Depending on who you ask, you get a different figure.
Some argue that its zero to negligible, whilst others argue that it's a lot higher, whilst a few argue that humans are solely responsible.
I personally believe it's somewhere between negligible to lower contribution.
I do not believe that we should now start tampering with the climate. Every few years, we release a new paper saying how we understand the climate works, which just goes to show that we don't know it all yet, and ramming proverbial knives into the climate toaster is probably not the best way to get the crumpet out