When it comes to hurricanes how is it that humans can cause them.... or even effect their strength?

Strangely, the number and intensity of Atlantic hurricanes has not increased. This is one of the predictions of Global Warming that has not panned out and the name changed to Climate Change. It has NOT worked the way the models said it would.

In hurricane season 2004 - 2005, 5 hurricanes hit Florida and that event was absolute proof that Global Warming was causing more hurricanes and, with Hurricane Andrew and Hurricane Katrina, more intense hurricanes. But, it has been very quiet ever since with few hurricanes and not very intense hurricanes.

BTW: The hurricane of 1849 that hit Tampa, Florida was at least as intense as Hurricane Andrew or Hurricane Katrina.

Over the course of the past 800,000 years, says NOAA, CO2 levels bounced between 180 and 280 parts per million. Ever since the industrial Revolution CO2, one of the major greenhouse gases has increased by over 36% significantly altering global climate. This is just one of the ways humans affect the earth. With this increase in greenhouse gases we impact how much energy (heat) is absorbed from the sun by the earth, our power plants don't power hurricanes directly, but indirectly the definitely do.

Hurricanes are essentially giant heat engines. Global warming, spurred by increases in atmospheric carbon dioxide has increased global temperatures. More heat means more chances for hurricanes.