Azara Blog: Solar radiation at surface of Earth increasing

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Date published: 2005/05/06

The BBC says:

The amount of sunlight reaching the Earth's surface is increasing, two new studies in Science magazine suggest.

Using different methods, they find that solar radiation at the surface has risen for at least the last decade.

Previous work had found the opposite trend, leading to a popular theory known as "global dimming".

But the latest Swiss and US research indicates the dimming in the past has now been reversed, possibly because of reduced atmospheric pollution.

The idea of global dimming holds that tiny particles - aerosols - in the atmosphere are reflecting sunlight back into space, and the effect is to cool the Earth's surface.

The aerosols - a large proportion of which come from human activities - are therefore acting against any human-induced greenhouse effect. And only when societies clean up the production of aerosols will the true extent of global warming become apparent.
...
If global dimming was masking the true scale of the human-induced greenhouse effect, and that dimming has now been superseded by global brightening, what does it all mean for the climate?

"We need to understand the basis of this," observed Dr Highwood, "and see what types of aerosol particles might be involved.

"If it's due to changes in soot-type aerosols, which absorb radiation, it might not affect things very much; but if it's changes in particles which scatter sunlight, such as sulphate aerosols, then we might not have the computer models of climate change right.

"But there is a third possibility here, which is changes in cloud cover. Until we can sort this out, we're going to struggle."

Once again, then, a conclusion arrived at by decades of painstaking observation raises a host of further questions, which can only be answered by yet more decades of painstaking observation and the expensive instruments needed to make them.

It's obviously too early to tell what any of this means, but it does illustrate perfectly well how complex this all is (not very surprising, but for political reasons, scientists and so-called environmentalists often pretend it is all black and white).

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