Greenhouse gases trap heat in the atmosphere and keep Earth warm. Without them it would be a frozen iceball – as it once was before.

There are many greenhouse gases. Water vapor is by far the largest by volume, and does most of the warming.

Carbon dioxide is the weakest greenhouse gas in warming potential, but the second most abundant.

Carbon is always moving between Earth and sky in what’s called the carbon cycle.

But since humans have industrialized, we’re transferring carbon that was held in fossil fuels into the atmosphere, where it lasts about a century.

We measure the warming impact of other gases in CO2 equivalent.

Methane, for instance, is 80 times more potent than CO2, but lasts in the atmosphere only a few decades.

It’s naturally produced by decaying plants in swamps, lakebeds, and forest floors. And by human sources like natural gas leaks and livestock.

Nitrous oxides also occur naturally, emitted from soils beneath wild plants and oceans. And through our agriculture, by using nitrogen-based fertilizers.

These are 300 times more potent than CO2, though produced in much smaller quantities.

Fluorinated gases are manmade, and emitted only from human sources, like leaking refrigerant.

The volume is tiny, but they’re thousands of times more potent than CO2, and endure for thousands of years.

Only by understanding the mix and potency of greenhouse gases can we understand how to best manage them.