By Edward McAllister DAKAR (Reuters) – African nations must help combat climate change and halt a rise in temperatures that is hitting crop yields and causing flooding and drought in the region, U.S. climate envoy John Kerry told a conference in Senegal’s capital on Thursday. At the African Ministerial Conference on Environment in Dakar, Kerry acknowledged that the 48 countries of sub-Saharan Africa emit only 0.55% of global harmful emissions, but said that every nation had to pull together in the face of crisis. “All of us are threatened by emissions – and Mother Nature does not care where th…