By Carlyn Kranking and Grace Rodgers, Nov. 19, 2020 –
At the first 2020 Presidential debate, President Donald Trump said that Green New Deal supporters “want to take out the cows” to reduce greenhouse gas emissions.
Not only is this claim untrue, but eliminating cows, which notoriously produce the greenhouse gas methane, isn’t necessary to address climate change, according to University of Oxford researchers.
“It would be good if you maybe ate less beef, had less milk — but we don’t need to completely get rid of all the cows,” said John Lynch, postdoctoral researcher at the University of Oxford.
Lynch studies ways to anticipate the impacts of greenhouse gases and suggests that the greenhouse gas carbon dioxide is more important to address than methane. It takes much less time to reverse the impact of methane emissions than it does to undo the effects of carbon dioxide, so it’s possible to delay addressing methane, he said. His suggestion has huge implications, because the way greenhouse gases are reported and compared in policies today doesn’t make it clear how differently these gases behave.
The Global Warming Potential (GWP) is a metric used to compare how much different greenhouse gases will warm the atmosphere across a given period into the future. Organizations including the U.S. Environmental Protection Agency and U.N. Intergovernmental Panel on Climate Change publish the GWP in their reports.
However, Lynch’s research shows that, for some purposes, the GWP metric may be misleading. Reporting all gases as though they were on the same playing field, experts say, does not account for key differences between them, especially between methane and carbon dioxide.
“Metrics that try and treat the gases in the same way are always going to have limitations,” Lynch said.
In the first few decades after it’s emitted, methane causes more warming per kilogram than carbon dioxide does. Methane, however, breaks down after about 12 years, while carbon dioxide accumulates in the atmosphere, warming the planet for millennia.
Calculating warming potential over 100 years, for instance, does not account for how strongly methane warms the planet initially, nor does it account for the full effects that CO2 emissions will have.
So, if the GWP measurement is misleading, what does this mean for potential policies based on that statistic?
It would be best to cut both carbon dioxide and methane emissions, Lynch said. But because governments have limited will and resources to address the problem, he said it is more important to achieve net zero carbon emissions before cutting methane.
“If we prioritize the methane, first we will have a large quick benefit” as methane levels in the atmosphere rapidly fall, Lynch said. “But in the meantime, we will have carried on emitting all the CO2 that we decided not to bother with because methane looks easy. And then, in a couple of decades, we’ll be stuck with that CO2 warming, whereas if we just delayed our action on methane, we’d still be able to reverse that.”
Still, governments should not ignore methane emissions in climate policy, as all greenhouse gases warm the planet, Lynch said. But ultimately, the most important thing to do is to get to net zero carbon dioxide, because that’s the gas with the longest-lasting and biggest impact on global warming.
“There’s a lot of harm in delaying things that address carbon emissions,” said physicist Raymond Pierrehumbert, a professor and statutory chair in the physics department at the University of Oxford.
These long-lasting emissions will warm the planet, causing more extreme weather conditions, droughts, floods and rising sea levels. The longer it takes to reach net-zero CO2 emissions, the more severe these effects will be.
That’s why Lynch feels we “don’t really have a choice” on whether or not to decrease carbon emissions.
“All of your energy needs to be decarbonized,” Lynch said. “If we don’t, we’ll never stop the temperature going up.”
Carlyn Kranking and Grace Rodgers are Health, Environment and Science reporters at Medill. You can follow them on Twitter at @carlyn_kranking and @gracelizrodgers.
