(Photo by Ricky Esquivel via Pexels)
By Stephen Beech
Air pollution has a "dramatic" impact on the amount of sunlight reaching Earth’s surface, reveals new research.
Solar radiative energy declined in large parts of the world from the 1950s to the 1980s - known as "global dimming" - before a partial recovery since, say scientists.
The findings of an international research team, published in the journal Advances in Atmospheric Science, suggest that stages of “dimming” and “brightening” correspond with increased air pollution and implementation of clean energy solutions, respectively.
Study corresponding author Professor Martin Wild, of the Swiss Federal Institute of Technology (ETH Zürich), said: “The amount of sunlight - which is solar radiative energy - we receive at the Earth’s surface is not necessarily stable over the years but can undergo substantial decadal variations, as documented in the long-term historical solar radiation measurements we examined.
“These indicate declining solar radiative energy in large parts of the world from the 1950s to the 1980s - known as global dimming - and a partial recovery thereafter, known as brightening, at many observation sites.”
(Photo by Gije Ch
After reviewing existing scientific literature on dimming and brightening research, which dates to the early 20th Century and spans the globe, the team focused on regional trends of solar radiative energy in China.
Wild said: “China provides a conducive environment for understanding aerosol radiative effects - or how air pollutants impact the amount of solar radiative energy reaching Earth’s surface.
“China has well-organized, long-term and spatially uniform surface observations, making the country one of the most intensively studied world regions in terms of dimming and brightening, as reflected in an impressive number of related publications.”
Previous studies found that variations in solar energy reaching the Earth’s surface were particularly pronounced in China.
Solar energy substantially declined from the 1960s to the 1990s, and the trend appeared to begin to reverse in the 2000s with a slight recovery in more recent years.
Wild said: “The causes for these dramatic changes are thought to be primarily due to increasing air pollution in the ‘dimming’ phase, and due to the successful implementation of air pollution mitigation measures in the ‘brightening’ phase."
He explained that air pollution from increasingly used fossil fuels and carbon emissions over the years can literally intercept incoming solar radiation and prevent it from reaching the Earth's surface.
(Photo by Rayhan Ahmed via Pexels)
The more pollution in the atmosphere, the less sunlight reaches Earth’s surface.
Wild says now that China has started to reverse the trend by reducing air pollution, more sunlight is researching the surface, which could have compounding benefits.
He said: “If China fully recovers from the dimming phase and reverts to the clean atmosphere levels of the 1960s, the country could make substantial gains in solar power production.
“These decadal changes of dimming and brightening in the available solar energy are not only crucial for various aspects of climate and environmental change but are also of significant importance for resource assessments in the rapidly growing sector of solar power production."
Wild added: "The availability of solar energy at the Earth’s surface is such a critical factor for so many relevant ecological and societal aspects, as well as for the existence of life in the first place, that it deserves a sustained investment into its investigations as well as its long-term monitoring both from the surface and space.”
But the research team warned that there are "challenges" in fully understanding the dimming and brightening phenomenon’s magnitude, causes and implications.
They recommend that researchers in the field work together and focus on optimally combining the diverse information contained in their different but complementary sources of data.
