The amount of oil burned each day would cover 20 square miles to a depth of a foot. In a year, that's 20 square mile to a depth of 365 feet. It's a lot of carbon.
The amount of carbon dioxide in the atmosphere has been measured at the top of Mauna Kea in Hawaii for many years. The upward trend of CO2 is undeniable.
The upward trend of global temperature is harder to measure, but the best measurements are consistent with a rise due to the increase in CO2.
All that is science. What is not science are the various projections of ecological, economic, and social harm of various types in the future. This is what used to be known as "futurism", and it has a scientific component but it is also based on modeling, economics, etc. that include many assumptions and estimates.
I can't see that a warming of 3 degrees C would be such a big problem. It corresponds to a shift of about a half of a hardiness zone.
