{"id":56,"date":"2007-04-03T14:45:11","date_gmt":"2007-04-03T19:45:11","guid":{"rendered":"http:\/\/blogs.edf.org\/climate411\/2007\/04\/03\/global_dimming\/"},"modified":"2007-04-03T14:45:11","modified_gmt":"2007-04-03T19:45:11","slug":"global_dimming","status":"publish","type":"post","link":"https:\/\/blogs.edf.org\/climate411\/2007\/04\/03\/global_dimming\/","title":{"rendered":"What's Global Dimming?"},"content":{"rendered":"

Last week, Vic asked about the phenomenon of "global dimming" and its effect on global warming. Good question. Here’s the answer.<\/p>\n

"Dimming of the sun" or "global dimming" is not due to anything happening to the sun. It’s due to something happening on Earth that blocks the sun’s rays. Global dimming is important from a climate standpoint because less sunlight reaching the Earth creates a cooling effect.<\/p>\n

<\/p>\n

What causes global dimming? Most likely air pollution, in the form of tiny particles produced when we burn fossil fuels. Pollution particles block sunlight in two ways. First, they cause more water droplets to condense in the air, forming darker clouds that block light (see Columbia University article<\/a>). Second, some airborne particles – particularly aerosols – reflect sunlight on their own. <\/p>\n

The cooling effect of global dimming has significantly slowed global warming – ironic, since air pollution is by no means a good thing. From the Nova program, "Dimming of the Sun<\/a>" on PBS: "\u2026 more than half the warming effect of our greenhouse emissions has been masked by the cooling effect of particle pollution."<\/p>\n

The damage to health from air pollution prompted Congress to pass the Clean Air Act of 1970 (see history<\/a>), and other countries, especially in Europe, have followed suit. As a result, air pollution has gone down, global dimming has decreased, and global warming has noticeably accelerated – particularly since 1990. (See "Impact of global dimming and brightening on global warming<\/a>".)<\/p>\n

The recent IPCC reports (see description of IPCC<\/a>) say global warming is accelerating at a faster rate than many models predict. The reduction in air pollution, and therefore global dimming, may well be the reason. That said, many models now do account for global dimming, as noted in the RealClimate article "Global Dimming and climate models<\/a>".<\/p>\n

The phenomenon of global dimming has given some scientists an intriguing idea. If adding reflective particles can cool the planet, why not do it deliberately to counteract global warming? This strategy, called "geo-engineering", will be the topic of tomorrow’s post.<\/p>\n","protected":false},"excerpt":{"rendered":"

Last week, Vic asked about the phenomenon of "global dimming" and its effect on global warming. Good question. Here’s the answer. "Dimming of the sun" or "global dimming" is not due to anything happening to the sun. It’s due to something happening on Earth that blocks the sun’s rays. Global dimming is important from a …<\/p>\n","protected":false},"author":15,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[20],"tags":[],"coauthors":[],"class_list":["post-56","post","type-post","status-publish","format-standard","hentry","category-news"],"acf":[],"yoast_head":"\nWhat's Global Dimming? - Climate 411<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blogs.edf.org\/climate411\/2007\/04\/03\/global_dimming\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"What's Global Dimming? - Climate 411\" \/>\n<meta property=\"og:description\" content=\"Last week, Vic asked about the phenomenon of "global dimming" and its effect on global warming. 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