题型:阅读理解 题类:模拟题 难易度:普通
河南省八市重点高中联盟“领军考试”2019届高三英语第三次测评试卷
Nearly 20 U.S. states have started carrying out former president Barack Obama's Clean Power Plan, which places limits on carbon dioxide emissions from power plants in an effort to reduce the impacts of climate change. The plan has been in legal limbo (边缘) for the past year. Yet scientists have now calculated another outcome of the policy: harm to crop yields (产量) if the plan is cancelled. Along with carbon pollution, coal-fired power plants spew (喷出) pollutants that form what we know as smog. The contribution of smog to increased rates of asthma (哮喘) and premature deaths was already known. The new research estimates the extent to which smog, under air-pollution policies-4n place before the Clean Power Plan, would limit production in 2020 of four major crops: corn, cotton, potatoes and soybeans.
Led by environmental engineer Shannon L. Capps, now at Drexel University, the team also sketched the extent to which those crop production losses would reduce under three nationwide scenarios (方案). One improved the efficiency of individual power plants. Another modeled a policy similar to the Obama plan, setting state CO2 emissions goals for the electricity department. A third established a tax on carbon emissions, under which emissions fell the most. But the greatest drop in smog-forming pollutants—and greatest gains in crop yields—came from policies such as the Clean Power Plan.
Researchers calculated how well each scenario would reduce the potential productivity loss (PPL) of each crop. PPL is a projected value for 2020 and indicates how much crop growth would suffer because of smog. Scenario 2 most closely agrees with results expected from the Clean Power Plan.
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