China and the United States have signed a joint declaration to address the global climate crisis during the next decade, marking one of the most significant breakthroughs yet to come out of the United Nations Climate Change Conference of the Parties, or COP26, in Glasgow, Scotland.The declaration, which is called the US-China Joint Glasgow Declaration on Enhancing Climate Action in the 2020s, was announced on Wednesday evening by China's special climate envoy, Xie Zhenhua, and US special presidential envoy for climate, John Kerry.