Earth at 2° hotter will be horrific. Now here’s what 4° will look like.
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The best-case scenario of climate change is that world gets just 2°C hotter, which scientists call the "threshold of catastrophe".

Why is that the good news? Because if humans don't change course now, the planet is on a trajectory to reach 4°C at the end of this century, which would bring $600 trillion in global climate damages, double the warfare, and a refugee crisis 100x worse than the Syrian exodus.

David Wallace-Wells explains what would happen at an 8°C and even 13°C increase. These predictions are horrifying, but should not scare us into complacency. "It should make us focus on them more intently," he says.
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DAVID WALLACE-WELLS:

David Wallace-Wells is a national fellow at the New America foundation and a columnist and deputy editor at New York magazine. He was previously the deputy editor of The Paris Review. He lives in New York City.
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TRANSCRIPT:

DAVID WALLACE-WELLS: Well, I think when we look outside our windows every day, we see a world that is basically stable, and even if we hear a lot about extreme weather, see horrible news of wildfires and droughts and heat waves that kill people all around the world, we still reorient our emotional expectations for what the world will be like in our own lives. And most of our lives have not been yet all that dramatically disturbed by climate change. But in the decades ahead, I think they will be. There's basically no life on Earth that will be untouched by the force of climate in the decades ahead, and in most cases, that means deformed, damaged, transformed.

I think most scientists would say that the best case scenario is 1.5 degrees Celsius of warming. But personally, I think it'll be practically impossible for us to stay below two degrees without what's called negative emissions technology, which is fanciful tech that has been tested and is successful at a lab scale, but needs to be deployed at global scale to make much of a difference. The UN says that to have any chance of staying below two degrees, we need massive use of this technology, which we don't even know enough to trust. So for me, I orient my best case scenario at two degrees. And unfortunately, that's a level of warming that most scientists describe as the threshold of a catastrophe. Many island nations of the world describe it as genocide. That's how vulnerable they are to especially sea level rise at two degrees. But the impacts wouldn't just affect the island nations of the world. Many of the biggest cities in South Asia and the Middle East would be lethally hot in summer at two degrees, which could happen as soon as 2050. These are cities like Calcutta 5, 10, 12 million people. You wouldn't be able to go outside or certainly work outside without incurring a lethal risk. And that could happen, again, just by 2050, which is one reason why the UN expects that we could have 200 million climate refugees by that same date, 2050. 200 million. They think it's possible that we get as many as one billion, which is as many people as live today in North and South America, combined. I don't think those numbers are realistic. I think they're too high. But even if we get 100 million or 150 million climate refugees, it's important to remember that the Syrian refugee crisis, which totally destabilized European politics, led in its way to Brexit, and has transformed our politics globally through the way it's affected Europe, was the result of just one million Syrian refugees coming to the continent. We're talking about a refugee crisis that is almost certain to be 100 times as large, and it comes at a time when most nations of the world are retreating from our commitments to one another, retreating from our organizations and alliances, retreating from the UN, retreating from the EU, and embracing xenophobia and nativism and nationalism. That's especially concerning when you think about what's ahead, because there are going to be many more people in much more desperate need in the decades ahead. And if we don't welcome them, we'll be committing real moral crimes that from the advantage of today seem unconscionable, but which may become more normal, as we move forward into this new transformed world.

When we talk about worst case scenarios, there are a couple of different factors at play. One is what humans do. This is the most important factor...

Read the full transcript at https://bigthink.com/videos/climate-c...