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Watching carbon dioxide from space

In June, a patch of green develops over Eurasia where carbon dioxide is being stored by plants In June, a patch of green develops over Eurasia where carbon dioxide is being stored by plants NASA OCO-2
05 Nov
2015
Observing the Earth’s atmosphere from space, a NASA satellite illustrates changes in the abundance of carbon dioxide

Carbon dioxide, arguably the world’s most infamous molecule, now has its own constant paparazzi. With the aim of investigating COsources and natural sinks, NASA’s Orbiting Carbon Observatory 2 (OCO-2) satellite has been observing our atmosphere since 2014. Armed with a year’s worth of data, scientists at NASA’s Jet Propulsion Laboratory have put together a time-lapse video that shows dynamic changes in the abundance of CO2, bringing colour to processes that are usually invisible.

CO2 does not remain at a constant level in our atmosphere. As well as being emitted by industry, vehicles and animal respiration, it is also absorbed back into plants and the oceans. Currently, there is an average of 400 parts per million of CO2 in the atmosphere. However, between mid-May and June, the OCO-2 saw a dramatic reduction in the abundance of COacross the northern hemisphere where, due to a process known as the ‘spring drawdown’, plants absorbed CO2 to form new growth.

The visualisation uses red to show the regions that are above, and green the regions below the global average of 400ppm. The spring drawdown can be seen as red turns to green across the northern hemisphere from May to June. The satellite needs clear, cloudless days to record CO2 abundance, for this reason there are many blank days in the northern and southern hemispheres.

The annual springtime drawdown is a major event that NASA expected the satellite to see. Dr Annmarie Eldering, deputy project scientist of the OCO-2, tells Geographical, if you look at that panel over Eurasia around the beginning of June, it’s like someone just took a bite out of things. The spring drawdown decreases the CO2 abundance by as much as two to three per cent, which is a large amount in terms of the global average, If we didn’t see it, we would have known we did something wrong.’

Eldering also expected an increase in CO2 abundance near human activity, with higher percentages near regions where fossil fuels are consumed by mega cities and power plants. Higher percentages over African countries were also expected: ‘There is a lot of biomass burning in African countries as part of clearing fields for agriculture. The satellite allows you to plainly see this process with your eyes.’

With 2016 looking to become an El Nino climate event, the Jet Propulsion Laboratory will be investigating how this can impact CO2. ‘The El Nino is likely to make sea temperatures much warmer,’ says Eldering. ‘This could decrease how much COis dissolved in the ocean.’ She says that the satellite is beginning to show this link. NASA will also be looking at the peat fires in Indonesia, which are thought to be throwing large amounts of carbon dioxide into the atmosphere. ‘Now, I hope, we will have more details about the Indonesian fires in terms of overall CO2 abundance.’

The tricky part is how small these changes compare to the average abundance of CO2. Even the biggest events, such as the springtime drawdown, only change the amount by a couple of per cent. ‘Meanwhile, the events we still care about such as Indonesian fires and El Nino change it by only half a per cent or even less,’ says Eldering, ‘so you want to be able to observe when CO2 changes by that small proportion.’

Eldering says the OCO-2 has managed to catch these small changes: ‘The good news is we think we have succeeded. We believe our satellite can now make measurements of CO2 to better than a quarter of a per cent.’

The OCO-2 has one year left to orbit. However, Eldering says if the instrument continues to perform well, there is a process within NASA to apply to extend its mission.

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