The idea of mainstreaming climate action into other policies gained traction in the European Union (EU) in the years running up to the Paris Agreement of 2015. It is increasingly recognised that mainstreaming climate change considerations into a wide range of policies is unavoidable if we want to cope with the huge challenge ahead. There is an important opportunity in extending and reviewing environmental legislation to incorporate climate concerns. International agreements often trigger the initiation of EU policy development. Short-lived climate forcers are pollutants that stay in the atmosphere for a limited number of years while having a significant impact on the climate because of their high global warming potential. In the wastewater sector, methane emissions are expected to remain more or less constant through to 2050 at a level of around 40 million tonnes of carbon dioxide-equivalent. Black carbon particles enter the atmosphere around the world from sources including the burning of household firewood, other biomass and coal.