Warnings Over... Clean Air!

[manxiememe]

http://news.aol.co.uk/environment-news/war...rsp=uk_environm

 

Warning about impact of cleaner air

 

Efforts to lower air pollution levels could lead to plants absorbing carbon dioxide less efficiently - making tackling climate change more difficult, scientists have warned.

Researchers found that plants have been taking in CO2 at a higher rate under skies made hazy by pollutants in past decades than they would if the atmosphere was cleaner.

The "global dimming" phenomenon caused by an increase in microscopic particles, such as sulphates, as a result of human activity reduced the amount of sunlight reaching the Earth's surface from the 1950s to 1980s.

But while less sunlight reduces photosynthesis - the process in which plants absorb carbon - atmospheric particles scatter light so that the surface of the land receives light from different directions rather than just directly from the sun.

 

As a result, plants are able to convert more of the sunlight energy into growth, trapping carbon dioxide as they do so, because fewer leaves are in the shade.

While some of the particles known as aerosols are natural phenomena including volcanic ash, desert dust and sea salt, much is caused by human activity such as burning wood or fossil fuels for power or petrol in cars.

Efforts to cut carbon emissions will therefore reduce aerosols in the atmosphere - and at a faster rate than CO2 levels take to stabilise.

The aerosols also need to be reduced because of their negative impact on human health but the researchers, writing in the journal Nature, warned that because of the effect of pollution on carbon storage, steeper cuts in fossil fuel emissions would be needed to stabilise the climate if aerosol levels fell as expected.

The study's lead author Dr Lina Mercado from the Centre for Ecology and Hydrology said: "Surprisingly, the effects of atmospheric pollution seem to have enhanced global plant productivity by as much as a quarter from 1960 to 1999. This resulted in a net 10% increase in the amount of carbon stored by the land once other effects were taken into account."

The researchers from the Centre for Ecology and Hydrology, the Met Office Hadley Centre, ETH Zurich and the University of Exeter looked at how the impact of aerosols on the absorption of CO2 by plants would affect attempts to fight climate change. Under environmentally-friendly scenarios in which sulphate aerosols decline rapidly in the 21st century, steeper cuts in greenhouse gases will be needed to compensate for lower plant productivity carbon storage, they said.