There are very obvious features we've observed that indicate in the last 20 years the climate has been changing. Just looking at the changes in the glaciers in 20 years, the glaciers on the coastlines have been reduced in volumes.
One of my students in 2002 was on a cruise to the Antarctic, and in January they collected samples along the Larsen B ice shelf. In late February or early March of that same year ... that ice shelf just totally collapsed. The significance was that ice shelf had been there for the past 10,000 years.
We're at a point now where it is hard to predict what is going to happen. We've seen situations that were maybe similar in the past but that is all interpretive we haven't lived it.