The point is that if you convert a white landscape to a boreal forest, the surface suddenly starts collecting a lot more solar energy. That trend is occurring now, as seen in these two photos from a recent ScienceNews article, "Boreal forests shift north."

"Upper photo taken in 1962 shows tundra-dominated mountain slope in Siberian Urals. A 2004 photo of the same site, below, shows conifers were setting up dense stand of forest."

Now, another major study warns that the warming-driven northward march of vegetation poses yet another threat to the tundra.

The study, "Frequent Fires in Ancient Shrub Tundra: Implications of Paleorecords for Arctic Environmental Change," finds:

... greater fire activity will likely accompany temperature-related increases in shrub-dominated tundra predicted for the 21st century and beyond. Increased tundra burning will have broad impacts on physical and biological systems as well as on land-atmosphere interactions in the Arctic, including the potential to release stored organic carbon to the atmosphere.

The concern is not so much the direct emissions from burning tundra. As the article concludes:

... studies of modern tundra fires suggest the possibility for both short- and long-term impacts from increased summer soil temperatures and moisture levels from altered surface albedo and roughness, and the release soil carbon through increased permafrost thaw depths and the consumption of the organic layer.

Click on the image above to see just how much the fire changes the albedo of the tundra landscape.

We must get serious about reducing greenhouse-gas emissions now, since the consequences of hitting 1,000 ppm are simply too dire to risk.

This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.