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Temperatures are rising, and greenhouse gases are being emitted faster than ever. What's a planet to do? Hank explains the recommendations of some of the world's top scientists to stem global warming.

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[intro music]


Since you're here with us watching SciShow, I'm gonna go on a limb and guess that you're not a big skeptic about the climate change. Of course, whether you understand or not, it's happening. Though not understanding it could be a particularly big deal if you happen to be a country. Or someone in charge of one. Which is why we have the Intergovernmental Panel on Climate Change, an international group of researchers from all kinds of disciplines to provide neutral scientific information about climate change for the governments of the world. Its first assessment report was published in 1990, and key policy makers all over the world have been more or less ignoring them ever since.

This week the IPCC released its latest report written by 235 scientists from 58 countries. But, instead of just laying out data about the mess that we're in, this time they also tell us what we need to do in order to save ourselves from ourselves. And the report has gotten a lot of attention, because a few of the suggestions seem pretty radical to some, but they might turn out to not be radical enough.

 The crux of the matter

According to their findings emissions of carbon dioxide, the most prevalent greenhouse gas, increased faster between 2000 and 2010 than it did over the previous thirty years - the fastest in human history. Over the past decade we've released the equivalent of one gigatonne of CO2 each year, even after all the steps we've taken to try to cut our emissions. Because of this, the scientists say by the end of the century global surface temperatures are set to increase between 3.7 and 7.8 degrees Celsius from their pre-industrial levels. 7.8 degrees, by the way, would be almost three degrees worse than the worst-case scenario predicted by the IPCCs inaugural report nearly twenty five years ago.

In order to even have a 50-50 chance of avoiding the agreed-upon danger threshold of a two degree increase, we need to triple the proportion of energy we're getting from low-carbon sources. Which, obviously, is not going to be easy. Nearly 40% of the world's energy still comes from coal, and only about 0.11% of the energy in the United States comes from solar power.

But we do have options. If we choose to use them.

 Options (02:07)

One of the IPCC urges is carbon capture and storage or CCS, which has the potential to make fossil fuels like coal and natural gas safe for continued use at least for the next few decades. In CCS you take the exhaust from fossil fuel burning plants and pass it through a solvent that binds to CO2. While the rest of the gas is vented, the CO2-rich solvent is drawn off, and the carbon dioxide can then be used for making stuff. Like fertilizer. Or buried under a layer of impermeable rock. The point is: it stays out of the atmosphere.

But according to the report we've reached the point where we not only need to reduce our emissions, we also need to start sucking CO2 back out of the air. The most effective way of doing that is by letting trees do what trees do best and clean up our mess for us. So the IPCC is emphasizing afforestation, which as opposed to reforestation involves planting forests where there had been none before. This is one of the cheapest solutions available, they point out, and could save us a gigatonne or more per year of CO2.

But afforestation would mean setting aside land that we'd otherwise be using for farming or building strip malls or whatever, which some countries I know might have a hard time with. So the IPCC also proposes planting bio-energy crops which not only collect CO2, but can be burned as fuel. Fast-growing plants like sugar cane and tropical grasses are good biofuels, but we have to capture and store the carbon when we burn it.

And then... there's the nuclear option. The report's authors point out that nuclear energy makes sense from a global warming perspective. But they also point out that there, you know, are all those risks, including the safety of the power-plants themselves and being stuck with radioactive waste for tens of thousands of years.

The next ten to twenty years are really our last opportunity to make big changes before a depressing situation turns into a catastrophic one. I don't know about you, but I'm kinda liking the Earth the way it is now, and even though humans are really screwing this up, I'd like to keep living as well, so let's try to make this happen.

 Closing notes

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