The science behind climate change isn’t hard: Burn carbon-based fuels (virtually all fossil fuels are carbon-based) and you add heat-trapping carbon to the atmosphere. Create oxygen-free conditions for decomposition, such as those in the still water behind a dam or in a landfill, and methane results.
Since pre-industrial times, the concentration of CO2 in our atmosphere has risen by about a third, from 280 parts per million (ppm) to 378 ppm. Methane has doubled its concentration from .78 ppm to 1.76 ppm. CO2 and methane levels haven’t been this high since the age of the dinosaurs. Current methane levels are the highest they’ve been in 420,000 years. The current concentration of CO2 is the highest it’s been in 20 million years.