Swedish climate activist Greta Thunberg, center, marches with other young climate activists outside the White House in Washington last week.

Swedish climate activist Greta Thunberg, center, marches with other young climate activists outside the White House in Washington last week.

Swedish climate activist Greta Thunberg, center, marches with other young climate activists outside the White House in Washington last week.

Swedish climate activist Greta Thunberg, center, marches with other young climate activists outside the White House in Washington last week.