Increasing atmospheric helium due to fossil fuel exploitation

Fossil fuels contain small amounts of helium, which are co-released into the atmosphere together with carbon dioxide. However, a clear build-up of helium in the atmosphere has not previously been detected. Using a high-precision mass spectrometry technique to determine the atmospheric ratio of helium-4 to nitrogen, we show that helium-4 concentrations have increased significantly over the past five decades. Obtaining a direct measure of the rise in atmospheric helium-4 is possible because changes in nitrogen are negligible. Using 46 air samples acquired between 1974 and 2020, we find that the helium-4 concentration increased at an average rate of 39 +/- 3 billion mol per year (2 sigma). Given that previous observations have shown that the ratio between helium-3 and helium-4 in the atmosphere has remained constant, our results also imply that the concentration of helium-3 is increasing. The inferred rise in atmospheric helium-3 greatly exceeds estimates of anthropogenic emissions from natural gas, nuclear weapons and nuclear power generation, suggesting potential problems with previous isotope measurements or an incorrect assessment of known sources. Mass spectrometry measurements show that the concentration of helium in the atmosphere has risen over the past five decades due to fossil fuel emissions.

Automated summary

Using a high-precision mass spectrometry technique, researchers have found that the concentration of helium in the atmosphere has significantly increased over the past five decades due to fossil fuel emissions. This finding also implies an increase in the concentration of helium-3, exceeding estimates of anthropogenic emissions.