SFU professor Kirsten Zickfeld

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Assuming balance in CO2 emissions vs removals could skew climate targets: SFU research

June 22, 2021
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Changes in climate resulting from carbon dioxide (CO2) emissions into the Earth’s atmosphere are not equal to the climate changes from deliberate CO2 removals—and assuming such a balance could lead to different climate outcomes that may skew climate targets, according to new Simon Fraser University-led research.

“Because of the complexity of the Earth’s system, things are not as simple as “one ton of CO2 in, equals one ton of CO2 out,” says Kirsten Zickfeld, a distinguished professor of climate science in SFU’s Department of Geography, and lead author of a new paper published this week in the journal Nature Climate Change. “CO2 emissions are more effective at raising atmospheric CO2 concentration than CO2 removals are at lowering it.”

According to Zickfeld, this “asymmetry” implies that a larger amount of CO2 removal is required to compensate for a given amount of CO2 emissions if the atmospheric CO2 concentration is to remain unchanged.

Researchers used a series of climate model simulations to test whether the change in climate resulting from CO2 emissions and removals is asymmetric. Their results showed that the rise in the atmospheric CO2 concentration following an emission is larger than the decline following a removal of the same magnitude.

Findings of the study infer that balancing a given amount of CO2 emissions with an equal amount of CO2 removals could lead to a different climate outcome than avoiding the CO2 emissions.

“Our study suggests that assuming exact balance between CO2 emissions and an equal amount of CO2 removals in a net-zero framework risks blowing climate targets,” she says.

While Zickfeld says that balancing emissions with CO2 removals of the same magnitude could lead to different climate outcomes, further study is needed to learn more about the extent of this effect.