Let me state from the outset: I’m not about to tell you ongoing warming was the cause of the catostrophic flooding in South Carolina. It is nearly impossible to conclusively tie any one extreme weather event to human activity-caused warming, which is continuing in the oceans and again is accelerating in the atmosphere. We all know weather extremes occurred at irregular intervals before anthropogenic warming accelerated with increased burning of fossil fuels. There is natural variability in the background of the earth’s climate which has played a role in many extremes in the past. But CO2 is an indisputable greenhouse gas, and climate models show when run with CO2 levels which were in place around 1900, there would have been no global warming. With natural warming/forcing elements taken to the max (solar, volcanic emissions, etc) there is no other explanation for the warming which has been occurring. These models show, in fact, some modest cooling would have been occurring most of the 20th and the early 21st centuries without all the extra CO2 we’ve pumped into the atmosphere. CO2 levels are now higher than they’ve been in at least 850,000 years.
As the atmosphere warms, it can hold more water vapor. And as the seas warm, there is more evaporation adding more water vapor to the air. What is most alarming to climate scientists is the clear increase in the number of heavy to extreme precipitation events in recent decades, which is precisely what 14 climate models had predicted years ago. It makes well explained sense in terms of the laws of physics. So while neither I nor other scientists can prove that this latest disaster has a direct link to global warming, there is good evidence we will continue to see more extreme precipitation events more often.