Anthropogenic climate change is climate change caused by humans. This has been the main driving force for climate change as a whole since industrial times. But how do we know that this is true? How do we know that the change in climate is mainly anthropogenic?

Since 1950, the CO2 levels(parts per million) have reached levels that they haven't been at for at least 800,000 years.

The sun can not be behind the warming of the globe. A altitude-heat graph would show that the troposphere generally gets cooler as you increase in altitude. This happens because the light emitted by the sun is of short wave length, which most of the atmosphere does not absorb. But when it hits the ground, it gets absorbed and remitted as longer wave lengths. This gets absorbed by the atmosphere. Now, as you increases in altitude more and more of this heat is absorbed and less of it passes through the atmosphere. But once you cross over into the stratosphere this stops, and now the temperature increases with altitude. This is because of the ozone layer. The ozone layer does absorbs some amount of the shortwave length sun light, and remits this upwards. This results in the rest of the stratosphere increasing in temperature.

Now, over the last 150 years, the troposphere has been increasing in temperature. But at the same time the temperature of the stratosphere has been decreasing. There are two plausible explanations for this: one, there is more sun light or two, there is a build up of CO2(and other greenhouse gases). Hypothesis one can not be true, as it would result in the whole atmosphere heating up. Hypothesis two, on the other hand, is true because it results in in the stratosphere cooling down while the troposphere heats up. Hence, global warming is caused by the build up of CO2 and other greenhouse gases, not an increase in sunlight.