Between 1997 and 2018, the Koch brothers gave over $145 million to climate-change-denying think tanks and advocacy groups including the Heartland Institute, Americans for Prosperity, and the Cato Institute. A Drexel University study found the majority of climate denial funding was 'dark money' using organizations with 'ambiguous names' to 'obscure the true agenda.' Koch Industries was the number one producer of toxic waste in the US by 2012 and paid a $35 million penalty for 300 oil spills. When Koch-funded academics accepted climate science, the brothers dropped them.