To the Editor:
Interviewed on PBS's NewsHour, David Wallace-Wells, author of "The Uninhabitable Earth: Life After Warming," stated: “Most scientists talked about two degrees as the sort of threshold of catastrophe.”
William Brangham: Two degrees Celsius.
Wallace-Wells: Yes. And that's about twice as much warming as we have had today. They describe that threshold as the threshold of catastrophe. We're on track to get to about 4 or 4.3 degrees Celsius by the end of the century.
And that whole range is really unconscionable in terms of how much climate suffering it would impose. And we have only just begun to see peaks of it, with wildfire and extreme weather.
Brangham: People hear two degrees, three degrees, four degrees, and those distinctions might seem trivial to people who are not immersed in this.
Wallace-Wells: Four degrees of warming, we would have, the UN suggests, as many as a billion climate refugees. That's as many people as live in North and South America combined. We would have $600 trillion of climate damages. That's double all the wealth that exists in the world today. And the impacts would be everywhere, not just on the sea level, not just on Arctic melt, not just on heat waves and droughts, but there would be no life on Earth that would be untouched by these forces. That's how all-encompassing the climate system is.
To put this into personal perspective, consider that a human body has, on average, a normal body temperature of between 97.7–99.5 F (or 36.5–37.5 C). If your body’s temperature were to increase by just one degree Celsius from say 37 C (98.6 F) to 38 C (100.4 F) you would have a fever and feel unwell. Increasing by 2 C to 39 C, which is 102.2 F, then you are ill. Increasing by 3 C (or 104 F), now you’re very sick. By 4 C (or 105.8 F) indicates someone burning up with fever attempting to fight off serious infection. Another degree Celsius would likely be fatal. Think of planet Earth’s average temperature similarly, warming through climate change toward a fatal fever.
Patrick Ivers, Laramie