字幕表 動画を再生する 英語字幕をプリント Hey citizens of Earth, Trace here. Most climate scientists agree that climate change is happening and that humans are to blame. Greenhouse gasses like carbon dioxide and methane that we've been pumping into the atmosphere have been capturing heat from the sun's rays, and average annual temperatures have been on the rise since the industrial revolution. The common wisdom is we need to drastically cut back the amount of greenhouse gasses we emit, but what if instead we just reduced the amount of sunlight we receive so greenhouse gasses can't soak up as much heat? If that sounds crazy to you, it's probably because it kind of is. Projects that would accomplish that would require engineering feats on a global scale, hence why it's called “geoengineering.” Geoengineering ideas to fight climate change stretch all the way back to 1965 when science advisors to President Lyndon B Johnson proposed covering 13 millions square kilometers of ocean with reflective particles to bounce 1% of the sun's rays back into space. As you can tell by how un-fabulous our oceans are right now, we never ended up glitter bombing the Pacific. But geoengineering ideas still crop up from time to time, lurking at the fringe of the climate change discussion. They run the gamut from painting everyone's roof white, to drone ships that make ocean clouds brighter, to launching a giant mirror into space. All of these plans have one thing in common though: They're all trying to increase the Earth's albedo, which is a measure of how much light we reflect back into space, as well as the name of my hispanic alter ego. There are a lot of reasons none of these ideas have gained any ground though. First, as you might imagine, intentionally changing the entire world would be kind of expensive. And in a time when the scientific community is STILL trying to convince the powers that be that climate change is both a real and serious threat, it's going to be hard to get those same powers to shell out funding for something crazy like a mirror in space. Ironically, the cost of these projects will likely be relatively small compared to fixing the damage caused by climate change in the long run. Second, these ideas may have side effects that would change the world in unintended ways. One of the most popular and realistic geoengineering proposals is to release sulfate particles into the air, which would combine with water vapor to form aerosols that reflect sunlight. Large volcanic eruptions do the same thing and cause temperatures to dip for a few years. Unfortunately, these sulfates also react with chlorine in the atmosphere, converting it to a form that destroys the ozone layer. Basically these geoengineering projects might be like that time you tried to fix your car yourself, and it worked for a bit until it broke in a more expensive way. But the biggest reason geoengineering still isn't considered the solution to climate change is because it doesn't solve the root of the problem, if anything it encourages us to never actually fix it. We have a hard enough time changing our lifestyles now, and if people learned that we could spray sulfates in the atmosphere every few years and we could keep burning coal, oil, and natural gas, why would anyone change? And if we don't curb the rate we put greenhouse gasses into the atmosphere, then the problem will only get worse, and the situations we'll have to engineer our way out of will get more extreme. Another ambitious geoengineering idea sprung up lately: replenishing arctic ice with millions of windmills. Jules gets into the details here. So knowing the risks and rewards of geoengineering, are you on board or do you think we should focus on cutting emissions. Let us know in the comments and come back here every day for more. Thanks for watching!