GEF

Unit 1  |  Why Water Matters 27 carbon dioxide (CO 2 ) from burning fossil fuels , is responsible for an observed increase of 1.4 degrees Fahrenheit (0.8 degrees Celsius) in global average temperature over the past 100 years. Climate scientists predict further increases of between 3 and 7 degrees Fahrenheit (1.6 to 3.9 degrees Celsius) before the end of the century. Droughts around the globe are causing rivers and lakes to dry up. Climate change is increasing water insecurity in much of the world by intensifying droughts, floods, and extreme weather events. Increased temperatures are melting glaciers that sup- ply water to many regions of the world, such as India and the western U.S. Sustainability requires both sharply reducing GHG emissions and adapting to the increased water instability caused by climate change. As a response to these trends, scientists and sustainability advocates have popularized the concept of peak water , which emphasizes that when water is used unsustainably, it becomes increasingly scarce. This concept is borrowed from peak oil, the understanding that production from oil reserves inevitably declines once the maximum rate of extraction is passed. CARBON DIOXIDE (CO 2 ) A gas that is the most com- mon form of atmospheric carbon, used by plants in photosynthesis, and emitted during the combustion of carbon based fuels such as petroleum. FOSSIL FUELS Nonrenewable carbon-based fuels, such as oil, coal, and natural gas, formed from the decomposition, geological compression, and heating of organic material. PEAK WATER A concept that emphasizes that accessible, clean water is being used unsustainably and is becoming depleted and unavailable over much of the planet.