Australian news, and some related international items

Rising soil temperatures cause release of carbon, increasing climate change

Warming soils release carbon to further accelerate climate change, Independent Australia  Climate News Network 26-year study find rising temperatures could cause soils to release carbon on a scale with the potential to accelerate climate change even further. Tim Radford reports.

As the world’s soils warm, they may surrender potentially dangerous amounts of carbon to the atmosphere. Rising temperatures could mean rising levels of carbon dioxide respired by the microbes underfoot.

The world’s longest-running soil-warming experiments deliver no easy assurances forests will continue to absorb atmospheric carbon that pours from vehicle exhausts, power stations and factory chimneys as humans burn fossil fuels, raise greenhouse gas levels and send the planetary thermometer ever higher.

The conclusion is based on a set of experiments described in the journal, Science.

Carbon budget

Since 1991, researchers have been measuring the soil carbon traffic in Harvard Forest, Massachusetts, in the United States. In this forest are sets of plots six metres square. Some are left wild. Some have electric cables dug into the soil to deliver 5°C warmth of the kind that might be expected later this century. Some have soil disturbed but not warmed. Researchers tried every combination and compared the soil carbon loss over time.

They measured phases of substantial carbon loss from the warmed soils, alternating with phases of no detectable loss. That is: they measured soil carbon loss to the atmosphere, and stasis, but never observed evidence that warmed soils might store carbon more efficiently. Altogether, the warmed soils lost 17% more of the carbon stored in the top 60 centimetres than unheated soils.

“We know that microbial soil respiration is a major, and natural, source of greenhouse gases to the atmosphere. Using the long-term warming experiment as a window into future climate change, we see that warming has a profound but discontinuous effect on greenhouse gas emissions,” says one of the authors, Kristen DeAngelis, assistant professor of microbiology at the University of Massachusetts at Amherst.

The carbon budget – the flow of carbon into and from the atmosphere – is at the heart of all climate change forecasting. …….,10837


October 19, 2017 - Posted by | General News

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