Why have methane and nitrous oxide emissions gone down?
They have only dropped a little. For methane, the drop is mainly thanks to programmes that capture the methane gas seeping from rotting landfill sites and burn it, sometimes making usable energy (and carbon dioxide). Fertilizers and agricultural processes are the largest source of nitrous oxides, but there hasn’t been a clear long-term trend either way in these emissions. One reason for the recent dip has been introducing technologies to limit nitrous oxide emissions from cars and trucks.
