A NASA-led study found that the extreme wildfires in Canada during 2023 released approximately 640 million metric tons of carbon from May to September, surpassing the annual fossil fuel emissions of large nations like Russia and Japan. This amount is comparable to the emissions of a major industrialized nation and only exceeded by the United States, China, and India. These findings, published in the journal Nature, raise concerns about the reliability of forests as carbon sinks, as climate change leads to more frequent and intense wildfires. While the carbon from wildfires can eventually be reabsorbed by regrowth, this is not the case for fossil fuel emissions. The study used satellite data and advanced computing to estimate these emissions, highlighting the urgent need to reassess global carbon budgets and climate targets in light of changing fire regimes.