What released an estimated 8.7 million tons of the global warming gas?

California’s wildfires sent millions of tons of carbon dioxide into the atmosphere. University of Colorado researchers report that from October 19th to the 26th, an estimated 8.7 million tons of the global warming gas were released. Armed with that report, a key U.S. House committee on energy and warming sought answers from a panel of scientists.
Question: What released an estimated 8.7 million tons of the global warming gas?