Is climate change natural or human-made?
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Both natural and human factors can lead to climate change.
Even if people were burning no fossil fuels, we might be seeing gradual shifts in Earth’s climate – including warming or cooling. The main natural process that has led to climate change over the last million years – the ebb and flow of ice ages – is a set of cyclic variations in Earth’s orbit around the Sun that have been mapped out for many years.
However, there is no scientifically demonstrated explanation for the warming trend of the last few decades other than human-produced greenhouse gases (see Figure 1). There is also no sign of a large natural shift in climate that might be greatly exacerbating or weakening the changes related to human activity.
The existence of large climate changes in the past is no source of comfort. The fact that lightning bolts have produced forest fires for millennia doesn’t mean that cigarettes can’t cause forest fires today. Similarly, it’s true that variations in Earth’s orbit, global volcanism, and other factors have produced massive climate change in the past. But this doesn’t prohibit humans from having our own impact on climate.
