King Charles and Prince William make joint appearance showing support for upcoming COP30 summit

Britain's King Charles and heir Prince William made a rare joint appearance on Thursday to show support for the upcoming COP30 climate summit, at a time when a U.S.-led retrenchment has raised questions about how much the event can achieve.

Political leaders from across the world, climate campaigners and big business will gather in Brazil in four weeks' time for the United Nations talks which aim to secure more ambitious action - and finance - to tackle rising global temperatures.

But these will take place amid increased pushback by some world leaders that threatens to fragment the global consensus on climate, driven by factors like resistance to the cost of subsidising green energy projects and a prioritisation of defence spending.

Last month, U.S. President Donald Trump told the U.N. General Assembly that climate change was "the greatest con job" in the world.

In Britain, the leader of the main opposition Conservative Party said on Wednesday she would support more oil and gas extraction from the North Sea, while Reform UK, which is leading in opinion polls, has said it would impose taxes on the renewable energy sector and would scrap net zero targets.

Charles has for years campaigned about the environment and sustainability, well before the issue became mainstream, and has attended many previous COP meetings, although William's office announced on Thursday that the prince would take his place at this year's event.

William launched the Earthshot Prize in 2020 which seeks to find solutions towards fixing environmental problems within a decade. This year's awards ceremony will be held in Brazil shortly before the COP summit.

The two royals on Thursday attended a "Countdown to COP30: mobilising action for climate and nature" event at London's Natural History Museum where they met the Brazilian ambassador to London and viewed displays which showcased British-developed solutions for climate change.

"For more than five decades, the king has also used his unique platform to champion sustainability, emphasising the fundamental connection between humanity and nature," Buckingham Palace said.