In the modern age, the Anthropocene, global biogeochemical cycles are skewed by the massed action of almost 7 billion human beings. Chief among these forcings is the burning of both fossil and modern biomass. The burning of crops and forest by humans can be viewed on a global scale with imagery from NASA's Earth Observatory. Some of the fires viewed by NASA's satellites are due to natural causes, some are due to human causes, and many are a combination of human land use practices and natural causes.
Fires in the Amazon have increased to 2007. The good news is that since then the fires seem to have decreased, possibly as a result of lowered Soy and Beef prices.
A number of sources have recently discussed melting glaciers in the Himalayas, probably due to a combination of global temperature increase and soot (carbon particulate) from burning.
Africa has some of the most pronounced anthropogenic burning, although it is debatable whether much of the semi-arid regions would burn naturally. Interestingly, the Sahel is also reported to be "greening" since the droughts of the 1970's. I was first alerted to changes taking place in the Sahel by a short article from the University of Arizona School of Natural Resources. Now, I read in The Nation, an article by Mark Hertsgaard about farmers in Burkina Faso who have let trees grow in their fields (because of changes in government regulations that let them own trees on their land) to increase the productivity of their crops. However, after reading this, and other, sources, I'm still having trouble understanding farming practices in the region, specifically in regards to reconciling the massive burning evident from MODIS with the greening described in the articles.
Australia has also recently been afflicted by catastrophic wildfires caused by a combination of extreme drought and heat waves.
Soot is near the upper right corner of this diagram from C.A. Masiello, “New directions in black carbon organic geochemistry,” Marine Chemistry 92, no. 1-4 (December 1, 2004): 201-213.
Ironically, pyrolysis, or the incomplete combustion of biomass to create charcoal or biochar, is now touted as a possible technology to increase crop productivity by simultaneously sequestering carbon. Not as currently practiced, though.