Climate Change Diplomacy and Development Act of 2020 This bill requires the Department of State, in coordination with the U.S. Agency for International Development (USAID) to develop a Joint Department of State and USAID Strategy to Address the Global Climate Change Crisis. The State Department must also designate its Bureau of Oceans and International Environmental and Scientific Affairs to coordinate State Department and USAID efforts to guide U.S. foreign policy related to global climate change. Further, the State Department must include specified climate-related items and estimates in its annual budget request.