Focus on warming, not emissions, say researchers

Focus on warming, not emissions, say greenhouse gas researchers

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CLIMATE IMPACT: Currently used climate metrics can not give the full picture of how agricultural greenhouse gas emissions contribute to global warming, according to new research.

CLIMATE IMPACT: Currently used climate metrics can not give the full picture of how agricultural greenhouse gas emissions contribute to global warming, according to new research.

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Taking account of the warming effect of different greenhouse gases - not their carbon emissions - would change the way methane was treated in emissions reductions targets.

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Taking account of the warming effect of different greenhouse gases - not their carbon emissions - would change the way methane was treated in emissions reductions targets.

New research released earlier this month says current greenhouse gas accounting was inaccurate because it failed to distinguish between short-lived gases, such as methane, and long-lived gases, such as carbon dioxide.

Climate researchers at the University of Oxford said a new metric that demonstrated how different greenhouse gases warmed the earth's atmosphere over time would enable countries to create accurate emissions budgets.

This would allow them to meet the Paris Agreement goal of keeping global warming below 2 degrees Celsius.

One of the paper's co-authors is Dr John Lynch, who is with the Livestock, Environment and People (LEAP) project, part of the Oxford Martin Programme on the Future of Food.

He said currently used climate metrics could not give the full picture of how agricultural greenhouse gas emissions contributed to global warming or the impacts of changing what we eat or how we farm.

"Our new means of reporting warming-equivalent emissions provides a more reliable way of linking emissions and global temperature," he said.

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In a study published in the journal NPJ Climate and Atmospheric Sciences, the researchers recommended a "CO2-warming-equivalence (CO2-we)" metric replace the current "CO2-equivalence (CO2-e)", .

"The headline goal of the Paris Agreement is to keep global warming well below 2°C, and to strive to stay below 1.5°C," Dr Michelle Cain, of the Oxford Martin Programme on Climate Pollutants, who led the study said.

"These are clear temperature-based targets.

"It therefore makes sense to set emissions reductions targets based on how much warming they will cause or avoid.

"We can do this using CO2-warming-equivalence."

Currently, emissions of greenhouse gases other than carbon dioxide (CO2) are measured by their CO2-equivalence.

But the researchers said this was a false equivalence for greenhouse gases that did not accumulate in the atmosphere over time in the way that CO2 did, and had led to an incorrect assumption that all emissions must reach net zero to reach the Paris goals.

Methane, for example, is a more powerful greenhouse gas per kilogram than CO2, but only about half of 2009's methane emissions remain in the atmosphere today and continue to contribute warming, they said.

In contrast, almost all the CO2 from that year remained - and would remain and continue to cause warming for a century or more.

The proposed metric links greenhouse gas emissions with their warming outcomes, no matter their lifespan.

This means the warming impact of all greenhouse gases can be calculated directly from reported emissions, allowing short-lived gases like methane to be effectively budgeted.

Countries' contributions under the Paris Agreement could also be assessed against the Paris goals easily and transparently using this metric, both individually and collectively.

"Setting targets in terms of temperature - not emissions - is what is so important, because we can get to net-zero warming without net-zero emissions of every greenhouse gas," Dr Cain said.

"Short-lived gases decay quickly, so as long as emissions are declining, warming from those sources is declining too.

"On the other hand, because CO2 lasts for centuries, even millennia, every tonne continues to add to warming, even as emissions decline.

"Understanding this we can see more clearly where we need to target efforts to mitigate climate change.

"Reducing methane emissions provides an immediate, but short-term, benefit.

"Whereas to truly tackle the long-term damage we are doing to the climate, the focus needs to be on CO2 and other long-lived pollutants.

"Widespread use of this metric to set targets could ultimately be a game-changer in keeping keep global warming well below 2°C."

This method builds on previous work and is based on the direct relationship between methane emissions and the warming those emissions generate.

This story first appeared on Australian Dairyfarmer

The story Focus on warming, not emissions, say researchers first appeared on Farm Online.

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