Thursday is World Earth Day. To mark it, some 40 top global political figures, including China's President Xi Jinping, plan to attend U.S. President Joe Biden's virtual "Leaders Summit on Climate." For more on that, CGTN's Global Watch spoke to Professor Ho Kin-Chung. He is the director of the Polar Research Institute of Hong Kong. The professor expects a high level of cooperation among different countries to be one of the outcomes out of the summit. He said that their cooperation is very important.