Dr Richard Muller doubted the reality of climate change. So he started a new research body to go back to the basic data and recalculate global temperatures from scratch. Here's an interview with him where he discusses his findings.
And here's the chart showing the 10 year average of average land global temperatures compared with a simple regression fit based on CO2 levels and volcanic activity. Note: this is not the temperature anomaly relative to some average base period--it's actual temperatures.
Muller's model has carbon dioxide driving a strong upward trend and sulphate emissions from vulcanism causing short-lived downward spikes. Sulphate emissions from volcanic eruptions temporarily cool the atmosphere. As Dr Muller says, it's a very good fit.
Dr Muller was the darling of the Right until he said that global warming was real and caused by man, and even received funding from the Koch brothers. In the end, his analysis produced a similar pattern to what other groups had calculated, while calculating a longer record allowed his group to show more precisely the negative effect of sulphate emissions.
I suppose we could simulate volcanic eruptions by pumping sulphur dioxide into the stratosphere if temperatures keep on rising. But I have no idea how much that would cost, or whether the cure would be worse than the disease. We stopped emitting sulphates from our industrial chimney stacks because of acid rain. Matters would have to be dire indeed to go back to that.