President Donald Trump's 100th day in office is being marked with protests across the United States.
Tens of thousands of people are marching in Washington DC alone, calling for action on climate change.
When he took office, Mr Trump moved swiftly to reverse Obama-administration environmental policy. Regulations on fossil fuels were repealed, the Keystone XL pipeline was approved and if passed, Mr Trump's budget will cut funding to the Environmental Protection Agency by a third. He has promised to leave the Paris Climate Agreement.
The climate demonstration is the latest in a series of protests against the new administration. Huge crowds gathered around the world to march for women's rights in January, and Mr Trump's travel ban saw protest action at airports across the United States.
During the march, temperatures are expected to reach a new record of 32degC Washington DC.
New climate legislation which would entirely phase out fossil fuels through a transition to renewable energy by 2050 was unveiled by Democrats on Thursday. At the rally on Capitol Hill, Bernie Sanders called on Mr Trump to listen to scientists.
"Donald Trump is wrong about a lot of things. But there is no area where he is more wrong than on the issue of climate change."
The legislation is unlikely to make headway through a Republican-controlled Senate which largely remains unwilling to acknowledge human contribution to climate change.
Actor and environmentalist Leonardo DiCaprio was among those spotted at the march in Washington DC. He tweeted he is "honoured to join indigenous leaders and native peoples as they fight for climate justice".