Now Playing: The best way to survive the heat on a hot day in Beijing Now Playing – China’s newest skyscraper is just one of several buildings in the country to be demolished Now Playing The best ways to survive a flu pandemic Now Playing New research suggests that the flu may be more contagious in places with high temperatures Now Playing Trump’s latest trade war with China is a mistake Now Playing Former Trump administration official: Trade war with Beijing is the dumbest thing he’s ever done Now Playing China’s top lawyer says China should give back to America Now Playing President Donald Trump says he has a ‘great relationship’ with Xi Jinping, but it’s not ‘close’ Now Playing In-depth: Trump talks about China trade war and trade policies with Chinese President Xi Jinping Now Playing ‘We are in a very good place’: Former Trump adviser on his transition team’s decision to leave Now Playing What Trump says about the ‘birther’ issue now that he’s in office Now Playing Why President Trump was so quick to attack the ‘tremendous pressure’ on him Now Playing US to lift tariffs on Chinese goods by mid-July Now Playing Donald Trump’s immigration ban will fail, but could be overturned by Congress Now Playing How Trump’s first 100 days have changed Washington’s foreign policy Now Playing CNN’s Anderson Cooper on the fallout from Trump’s executive order on immigration Now Playing Ivanka Trump’s fashion line has a new ‘fashion house’ Now Play The Trump administration says the travel ban will not affect U.S. workers in the Middle East Now Playing Who is in charge of the Iran nuclear deal?

Now Playing This year’s U.N. climate summit: Trump or China?

Now Play This year in science Now Playing World leaders to meet in Paris for climate summit Now Playing A new book shows that women are more likely to have breast cancer Now Playing U.K. PM says Brexit has ‘no precedent in human history’ Now Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE