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Nasa carbon space observatory 'watches Earth breathe'

Nasa carbon space observatory 'watches Earth breathe'
From BBC - October 13, 2017

A Nasa satellite has provided remarkable new insights on how CO2 is moved through the Earth's atmosphere.

The Orbiting Carbon Observatory (OCO) tracked the behaviour of the gas in 2015/2016 - a period when the planet experienced a major El Nio event.

This climate phenomenon boosts the amount of CO2 in the air.

The US space agency's OCO satellite was able to show how that increase was controlled by the response of tropical forests to heat and drought.

The forests' ability to draw down carbon dioxide, some of it produced by human activity, was severely curtailed.

The science has significant implications because the kind of conditions associated with El Nios are expected to become much more common under global warming.

"If future climate is more like this recent El Nio, the trouble is the Earth may actually lose some of the carbon removal services we get from these tropical forests, and then CO2 will increase even faster in the atmosphere," explained Scott Denning, an OCO science team member from Colorado State University in Fort Collins. That would amplify warming, he told reporters.

Technical papers describing OCO's work have just been published in Science Magazine.

El Nios occur when warm waters in the western Pacific periodically shift eastwards. This sets off a global perturbation in weather systems, redistributing rainfall and bumping up temperatures.

The 2015/16 event was one of the strongest on record and this was evident in the rise of CO2.

Normally, the concentration of the gas in the atmosphere goes up each year by about two parts per million by volume (ppmv) of air molecules (the current level is just over 400ppmv) - the equivalent of four gigatonnes of extra CO2.

But in this extraordinary period, the jump was 3ppmv, per year - or six gigatonnes.

It is a rate of increase not seen on Earth in at least 2,000 years.

What was remarkable, however, was that human emissions of carbon dioxide were thought to have been relatively static over the same period, meaning something strikingly went wrong with the processes that would normally scrub CO2 from the atmosphere.

OCO's ability to track the gas and sense the rate of photosynthesis in plants provided the answers.

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