Climate change skeptics like to say that the only evidence we have to support claims of human-caused climate change lies in (faulty) computer models.
In fact the evidence is a cascade of findings from different sources of which computer models are only one piece, all of which seems to agree.
I was reminded of this today when I read an article in the journal “Science” that described a multi-year effort by a team of researchers to drill out a core sample from the sediment below a tiny Russian lake 100 km north of the Arctic circle. The unpronounceable Lake El’gygytgyn is unique because it was never covered by glaciers, so the sediment below lake bottom is an accurate record of what was deposited on the lake stretching back to 3.6 million years ago.
This takes us back to the mid-Pliocene, when concentrations of carbon dioxide in the atmosphere were between 380 and 450 parts per million. By comparison, last month the world celebrated the dubious achievement of topping 400, and rising.
What the researchers found, among other things, was evidence of a completely ice-free Arctic, with pollen deposits from five different kinds of pine trees and other warm and wet-loving plants.
Bottom line: we probably won’t be seeing arctic forests and massive sea-level rise in our lifetimes – the Arctic is a big chunk of ice that will take a long time to melt – but we seem to be on the road to get there. That message comes to us not from a computer model of global climate, but courtesy of a very old hunk of Russian dirt.