Davos, Switzerland (CNN Business) The annual meeting of business and political leaders in Davos wrapped up Friday with two of the world's most powerful people disagreeing over how to address the climate crisis and youth activists excoriating the international elite for not doing enough to prevent global warming.

After a week of discussions at the World Economic Forum that were dominated by how to tackle the biggest problem the planet faces , the last big event of the conference produced a tense exchange between US Treasury Secretary Steven Mnuchin and Christine Lagarde, the president of the European Central Bank.

Mnuchin, who earlier this week questioned the credentials of climate activist Greta Thunberg, told panelists that long-term planning is futile when it comes to analyzing and containing climate change.

Lagarde disagreed. It was crucial to assess the risk that climate change poses to financial markets and the economy, she said, so it can be "anticipated, measured" and "hopefully mitigated."

Mnuchin rushed to respond. "Christine, I think you can have a lot of people look at this and model it," he said. "I just don't want to kid ourselves. I think there's no way we can possibly model what these risks are over the next 30 years with a level of certainty."

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