Believe it or not, very little research has ever been funded to search for natural mechanisms of warming... it has simply been assumed that global warming is manmade. Climate change - it happens, with or without our help.
Contrary to popular accounts, very few scientists in the world - possibly none - have a sufficiently thorough, "big picture" understanding of the climate system to be relied upon for a prediction of the magnitude of global warming. To the public, we all might seem like experts, but the vast majority of us work on only a small portion of the problem.