Measure of Global Emissions off by 5.5 Billion Tons

Our Daily Planet

On the heels of President Biden's Earth Day climate summit, scientists have identified a 5.5-billion-ton discrepancy in global carbon emissions counts. This gap is roughly as large as the annual emissions of the United States and threatens to disrupt carbon emissions reductions goals worldwide. But how did the world's nations undercount emissions by so much? Experts say that inconsistent measuring and reporting methods are most likely to blame, along with some serious exaggeration.

Why This Matters

Nearly every nation in the world has presented a Nationally Determined Contribution (NDC) for the Paris Agreement -- and many have made commitments to reach net-zero emissions by 2050. Experts say that meeting these goals is crucial to preventing catastrophic temperature rise. But even as nations rally, deforestation and ocean acidification have increased, destroying essential carbon sinks. Accurately counting emissions while tracking carbon sequestration is complex and may not always provide the best optics for governments. But if countries fail to measure emissions, the world risks painfully undershooting its emissions targets.

Counting Trees

Christopher Williams, a forest expert at Clark University, says that this study:

...draws attention to something that has concerned many of us for quite a while -- that our national greenhouse gas inventory reporting is not designed to measure and monitor true mitigation.

Williams explains that this discrepancy can be traced back to some UN reporting rules surrounding "managed land" like national parks and regions with intensive forestry. These rules require countries to report how human activity impacts carbon emissions or sequestration from this land. But indirect factors, like atmospheric carbon stimulating forest growth, can be difficult to measure and separate from direct impacts. This challenge has led countries to create their own individual measurements, and emissions impacts of "managed land" can be very inconsistent from country to country. Giacomo Grassi, a forest expert at the European Commission's Joint Research Centre and lead author of the study, explains that independent energy system modelers use one technique to measure emissions. Still, a country's own scientist may use another.

Additionally, by reporting these indirect impacts, countries can take credit for indirect improvements rather than intentional policy or action. "There will be some policy and management in there, but a lot of it is going to be a free lunch," said Glen Peters, research director of the Center for International Climate Research in Oslo. By counting carbon sinks, some countries can claim net zero without implementing policies to prevent accelerating emissions which could harm their carbon sinks and lead to an emissions crisis in the future. But Grassi says there is an easy fix. Simply adjusting and standardizing measurement methods could help countries more accurately measure their direct emissions and reductions. "In the absence of these adjustments," the study states, "collective progress would appear to be more on track than it actually is."


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