For a landmark moment in the global effort to stave off catastrophic climate change, Joe Biden’s “climate day” at the White House was rather low-key. The first 10 days of Biden’s presidency have represented a startling handbrake turn from Donald Trump’s term, where climate science was routinely disparaged or sidelined and policies to cut planet-heating emissions were jettisoned. But emissions won’t get to zero via presidential action alone and Democrats’ hopes of sweeping climate legislation appear remote in a finely balanced Senate where climate denialism is still rife, as demonstrated on Tuesday by the Republican senator Rand Paul promoting a baseless theory that global heating is caused by the Earth’s tilt rather than human activity.