I know I have commented on horticulturists pumping CO2 into greenhouses to increase plant growth before.
I just can't figure out which threat - I have searched.
...anyway this is a little more comformation the plants have a role in all this that will surprise some.Carbon dioxide intake soars PALOMA MIGONE
Last updated 06:42 12/07/2012
Scientists have discovered that plants, trees and soil have abruptly increased their atmospheric carbon dioxide intake in the last 20 years.
The land biosphere was taking in about one billion tonnes of carbon per year since 1988, equal to about 10 per cent of the global fossil fuel emissions for 2010.
However, the sudden shift didn't mean people shouldn't worry about climate change in the future, Niwa atmospheric scientist Dr Sara Mikaloff-Fletcher said.
Without nature's new uptake regime, the amount of carbon in the atmosphere would probably have increased even more rapidly over the last two decades.
And if the change was temporary, reducing C02 levels in the future might get harder.
''At the end of the day there may have been this natural sink which has tremendously been to our advantage, but that has not stopped CO2 from increasing in the atmosphere,'' Dr Mikaloff-Fletcher said.
''It's not enough. CO2 is still increasing in the atmosphere at an alarming rate.''
The discovery was reported in the journal Global Biogeochemical Cycles, written by an international team of scientists including Dr Mikaloff-Fletcher.
She said while the study showed there was a natural shift, scientists didn't know how it would change in the future.
''We don't yet know whether or not the natural process is going to cause a permanent shift towards this increase uptake or if that's something that could be reversed or something that can be enhanced.
''That's going to be the subject of the next series of studies on this topic.''
Scientists explored whether the increase could be explained by the EL Nino Southern Oscillation (Enso) - and it couldn't.
''We also tried volcanic activity. A little bit after the shift happened, in 1991, there was a big eruption, but the problem was that the shift happened too early,'' Dr Mikaloff-Fletcher said.
Kevin Tate, research associate at Landcare Research, said he was ''intrigued'' by the findings.
''One thought struck me and that is that perhaps to this point we have underestimated the size of the terrestrial sink, and this work may be correcting that.''
He believed a number of factors could have contributed to the increase, such as CO2 fertilisation, and afforestation and reforestation.
Some sources like deforestation and permafrost melting may have been overestimated previously as well.
''While this result is intriguing, it must be remembered that terrestrial sinks are finite, and there is a strong likelihood that the terrestrial sink will become increasingly saturated in coming decades.''
Researchers already knew that over half of the emissions of C02 from human activities were absorbed by the land biosphere and the oceans. But Dr Mikaloff-Fletcher said the ''natural sinks'' were difficult to quantify directly.
Using data from 1958 and mathematical techniques that haven't been widely used in the field, scientists took the amount of emissions and subtracted what was retained in the atmosphere and what the oceans took up, leaving the land component for the study.
They noticed the abrupt shift in 1988, when the intake of 0.3 billion tonnes of carbon per year surged to one billion tonnes.
The amount of CO2 in the atmosphere was calculated from a global network of stations, including Niwa's sites in New Zealand and Antarctica.
http://www.stuff.co.nz/science/7265266/Carbon-dioxide-intake-soars
