Emissions of carbon dioxide from the burning of fossil fuels have ushered in a new epoch where human activities will largely determine the evolution of Earth's climate. Because carbon dioxide in the atmosphere is long lived, it can effectively lock the Earth and future generations into a range of impacts, some of which could become very severe. Therefore, emissions reductions choices made today matter in determining impacts experienced not just over the next few decades, but in the coming centuries and millennia. Policy choices can be informed by recent advances in climate science that quantify the relationships between increases in carbon dioxide and global warming, related climate changes, and resulting impacts, such as changes in streamflow, wildfires, crop productivity, extreme hot summers, and sea level rise.The report includes the following table summarizing the relationship between CO2 levels in the atmosphere and the average amount of warming expected.
OK. But what do those levels of warming mean? Well, the report provides some answers to that question, too. For each degree of warming there will be1
- 5-10% less rainfall in Mediterranean, southwest North American, and African dry seasons.
- 5-10% more rainfall in Alaska and other high latitude areas in the northern hemisphere.
- 3-10% more heavy rainfall in most areas.
- 5-10% less streamflows in some river basins, including the Arkansas and the Rio Grande.
- 5-19% less corn production in the US, Africa, and India.
News release from NAS about the report.
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1These estimate apply for a 1-4°C warming. If there is more warming than that, the consequences are less easy to predict, but the changes are likely to be larger than those associated with a 4°C warming.