Humans are playing an important role in climate change. Some activities caused by humans are the root problems. the greenhouse gas (GHG) emissions that human activity generates—are the leading cause of the earth’s rapidly changing climate today. 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 U.S. Environmental Protection Agency, our current concentrations of carbon dioxide, methane, and nitrous oxide “are unprecedented compared with the past 800,000 years.” Indeed, the atmosphere’s share of carbon dioxide—the planet’s chief climate change contributor—has risen by 46 percent since preindustrial times.
The burning of fossil fuels like coal, oil, and gas for electricity, heat, and transportation is the primary source of human-generated emissions. A second major source is deforestation, which releases sequestered (or stored) carbon into the air. It’s estimated that logging, clearcutting, fires, and other forms of forest degradation release an average of 8.1 billion metric tons of carbon dioxide per year, accounting for more than 20 percent of all global CO2 emissions. Other human activities that generate air pollution include fertilizer use (a primary source of nitrous oxide emissions), livestock production (cattle, buffalo, sheep, and goats are major methane emitters), and certain industrial processes that release fluorinated gases. Activities like agriculture and road construction can also change the reflectivity of the earth’s surface, leading to local warming or cooling.
Though our planet’s forests and oceans absorb greenhouse gases from the atmosphere through photosynthesis and other processes, these natural carbon sinks can’t keep up with our rising emissions. The resulting buildup of greenhouse gases is causing alarmingly fast warming worldwide. It’s estimated that the earth’s average temperature rose by about 1 degree Fahrenheit during the 20th century. If that doesn’t sound like much, consider this: When the last ice age ended and the northeastern United States was covered by more than 3,000 feet of ice, average temperatures were just 5 to 9 degrees cooler than they are now.