The Air Resources Board in California is the state's top climate authority. Among other things, it coordinates a carbon offset program in which heavy polluters can balance each ton of emissions above the legal limit by paying local forest owners who participate in the programme. But, a recent investigation shows significant flaws in how the CO2 storage capacity of trees is being calculated, cancelling out climate benefits and leading to an actual increase in CO2 pollution. Environmentalists and researchers have further raised concerns about conflicts of interest, as partner organisations in the state-led offset programme have a financial interest in approving as many new forest tracts as possible.