For some of us the future really is bright. Researchers have been tracking changes in the apparent brightness of the sun for decades. Globally there was a gradual dimming from the 1940s to the 1980s, but since then the sunlight has been increasing in some areas.
This “solar brightening” effect has been noted in Europe and north America, while other areas, including China and India, have continued to experience dimming.
Natural variations in cloud cover may be partly responsible, but the effects are likely to be related to airborne pollutants, especially particulates. These reflect sunlight, and can influence the formation of clouds.
The timing of the brightening in the US and Europe corresponds to new clean-air laws, while particulates have increased in China and India as dimming has intensified.
The effect is relatively small, less than one per cent of total sunlight. But it may influence plant growth, as growing things are sensitive to available sunlight.
In a paper, published in Nature, crop researchers estimate that solar brightening has been responsible for 27% of the increase in US corn production over the last 30 years. It had been assumed that all the improvement was down to better fertiliser, pesticide and grain.
The continuing brightening is good news for farmers in the areas where it is happening. However, the findings also mean that earlier models used to predict crop yields were inaccurate. Our food supply may depend, more than anyone realised, on subtle environmental factors.
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