> >As we all know, the earth has gone through warm and cool phases in the past, and long before humans were around. Forces that contribute to climate change include the sun’s intensity, volcanic eruptions, and changes in naturally occurring greenhouse gas concentrations. But records indicate that today’s climatic warming—particularly the warming since the mid-20th century—is occurring much faster than ever before and can’t be explained by natural causes alone. According to NASA, “These natural causes are still in play today, but their influence is too small or they occur too slowly to explain the rapid warming seen in recent decades.”
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> >Humans—more specifically, the greenhouse gas (GHG) emissions we generate—are the leading cause of the earth’s rapidly changing climate. Greenhouse gases play an important role in keeping the planet warm enough to inhabit. But the amount of these gases in our atmosphere has skyrocketed in recent decades. According to the Intergovernmental Panel on Climate Change (IPCC), concentrations of carbon dioxide, methane, and nitrous oxides “have increased to levels unprecedented in at least the last 800,000 years.” Indeed, the atmosphere’s share of carbon dioxide—the planet’s chief climate change contributor—has risen by 40 percent since preindustrial times.
