it responds to our pollution patterns and climate choices. If we want to power the future and protect the planet, we need to start with the skies—because shifts in sunlight affect everything from crops to climate resilience.