Climate Change From Different Perspectives | PBS NewsHour
[William Collins, a senior scientist at the Lawrence Berkeley Laboratory and head of the climate science department] it's obvious the Earth's climate can change, and it can change for perfectly natural reasons. So we've been looking for fingerprints of man's influence on climate sort of in some sense, a smoking gun, that would prove that it's man that's causing the change. And we've actually found those fingerprints in the climate system. Some of them have to do with how the temperature of the surface and the atmosphere are changing together. It turns out that that's a very strong fingerprint of manmade climate change. You can't get that, that single that we're seeing from volcanoes. You can't get that signal from the sun. And those are two of the, really, the primary natural causes for climate change. The only way that we know of to get the atmosphere's temperature to change in the way that it's changed since the early 20th century is to add greenhouse gases. So that's a fairly strong hint. We also know from very good evidence that man is responsible for the increase in greenhouse gases. We can show that from basic laboratory chemistry. And that, that fact is really not in much dispute. So there's several signatures like the temperature that implicate man. You can't get climate to change in the way that it's changing, for example, if we have fewer volcanoes today than we had in the middle of the 20th century. Just not possible.
Abrupt climate change has become an important issue for us now. It's this joker in the deck that we discussed, where climate may respond quickly and change in a way that's almost irreversible. So for example, if a major piece of Antarctica were to break off, we would regard that as a form of abrupt climate change. And once the ice breaks off of Antarctica, it will contribute to sea level rise. The melting of glaciers on land, it's a slower process. That's a form of irreversible climate change. At least in our lifetimes. Once those glaciers go away we won't see them come back for thousands of years. So we're increasingly concerned about changes in the climate system where large parts of the Earth may change. All at once. Quite quickly. And we may not see it coming until it happens.