Scientists say droughts and wet periods come and go between ice ages. To understand and predict long-term climate changes, Northern Arizona University assistant research professor Nick McKay examines sediment samples from Arctic lakes.
McKay says, "we lower a big PVC tube into the bottom of the lake and pound it into the bottom and pull it up full of mud". He says, "we ship that back here to Flagstaff and analyze it for a whole variety of different things that can tell us different stuff."
McKay's Arctic research shows the climate has been changing faster in the last 100 years than it naturally has in the past. He says it's also changing in the opposite direction of what scientists would project. "If you look at the long-term trend, it would suggest that the 20th century would have continued to get cooler, or at least stayed about the same as the 19th or 18th centuries. Instead, it's become much warmer. In fact, it really stands out as an outlier. McKay goes on to say, "some of the results from a lot of our work in the Arctic is that over the past 2,000 years, going back further over the past 6 to 8,000 years, we've been on a general cooling trend. That's what se see throughout the Arctic. it's been getting consistently and steadily cooler over the past several thousand years, and this is exactly what we would expect."
The most dramatic evidence of climate change McKay has witnessed is the melt back of glaciers in Alaska. He says they've become significantly smaller since the 1970's. This warming trend, McKay says, can only be explained by the presence of greenhouse gases in the atmosphere.