Volcanic eruptions since 2000 have caused a temporary cooling that cancels out part of the heating effect of greenhouse gases.

To cancel it out entirely would require a higher level of vulcanism. However, that would work only for a time. As we pump more greenhouse gases into the atmosphere, cancelling them out would require a steadily increasing level of vulcanism.

Setting aside the harm those eruptions would do if they occurred, there is no reason to expect them to happen.

Moreover, eruptions can also emit greenhouse gases, so over the long term they can make things worse.