WASHINGTON — President-elect Donald J. Trump, who has called climate change a hoax perpetrated by the Chinese, met on Monday with the climate-activist extraordinaire Al Gore, offering environmental activists a glimmer of hope that the Trump administration’s policies will moderate from his campaign pledges to scrap all efforts to stem the warming of the planet.

But even as the president-elect was sitting down with the former vice president, his transition team continued to court ardent opponents of climate control policies to fill key posts in the government. Many transition officials question or deny the established science of human-caused climate change and have worked aggressively to undo President Obama’s climate change policies.

Mr. Gore, who starred in the Academy Award-winning documentary “An Inconvenient Truth,” projected optimism in the lobby of Trump Tower, telling reporters that his meeting with Mr. Trump was “lengthy and very productive,” and calling it “a sincere search for areas of common ground.”