Charles will issue a dire environmental warning to the world and say how nations have "less than 100 months to act" before the damage caused by climate change becomes irreversible.
The world is experiencing an economic slowdown but in his speech in Rio de Janeiro, the prince will say that in a recession people must not lose sight of the importance of continuing to combat global warming and protect the environment.
Charles will also talk about the importance of the business community joining the fight against climate change.
The address follows a series of speeches over the past 12 months where the prince has highlighted his growing concerns about the state of the planet.
Charles and the Duchess of Cornwall are touring South America and have already visited Chile and will spend a further three days in Brazil before travelling to Ecuador and its Galapagos islands.