Reducing carbon dioxide alone will not limit global temperature rises to 1.5C; we have to limit methane emissions too. The global methane pledge could therefore be one of the biggest achievements from the Glasgow climate conference.

Cutting methane has a double benefit. In addition to contributing to climate heating, methane is also one of the main gases that causes ozone to form in the lower atmosphere, where it harms our health and damages our crops. The global pledge is the first step to a 45% reduction target. The United Nations Environment Programme estimates that the decreased ozone that would follow would prevent 255,000 early deaths, 775,000 asthma-related hospital visits and 26m tonnes of crop losses globally each year.

Prof Mathew Heal, of the University of Edinburgh, said: “Targeting local and regional energy and transport will not be sufficient to achieve substantial ozone air quality benefits in the UK and Europe without also targeting methane sources. If methane concentrations continue to rise, average ozone will increase, and vice versa.”

Methane from waste decaying in landfill sites can be captured and flared or used to generate electricity. Travel to a historical coalmining area and you will meet communities that have lost loved ones in explosions from what the Victorians called “fire-damp”. This methane emitted from coalmines looks set to increase as modern pits become deeper. However, it can be removed from vents, and old mines can be flooded. Changes to the ways that rice is grown, modified animal feeds, better treatment of manure and less crop burning are all needed along with decreasing food waste and meat consumption.

The biggest benefit could come from the petroleum and fossil gas industries, where stemming leaks would increase revenue. Individual leaks on wells and pipes may be small but their total is huge. Leakages from the US fossil gas industry have been measured as far away as the Swiss Alps and in Cape Verde.

Fossil gas also contains ethane, which is far more potent in forming ozone. Prof James Lee, of the University of York, said: “Air pollution around fracking operations in the US is highly sensitive to gases such as ethane, which contributes about 50% to the ozone production. Prioritising leaks from fossil gas would have the added benefit of helping to limit local ozone. This is likely to be true in the UK too.”

India has experienced the greatest rise in ozone and experiences the greatest health impact and crop losses of any country. It has not signed the global pledge.