OSLO—Norway Prime Minister Erna Solberg plans to increase the Scandinavian nation's $840 billion oil fund's exposure to renewable energy, reflecting a continuing shift toward using its vast wealth to combat climate change.

Norway, possessing the largest sovereign-wealth fund in the world, currently devotes a fraction of its assets to green investments. Ms. Solberg told reporters Thursday "we will expand the mandate" in effort to more acutely combat global warming, but didn't specify how much more money will be devoted...