CO2 was supposed to lead to increased storms around the equator. Never happened. After Katrina, we were supposed to live with increased storms. Never happened. This summer, the UK is having cold, wet weather. Never reported. When we had a cold spell recently, many leftist sheeple told me "weather is not climate." Now it is. How convenient.
But the number one reason to doubt that man is causing global warming: People with the facts on their side don't fake the data, nor do they personally attack those with another viewpoint.