Cutting down trees can cause cooling, not warming as has been thought:
A paper in tomorrow's issue of Nature says cutting down trees north of 45 degrees latitude has a net cooling effect.
Trees sequester carbon, so cutting them down releases that carbon back into the atmosphere. But this study finds that the open area thus created is cooler, because it reflects more heat back into space, especially when there is snow on the ground.
Most temperature stations are in open grassy areas, so using them might lead to a slight underestimate of average global temperature.
On the other hand, climate models might be slightly overestimating future warming.
I have some questions into the researchers to try to sort these numbers out.