Are we to blame?

How can we be sure that it is humans driving climate change?

It’s simple, look at all possible natural causes and weigh them against the evidence of the latest changes.
In other words, compare the possible and measurable effects of any given “natural” cause of climate change with the actual climate change. Then compare the effects of human activity on climate with the documented changes in climate change.

“Natural” cause here refers to anything other than the result of a human-driven activity.

So what are the possible natural causes for global climate change?
1.- Changes in solar output
2.- Explosive volcanic activity

These two have been carefully observed, and there is a general consensus among scientists that neither one of these is driving the current trends in climate change.

What has been driving it, is an increase in carbon dioxide release into the atmosphere.
Some may argue that there are natural events which result in increased release of CO2 into the atmosphere. While this is indeed true, the dramatic increase in CO2 output and consequent spike in atmospheric concentrations of the gas cannot be wholly accounted for by just looking at natural events.
When CO2 emissions into the atmosphere driven by human activity (= fossil fuel burning) are taken into consideration, it is clear that they are the primary source of the spike in CO2 concentration in the atmosphere.
The correlation between CO2 emissions and change in global temperatures is clear, and the bulk of the CO2 emissions can be traced back to human activity.

Here is a video interview with James Hansen, one of the first scientists to publicly warn of the effects of CO2 emissions on global climate change: