Greenhouse gas levels have hit yet another record – here's why

James Dinneen is a writer.

Concentrations of carbon dioxide, nitrous oxide and methane reached record highs in the atmosphere in 2021.

The atmospheric concentrations of key greenhouse gases were measured at more than 100 monitoring sites by researchers at the World Meteorological Organization.

The amount of carbon dioxide in the atmosphere increased on average by 2.5 parts per million. The amount of nitrous oxide went up by 1.3 parts per billion. The average year-to-year increase over the previous 10 years was slightly higher.

Since researchers started keeping records 40 years ago, the biggest single-year increase has been for methane. More than two and half times pre-industrial levels of atmospheric methane were reached between 2020 and 2021.

The Secretary-General of the WMO said in a press release that we are heading in the wrong direction.

Taalas said steps to reduce methane emissions should be taken without delay.

What is causing the record levels?

The rise in carbon dioxide and nitrous oxide is well known. Fossil fuels and cement production have led to an increase in carbon dioxide. Nitrogen Fertiliser, burning fossil fuels and industrial processes are some of the reasons for the rise in nitrous oxide. Natural sources of nitrous oxide includeMicrobes in the ocean.

Researchers haven't been able to explain why methane concentrations have risen.

60 percent of atmospheric methane comes from sources like oil and gas production and waste rotting in landfills. Wetlands are a major natural source of methane. It is difficult to distinguish what is behind the rise due to the fact that many of the sources are overlap and there is no data.

A biological source is suggested by the ratio of carbon isotopes in methane. The models suggest that tropical wetlands may be to blame for the increase in emissions due to warmer temperatures and changing precipitation. The role of that climate feedback is not certain.

Changes that affect how methane is broken down in the atmosphere may contribute to the rise. It will take more modelling to crack the methane mystery, according to the authors of the report.