Extreme heat waves in recent years have had severe impacts, causing heat- related deaths, forest fires, and harvest losses . The impacts of the extreme heat waves projected for a 4°C world have not been evaluated, but they could be expected to vastly exceed the consequences experienced to date and potentially exceed the adaptive capacities of many societies and natural systems . [my emphasis] Warming to 4 degrees would also lead to “an increase of about 150 percent in acidity of the ocean ,” leading to levels of acidity “unparalleled in Earth’s history .” That’s bad news for, say, coral reefs: The combination of thermally induced bleaching events, ocean acidification, and sea-level rise threatens large fractions of coral reefs even at 1.5°C global warming. The regional extinction of entire coral reef ecosystems, which could occur well before 4°C is reached, would have profound consequences for their dependent species and for the people who depend on them for food, income, tourism, and shoreline protection. It will also “likely lead to a sea-level rise of 0.5 to 1 meter, and possibly more, by 2100, with several meters more to be realized in the coming centuries.” That rise won’t be spread evenly, even within regions and countries — regions close to the equator will see even higher seas. There are also indications that it would “significantly exacerbate existing water scarcity in many regions , particularly northern and eastern Africa, the Middle East, and South Asia , while additional countries in Africa would be newly confronted with water scarcity on a national scale due to population growth.” Also, more extreme weather events: Ecosystems will be affected by more frequent extreme weather events, such as forest loss due to droughts and wildfire exacerbated by land use and agricultural expansion. In Amazonia, forest fires could as much as double by 2050 with warming of approximately 1.5°C to 2°C above preindustrial levels. Changes would be expected to be even more severe in a 4°C world. Also loss of biodiversity and ecosystem services: In a 4°C world, climate change seems likely to become the dominant driver of ecosystem shifts, surpassing habitat destruction as the greatest threat to biodiversity . Recent research suggests that large-scale loss of biodiversity is likely to occur in a 4°C world, with climate change and high CO2 concentration driving a transition of the Earth’s ecosystems into a state unknown in human experience. Ecosystem damage would be expected to dramatically reduce the provision of ecosystem services on which society depends (for example, fisheries and protection of coastline afforded by coral reefs and mangroves.) New research also indicates a “rapidly rising risk of crop yield reductions as the world warms .” So food will be tough.
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- Spring '16
- The American, People's Republic of China, Hu Jintao, South China Sea