As President Donald Trump weakens one environmental rule after another, the deep green state of California has found a way to fight back: with a rocket. “With science still under attack and the climate threat growing, we are launching our own damn satellite,” declared Governor Jerry Brown, explaining that the craft will track emissions and share the results.

One of the pollutants the satellite will measure is methane, a potent greenhouse gas. Mr Brown’s declaration on Friday in San Francisco, came just two days after the Environmental Protection Agency in Washington said it wanted to relax methane rules. For California and Mr Brown, the satellite is not only about monitoring methane monitoring but also shows how much states can do themselves to fight climate change.

Fifteen months after the US pulled out of the Paris climate agreement, California is at the center of a growing coalition of mainly Democratic US states and cities that have vowed to work toward the Paris targets themselves — and are agitating for others to join them. “Because there is no federal leadership, states have to step up,” said Gina McCarthy, the former head of the EPA under Barack Obama. “And that’s a very good thing.”