I think the area burned in the North American boreal forest is controlled by the frequency of mid-tropospheric blocking highs that cause rapid fuel drying. Climate controls the area burned through changing the dynamics of large-scale teleconnection patterns (Pacific Decadal Oscillation/El Niño Southern Oscillation and Arctic Oscillation, PDO/ENSO and AO) that control the frequency of blocking highs over the continent at different time scales. Changes in these teleconnections may be caused by the current global warming. But,in fact, most studies on fire frequency in the boreal forest of North America show that, despite significant increases in temperature since the end of the Little Ice Age, the frequency of fires decreased in the last 150 years. Why prolonged and severe droughts were common in the past and were partly associated with changes in the PDO/ENSO system? Sofia