When a large asteroid hit the earth, sixty-five million years ago, it kicked up a huge amount of dust. The dust dimmed the sun for so long that the surface of the earth cooled sufficiently to wipe out the dinosaurs (incidentally giving mammals a chance to develop into the rich variety we see today).
If such a threat were in our near future, CNN and all the other news channels would be screaming about it. There would be non-stop coverage, on what we could do to avert the disaster, and how to cope should it strike anyway, and how each of us would be affected. You couldn't get away from this news.
A similar threat is actually upon us, but going the other way: the earth is steadily warming. If we keep burning fossil fuels at today's rate, the average global temperature may rise by 4 degrees C by 2100. That doesn't sound like much, but the last time the world was 4C cooler on average, we were in an ice age, and life looked very different from the way it is today.
Global Warming from 1880 to 2013.
And it will keep warming past the year 2100. We don't know what life will look like when it's more than 4C warmer: it hasn't been that warm for millions of years.
This is an astonishing thought: the planet, our home, would be altogether a different place from what it is today. And while the changes appear slow on a human time scale, the warming is occurring at an unprecedented rate. Already species are feeling the pressure, and it is not clear how many will survive the changes that are very rapid on an evolutionary time scale. It's clear: we must do what we can to keep the warming below 2C.
You would think that would make the news.








