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  • Let's talk about the science of climate change. Don't you mean Global Warming?

  • How'd you get in here? I'm the Internet, I never left. Now why'd

  • you change the name? Global warming wasn't happening so you had to call it "Climate Change"?

  • The overall average temperature of the planet is increasing so Global Warming is technically

  • correct, but that doesn't mean it's going to be warmer everywhere all the time.

  • And that leads to some confusion, like on a cold winter's day, you might say...

  • So much for global warming! Exactly.

  • So the term climate change indicates that the problem is more intense storms, droughts

  • and floods, ocean acidification, not just that the globe is warming.

  • But it's not. What?

  • The globe's not warming. Since when?

  • 1995 Um, that's not how you draw a trendline through

  • data. If the slope is nil, the climate's chill.

  • Y'know thirteen of the fourteen hottest years occurred this century and the graph you're

  • using is old, it doesn't include satellite data. If you take that into account, the trend

  • is obviously continuing upwards. Oh, so now you say it's warming. In the past

  • scientists told us it was cooling. Why can't they just admit that they have no idea what's

  • going on? It's true in the 1970's there were some papers

  • published predicting cooling, but over that same time period there were six times as many

  • papers predicting warming. So scientists really haven't changed their tune.

  • Well just judging by temperatures, I say they're wrong. The Earth is cooling.

  • But you don't just have to go by temperatures. There are plenty of other signs that the globe

  • is warming, like sea levels are rising three millimetres a year. That's an indication that

  • the oceans are getting warmer and so are expanding. Ice on Antarctica and Greenland is melting

  • at unprecedented rates and arctic sea ice continues to decline.

  • Nuh-uh. Arctic sea ice increased forty percent in the last two years.

  • That last little uptick? That's what you focus on? What about the general downward trend?

  • It could mean anything. You know if the Earth is warming the most likely source of the problem

  • is the sun. The sun is getting brighter. Did you ever think of that?

  • The sun was getting brighter, in the 1930's, and it probably contributed to some warming

  • then. But since the 50's the sun has been getting dimmer and temperatures continue to

  • rise. Oh, so you automatically assume it's man-made

  • CO2. You know humans only emit a tiny fraction

  • of the CO2 released into the atmosphere every year.

  • That's true. People emit about 30 gigatonnes compared with 780 gigatonnes from natural

  • land and ocean processes. So you admit it, humans aren't the problem.

  • No! Before us the system was in balance with the land and oceans absorbing that same amount

  • - 780 gigatonnes a year. This balance kept the carbon dioxide levels

  • in the atmosphere between 180 and 280 part per million for 800,000 years. Now it's at

  • 400 parts per million and still rising. But our small contribution couldn't have caused

  • that. Well the amount of CO2 in the atmosphere is

  • increasing by about fifteen gigatonnes or two parts per million every year.

  • But how do you know that's man-made CO2? Because the isotope carbon-13 is less common

  • in fossil fuels than it is naturally in the atmosphere. And over time we're seeing the

  • concentrations of carbon-13 are decreasing. But volcanoes emit way more CO2 than humans.

  • No they don't. They emit about 0.25 gigatonnes annually. That's less than one percent as

  • much as humans. OK, well even if we are responsible for the

  • rise in CO2, it doesn't matter because water is by far the most potent greenhouse gas.

  • Yes it is. I win.

  • No you don't! Water in the atmosphere is increasing as well.

  • But that can't be due to human activity. The only way for the atmosphere to hold more

  • water vapour is if it gets warmer. So... Hang on, you're not saying...

  • Yes! It all comes back to CO2. A doubling of CO2 on its own would increase the temperature

  • of the globe by one degree Celsius. But that warming means there will be more water vapour

  • in the atmosphere and ice will melt reducing the reflectivity of Earth's surface. So it's

  • a positive feedback loop, which a bunch of different sources of evidence all indicate

  • will lead to about a 3 degree Celsius rise in temperature.

  • But if this is true, why have all the predictions failed. In actuality most of the predictions

  • show remarkable agreement with observations. But you're probably thinking of the model

  • from 1988, back when we thought climate sensitivity was higher. If you re-run that model with

  • 3 degrees of warming for every doubling of CO2, the predictions match exactly the warming

  • that we've observed. But the Earth has warmed and cooled in the

  • past. So who was releasing CO2 then, aliens? We understand that past changes in the climate

  • were triggered at regular intervals by Milankovitch cycles, that is the periodic oscillation of

  • the Earth's tilt, precession of the tilt, and stretching and squishing of Earth's elliptical

  • orbit. During every warming cycle, CO2 and temperature

  • rise together. Ah, but if you look closely at that graph,

  • you'll see that CO2 lags behind the temperature rise, so it can't be causing the warming.

  • The CO2 doesn't cause the first warming. The Milankovitch cycles change the way the sunlight

  • hits the Earth and that causes a little bit of warming decreasing the solubility of CO2

  • in the oceans. So some of that CO2 is released and that is a positive feedback loop, which

  • amplifies the warming. In fact over 90% of the increase happens after the CO2 starts

  • to rise. Let's say you're right, and the CO2 we're

  • releasing is warming the planet. What's so bad about that? The planet gets a little warmer,

  • big deal. I'm not claiming it's going to be some sort

  • of crazy catastrophe, but we are going to get more intense storms, more droughts and

  • floods, the oceans will become more acidic, sea levels will rise and my point is it would

  • be better for all species on this planet and probably cheaper for us if we just started

  • reducing emissions now than if we wait and pay the consequences later.

  • No thanks. Why are you wearing sunglasses?

  • Global warming. This episode of Veritasium was supported by

  • Audible.com a leading provider of audiobooks with over 150,000 titles in all areas of literature

  • including fiction, non-fiction, and periodicals. This week I wanted to recommend the book Merchants

  • of Doubt, which is about scientists who have spread misinformation about certain topics

  • like how cigarettes cause lung cancer, or how CFC's cause the ozone hole, or now how

  • CO2 is causing the planet to warm. So if you want to find out more about that you can download

  • this book by going to audible.com/veritasium or you can pick any other book of your choosing

  • for a one month free trial. So I want to thank Audible for supporting me, and I want to thank

  • you for watching.

Let's talk about the science of climate change. Don't you mean Global Warming?

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關於全球變暖的13個誤解 (13 Misconceptions About Global Warming)

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    kwchu 發佈於 2021 年 01 月 14 日
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