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This is Scientific American's 60-second Science, I'm Annie Sneed.

这里是科学美国人——60秒科学系列，我是安妮·斯尼德。

Solar. Wind. Hydropower. These renewable energy sources are all much better for the climate than fossil fuels, right? Well, yes for wind and solar. But it turns out that the picture for hydropower is more complicated than we think.

太阳能发电。风能发电。水力发电。相比化石燃料，这些可再生能源都要更有利于气候，对吧？嗯，风能和太阳能确实如此。但事实证明，水力发电的情况比我们想象的要复杂。

A new study by the Environmental Defense¹ Fund analyzed² the climate impacts of 1,500 hydropower facilities across the globe. That accounts for about half of hydropower generation worldwide. The researchers looked at whether the facilities behave as a greenhouse gas sink or as a source. To figure this out, they investigated all the different components³ that help determine a hydropower facility's greenhouse gas emissions⁴.

美国环保协会的一项新研究分析了全球1500座水电设施产生的气候影响。这些设施的发电量大约占到全球水力发电总量的一半。研究人员的观察重点是：这些设施相当于温室气体汇还是温室气体源。为了找出答案，他们调查了有助于确定水电设施温室气体排放量的所有不同因素。

"There are so many factors that contribute to greenhouse gas emissions from hydropower—but essentially⁵, the majority of greenhouse gas emissions arise from the reservoir itself, as vegetation and soils are submerged underwater in the dam that is used for the hydropower generation."

“导致水力发电排放温室气体的因素非常多，但基本上来说，大部分温室气体排放源于水库本身，因为植被和土壤淹没于水电大坝的水下。”

Ilissa Ocko, a senior climate scientist at the Environmental Defense Fund and co-author of the study. As the submerged vegetation decays, it releases methane⁶ or CO2.

美国环保协会的气候高级科学家伊利莎·奥克说到。水下植被腐烂后，会释放出甲烷或二氧化碳。

"The larger the surface area of the reservoir, the more greenhouse gases are going to be emitted from that reservoir. Also, the temperature plays a role as well—how warm the reservoir is will affect how much greenhouse gases are produced and emitted from the reservoir."

“水库的表面积越大，排放的温室气体就越多。此外，温度也会产生作用，水库的温度会影响温室气体的产生量和排放量。”

Through their analysis, Ocko and her co-author Steven Hamburg, also with the Environmental Defense Fund, discovered that the climate impacts of hydropower run the gamut⁷. The good news is that some facilities perform just as well as wind and solar. But shockingly, more than 100 facilities are actually worse for the climate than fossil fuels. The study is in the journal Environmental Science & Technology.

通过分析，奥克及其合著者——同样来自美国环保协会的史蒂芬·汉堡发现，水力发电会在各个方面产生气候影响。好消息是，一些水力发电设施的表现与风能和太阳能一样好。但令人震惊的是，有100多座设施对气候的影响比化石燃料还要严重。这项研究发表在《环境科学与技术》期刊上。

This finding doesn't mean we should forget about hydropower.

这一研究结果并不意味着我们应该放弃水力发电。

"But we just need to be careful to make sure that we have climate benefits. There are a lot of situations where hydropower can be on par⁸ with wind and solar. So it really depends on the specific facility."

“我们只要小心谨慎，确保我们获得气候效益就行。在很多情况下，水力发电能与风能和太阳能不相上下。因此，水力发电的环保情况因具体设施而异。”

Thanks for listening for Scientific American — 60-Second Science. I'm Annie Sneed.

谢谢大家收听科学美国人——60秒科学。我是安妮·斯尼德。