Brighter Days Behind Us
It turns out that one of the paradoxical effects of human-directed climate change is that even as the earth’s average temperature increases, the intensity of direct sunlight hitting the surface is decreasing due to the scattering effects of aerosolized pollution and dust high in the atmosphere. So when some old person tells you that it was brighter and sunnier and generally less cloudy when they were a kid they are probably right. This effect is most pronounced in the temperate zones and has implications for the solar energy industry, agricultural crop growing, and will even begin to affect the earth’s average albedo (due to reduced dark plant growth in the northern tunda zones).
It’s interesting to note that Earth’s closest twin planet in terms of position and size is Venus, where a runaway Greenhouse Effect keeps surface temperatures around Venusian a toasty 480?C (894?F) but the entire planet is mired in a perpetual twilight gloom (verified by the Russian landers) due to the extraordinarily thick atmosphere (around 9000 kPa or around 90 times Earth’s atmospheric pressure). Venus’s oceans long ago boiled away in this runaway Greenhouse Effect. The oceanographic runaway Greenhouse Effect begins to occur over large bodies of water at around 27?C (80?F). Even ignoring current human-directed climate change, the increasing solar output of the Sun as it moves along a typical Main Sequence stellar evolutionary path means that sooner or later the Earth’s oceans will also vaporise and temperatures soar quickly to Venusian levels. Strange days indeed lie ahead of us…
Ohmura’s results suggested that levels of solar radiation striking the Earth’s surface had declined by more than 10% in three decades … Records show that over the past 50 years the average amount of sunlight reaching the ground has gone down by almost 3% a decade … levels of solar radiation reaching parts of the former Soviet Union had gone down almost 20% between 1960 and 1987 … “The cloudy times are getting darker,” says Cohen, at the Volcani Centre. “If it’s cloudy then it’s darker, but when it’s sunny things haven’t changed much.” … “If the greenhouse effect causes global dimming then that really changes the perspective,” he says. In other words, while it keeps getting warmer it might keep getting darker.
Earlier here.