Prince William is scheduled to attend the COP30 climate summit in Brazil next month, as announced by palace sources.
The father and son duo appeared together on Thursday night at a gathering leading up to the climate summit, which is planned for in the Amazonian city of Belém.
The royal pair were present at the museum gathering, marking an rare public appearance together at a environmental conference preliminary meeting arranged together with the British authorities.
King Charles has been a long-time champion of biodiversity preservation - and Prince William has inherited the mission, with his own climate innovation awards, which will be hosted in Rio ahead of the climate conference.
Palace insiders have characterized William's involvement at the forthcoming conference as stepping up an important role in "climate diplomacy".
The King and Prince of Wales, making a joint entrance in the state Bentley, were introduced to guests including conservation experts, scientists, climate change campaigners, diplomats and government officials.
This participation included speaking in concert with French leader Macron of the French Republic and other global statesmen at the Ocean Finance Summit in Monaco earlier this year.
The COP30 summit will align with the prince's own sustainability recognition program, which will finish in the Brazilian city the eve of he attends the COP summit on 6 November.
Last week the royal figure referred to the Earthshot finalists as "contemporary champions".
King Charles has been a key figure at earlier environmental conferences, providing the introductory remarks in Dubai for the 28th Conference of Parties, including the observation: "The Earth does not belong to us, we belong to the Earth".
"For decades I've committed a large proportion of my life trying to warn of the existential threats facing us over climate change, environmental shifts and ecological decline," the monarch informed delegates.
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