Global warming is the ongoing rise of the average temperature of the Earth’s climate system and has been demonstrated by direct temperature measurements and by measurements of various effects of the warming. It is affecting many ecosystems and organisms, but not in a good way. Global warming could cause many species to become extinct. Forests, farms, and cities will face troublesome new pests, heat waves, heavy downpours, and increased flooding. All those factors will damage or destroy agriculture and fisheries.