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As greenhouse gas emissions rise, carbon fingerprint points to fossil fuels - 26/11/2019

Greenhouse gas emissions are continuing to rise, and combustion of fossil fuels is the only explanation for the changing makeup of atmospheric CO2, according to the latest figures released by the World Meteorological Organization (WMO).

The WMO’s Greenhouse Gas Bulletin is released once a year, and GNS Science’s Jocelyn Turnbull is one of the lead authors.

The Bulletin found concentrations of carbon dioxide (CO2) increased at about the average rate over the past 10 years, reaching 407.8 parts per million – while methane (CH4) and nitrous oxide (N2O) rose faster than average.

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Not all greenhouse gases are created equal, and measuring the isotopic content gives us a ‘fingerprint’ of where and how that gas was emitted

Dr Jocelyn Turnbull

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The Bulletin identifies a rise in CO2 concentration – but a decline in the relative amounts of the two heavy carbon isotopes. Carbon-14, or radiocarbon, is entirely absent in fossil fuels, and carbon-13 is present in lower amounts in fossil fuels than in the atmosphere.

These results tell us that the rise in CO2 emissions can only be explained by ongoing release of CO2 by burning fossil fuels.

Meanwhile, close analysis of atmospheric methane suggests biogenic emissions – such as those from wetlands, ruminant animals or waste – are the main reason for recent increases.

“Not all greenhouse gases are created equal, and measuring the isotopic content gives us a ‘fingerprint’ of where and how that gas was emitted,” Dr Turnbull says.

“The studies included in the Bulletin indicate clearly that human behaviour – in driving vehicles, burning fossil fuels and farming – are the main reason greenhouse gas concentrations are rising.”

Dr Turnbull is part of the NIWA-led CarbonWatch-NZ project, working with Maanaki Whenua Landcare Research, the University of Waikato and Auckland Council to build a complete top-down picture of New Zealand’s carbon balance.

CarbonWatch-NZ is funded through the MBIE Endeavour Fund.

“GNS Science’s work as part of CarbonWatch-NZ will help us to determine how our emissions are tracking, and what policies are having an effect,” Dr Turnbull says.

“Our work, along with all the other research being conducted in the climate space, will help policy-makers take a more evidence-based approach to these massive challenges.”

Click here to download a PDF of the WMO report

Jocelyn Turnbull