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This episode is sponsored by Wren, a website where you calculate your carbon footprint. Sign up to make a monthly contribution to offset your carbon footprint or support rainforest protection projects: https://www.wren.co/start/scishow

We recently got an important update from the IPCC, the definitive source on the climate crisis. And while there's not a ton of good news, there are some bits of hope if we can ramp up our actions now.

Hosted by: Hank Green

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Sources:
https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Full_Report.pdf [PDF]
https://www.ipcc.ch/2021/08/09/ar6-wg1-20210809-pr/
https://www.nytimes.com/2021/08/09/climate/climate-change-report-ipcc-un.html

https://www.nature.com/articles/s41586-021-03737-3
https://www.sciencedirect.com/science/article/abs/pii/S1146609X09001209?via%3Dihub

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https://www.storyblocks.com/video/stock/approaching-planet-earth-szwalixegjc5wffxe
https://climate.nasa.gov/climate_resources/24/graphic-the-relentless-rise-of-carbon-dioxide/
https://climate.nasa.gov/climate_resources/265/video-antarctic-ice-mass-loss-2002-2020/
https://climate.nasa.gov/climate_resources/139/video-global-warming-from-1880-to-2020/
https://www.storyblocks.com/video/stock/close-up-of-earth-planet-from-day-to-night-transition-3d-render-animation-nasa-images-world-globe-global-environment-in-stars-galaxy-cosmos-science-universe-exploration-of-atmosphere-astronomy-bfwfgnpzwke45tfyn
https://svs.gsfc.nasa.gov/11347
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https://www.istockphoto.com/photo/the-first-sunlight-of-planet-earth-gm174771982-22188869
This episode is sponsored by Wren, a website where you calculate your carbon footprint.

You can also sign up to make a monthly contribution to offset your carbon footprint or support rainforest protection projects. [♪ INTRO]. A little over a week ago, we got an important update from what is basically the definitive source on the climate crisis.

It came from the Intergovernmental Panel on Climate Change, or IPCC for short. The IPCC is part of the United Nations, and is made up of members from. UN countries and the World Meteorological Organization.

Their job is to assess the latest climate science and to provide information for governments that will help them make decisions about what they can do about the climate crisis. This latest report is from a group within the IPCC called Working Group 1, and that is the panel that looks at the physical science behind how the climate is changing. They’re the first of three teams of scientists to present their work.

Together, those three parts will form the IPCC’s sixth assessment report, due to be released in 2022. So what’s actually in there? Well, not a ton of good news.

According to the report, not only is the planet 1.09 degrees Celsius warmer, each of the past four decades has been warmer than every decade before it. And that is unequivocally because of human-made greenhouse gas emissions. Carbon dioxide levels in the atmosphere are higher now than they’ve been in more than 2 million years!

Sea levels are rising fast, and sea ice is the least it’s been since we started keeping records for it. The previous, fifth assessment report is now eight years old, so this update also summarizes what’s changed since that came out. For one, the science, which was already solid, has gotten even better.

Scientists have collected a lot more data over the years from many different sources, and from even more regions of the globe than ever before. So they understand the geochemical cycles of the atmosphere, oceans, and land much better. That means they can conclude with even more confidence that greenhouse gas emissions, and global warming, have led to the other symptoms of the climate crisis.

Stuff like increased rainfall, the melting of sea ice and glaciers, sea level rise, and ocean acidification all over the world in the last century. They’re also more confident than they were before that the climate crisis is behind recent extreme weather events, like more extreme heat waves and droughts. Plus, all the extra data researchers have collected over the years has fed into improving the climate models that form part of the report.

The models are now even better at showing what effect different levels of emissions might have on the earth’s temperature in the future. And brace yourself, because here’s the really bad news: some of that warming we’ve seen over the past century is locked in. Meaning that even if we got carbon dioxide emissions to net zero by 2050, and made cuts in other greenhouse gases, temperatures would keep rising up to 1.5 degrees warmer for the next half century before dropping off.

But there is an upside. What our climate future will look like really depends on what we do now. More greenhouse gases means more intense climate scenarios.

Less, and we have a chance of turning things around. If all countries met their promised emissions targets, we could keep warming to within 2.4 degrees of what it used to be pre-industrially. And there are already signs that what we’re doing is helping.

Because another study announced this week is great news for international efforts to protect the planet. The Montreal Protocol is the international agreement to protect the ozone layer by restricting the use of certain ozone-depleting chemicals. And it’s been really effective in that regard.

But according to a recent study in the journal Nature it’s had an additional knock-on effect in keeping carbon out of the atmosphere. In the study, researchers used chemistry climate models to track what could have happened if ozone-depleting chemicals weren’t restricted. Those models estimate that in a worst-case scenario where use of those chemicals kept growing, there could be a whopping 115 to 235 extra parts per million of CO2 in the atmosphere.

To put that in context, uh, that’s a lot. The authors calculate it’s around 30% more than what there would be otherwise. Put another way, that could have meant the planet would be an extra half to one degree warmer by the end of the century.

And since we are already over one degree, that... it’s just a lot. The researchers say that these effects were largely avoided because, by controlling the ozone-depleting substances in the atmosphere, we were helping land plants store carbon. See, the ozone layer normally blocks a specific type of ultraviolet radiation called UV-B.

That kind of radiation can damage plants, so that they can’t grow as tall and they grow fewer leaves. That decreases their ability to photosynthesize and suck up CO2 from the air. This study shows us that international cooperation can really work.

And it’s a lesson going forward. The new IPCC report says that if we get our emissions to very low or low levels now, then we could begin to see noticeable differences in global temperatures within 20 years. But we’re not there yet.

We really need to ramp up our efforts if we want to get on the path to not only securing a better climate, but a better world too. If you’re looking to do something about the climate crisis, you might like Wren. A website where you can calculate your carbon footprint, then offset it by funding projects that plant trees and protect rainforests.

Once you sign up to make a monthly contribution to offset your carbon footprint, you receive monthly updates from the projects you support. You get to see the trees you planted and what your money is spent on. We’ve partnered with Wren to plant 10 extra trees for the first 100 people who sign up using the referral link in the description.

Thank you again to Wren for sponsoring this episode, and thank you for watching. [♪ OUTRO].