The new study, published Wednesday in the journal Nature, found that 213 heat waves were substantially more likely and intense because of the activity of major fossil fuel producers, also called carbon majors. They include oil, coal and cement companies, as well as some countries. The scientists found as much as a quarter of the heat waves would be “virtually impossible” without the climate pollution from major fossil fuel producers. Some individual fossil fuel companies, such as ExxonMobil, Chevron and BP, had emissions high enough to cause some of the more extreme heat waves, the research found.