Let me answer your second question first. The amount of excess CO2 in the atmosphere is the driver for global warming.
Keep in mind that there is a lag between dumping CO2 into the atmosphere and warming, primarily because the ocean is a big CO2 reservoir. But the ocean releases CO2 as levels rise, and so CO2 cannot be trapped in the ocean indefinitely.
Your first question is mitigation, which is outside the scope of this topic. But, we never get real mitigation if people don't agree there's a problem.