There are three reasons I believe in human caused global warming. First, I have noticed hotter summers and milder winters. It has been several years since there has been any snow where I live. More days in summer have temperatures above 90 Fahrenheit.
Second, I believe that on any complex and controversial issues the consensus of the experts is more likely to be true than mistaken.
Third, I understand the science. During the age of dinosaurs the climate on earth was much warmer. Sea levels were higher. Much of what is now the United States was under water. Tropical plants lived closer to the North Pole and the South Pole than now.
Over a period of many millions of years plants removed carton from the atmosphere using photosynthesis. This carbon was deposited as coal, petroleum, and natural gas. As the percentage of carbon dioxide in the atmosphere declined, the climate cooled.
By consuming fossil fuels we are reversing a process that lasted for several hundred million years in several hundred years. This is the reason why the summers get hotter, and why the winters get milder.