Around 150 climate change protesters inflated a "carbon dinosaur" outside Scotland's biggest oil refinery, at Grangemouth, near Falkirk, north of Edinburgh.
They also waved blue sheets beneath cardboard mock-ups of the G8 leaders as mermaids to highlight the threat of rising sea levels.
The activists then paraded about with a homemade octopus and chanted "Oil fuels climate change", while BP employees peered through office windows.
The campaigners handed in an open letter for Ralph Alexander, the chief executive of Innovene, the subsidiary of BP that runs the plant, accusing oil companies of destroying the world's climate.
The letter said that oil firms were responsible for the bulk of carbon emissions, which "could tip the climate into unstoppable chaos".
It also warned that Grangemouth itself could be submerged in water in 50 years as sea levels rose because of climate change.
Duncan McLaren, chief executive of Friends of the Earth Scotland, told cheering protesters: "We are here in the belly of the beast.
"It's not good enough for George Bush to say he's going to put Americans first, because what he actually means is that he's going to put the oil industry first.
"The next 10 to 15 years is going to be critical. Unless something is done now, irreversible levels of climate change will take place leaving 3 billion people with dire shortages of food and water."
