The National Academy of Sciences is today releasing a new report, Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millenia, which finds that continued emissions of greenhouse gases will lock in higher global temperature increases. The press release offers these details from the report:
Although some important future effects of climate change are difficult to quantify, there is now increased confidence in how global warming of various levels would relate to several key impacts, says the report. It lists some of these impacts per degree Celsius (or per 1.8 degrees Fahrenheit) of global warming, for example (these apply for 1 C to 4 C of warming):
* 5 percent to 10 percent less total rain in southwest North America, the Mediterranean, and southern Africa per degree Celsius of warming.
* 5 percent to 10 percent less streamflow in some river basins, including the Arkansas and Rio Grande, per degree Celsius of warming.
* 5 percent to 15 percent lower yields of some crops, including U.S. and African corn and Indian wheat, per degree Celsius of warming.
While total rain is expected to decrease in some areas, more of the rain that does occur is expected to occur in heavy falls in most land areas (3 percent to 10 percent more heavy rain per degree Celsius). In addition, warming of 1C to 2 C (1.8 F to 3.6 F) could be expected to lead to a twofold to fourfold increase per degree in the area burned by wildfire in parts of western North America, the report says. Warming of 3 C (5.4 F) would put many millions more people at risk of coastal flooding and lead to the loss of about 250,000 square km of wetlands and drylands. And warming of 4 C (7.2 F) would lead to far warmer summers; about nine out of 10 summers would be warmer than the warmest ever experienced during the last decades of the 20th century over nearly all land areas.
… Emissions reductions larger than about 80 percent, relative to whatever peak global emissions rate may be reached, would be required to approximately stabilize carbon dioxide concentrations for a century or so at any chosen target level.
Further, stabilizing atmospheric concentrations does not mean that temperatures will stabilize immediately. Warming that occurs in response to a given increase in the CO2 concentration is only about half the total warming that will ultimately occur. For example, if the CO2 concentration stabilizes at 550 ppmv, the Earth would warm about 1.6 C on the way to that level; but even after the CO2 level stabilizes, the warming would continue to grow in the following decades and centuries, reaching a best-estimate global "equilibrium" warming of about 3 C (5.4 F).
Just one observation, climatologists still hotly dispute (adverb, bad as it is, intended) whether or not the planet was 2 to 4 degrees warmer on average than it is today during the Holocene Climatic Optimum, some 6,000 to 9,000 years ago.
Go here for the whole report.