There will be serious consequences if climate change is not tackled, according to the managing director of the International Monetary Fund (IMF).

"As I've said before, if we don't do anything about climate change now, in 50 years' time we will be toasted, roasted and grilled," Christine Lagarde said during a panel discussion Tuesday at the Future Investment Initiative in Riyadh, Saudi Arabia.

"Decisions are needed at this point in time, which will probably mean that in 50 years' time oil will be a secondary commodity," Lagarde added. She said this was something that was "well understood" in the Kingdom.

Both climate change and inequality were "two key issues" that would drive us to either utopia or dystopia, Lagarde stated. "If we don't address those two issues — of climate change and growing inequalities — we will be moving towards a dark 50 years from now," she said.

Speaking on the same panel as Lagarde was Amin Nasser, president and CEO of Saudi Aramco.

"Alternatives, electric cars and renewables, are definitely gaining market share, making a lot of progress and we are witnessing that," he said. "However, it will be decades before they take a major share of the global energy supply."