Carbon emissions refer to any human activity that contributes to the accumulation of carbon dioxide in Earth’s atmosphere. Carbon dioxide acts as a greenhouse gas, trapping solar infrared radiation and amplifying the natural warming effects of sunlight. Each ton of CO2 added to the atmosphere warms the planet by about 1.5 degrees Fahrenheit.
The most important source of emissions is energy-related: burning fossil fuels like gasoline, diesel, and coal for heat, light, and power. The combustion of these fuels produces carbon-dioxide and other pollutants, such as methane and nitrous oxide. The extraction, processing, and transport of fossil fuels also contributes to emissions.
Emissions from buildings, commercial and residential, industrial, and agricultural activities account for another significant share of global emissions. This includes electricity generation, cooking, heating, and cooling, as well as soil erosion and land-use change.
Air transportation is another major contributor to greenhouse gases. This includes road vehicles powered by petroleum-based fuels, such as gasoline and diesel, as well as ships and planes. This sector accounts for about 14 percent of global energy-related carbon-dioxide emissions.
In recent years, human-driven CO2 emissions have been increasing quickly. While they have occasionally slowed or even dipped (such as during the pandemic when travel and manufacturing slowed dramatically), they continue to rise from year to year, and at an ever-faster rate.
The atmospheric concentration of carbon dioxide has increased from about 280 parts per million (ppm) at the end of the last ice age to its current value of 422.8 ppm—a 100-fold faster rate than the average increase between ice ages. The chart below shows a timeline of the rise in atmospheric CO2 over the past several centuries, based on air bubbles trapped in mile-thick ice cores.
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