When evaluating the historic contributions made by different countries to the greenhouse gasses found in Earth’s atmosphere, calculations generally go back no further than the year 1840 which is roughly when the industrial revolution began. But this may not be fair since civilization has been around far longer than that. New research from Carnegie’s Julia Pongratz and Ken Caldeira shows that carbon dioxide contributions from the pre-industrial era have an impact on our climate today. Their work is published in Environmental Research Letters. The burning of fossil fuels that came with industrialization released massive amounts of carbon dioxide emissions into the atmosphere, which has helped cause global warming. But clearing forests and other wild areas for agricultural purposes also contributed to atmospheric carbon dioxide, and that has been happening since before industrialization.