It's a Gas!
Test your knowledge of carbon dioxide and why it's so important to climate stability and our quality of life.
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From 1751-2003, humans added 466 billion tons of carbon to the atmosphere in the form of carbon dioxide. Eighty-five percent of all human-produced carbon dioxide comes from burning coal, natural gas, oil and gasoline.
Forest clearing produces about a fifth of current carbon dioxide emissions. Interestingly, cows, which produce massive amounts of methane (also a potent greenhouse gas), are becoming a cause for concern in countries with large cattle industries.
Forty to 50 percent of the carbon dioxide stays in the air, and 30 percent is dissolved in the oceans. Scientists are not sure about the rest. They believe it is absorbed by forests, soil and crops.
Water vapor actually has more heat-trapping power than carbon dioxide. It is also more abundant. But carbon dioxide and water vapor interact in crucial ways — more carbon dioxide means the atmosphere gets warmer, which creates more water vapor, which then traps heat and warms the atmosphere even more.
The amount of carbon in the oceans, land and air is naturally very finely tuned, but human activity is upsetting that balance, with effects all over the globe. NASA's Soil Moisture Active Passive (SMAP) mission, to be launched in 2014, will use soil moisture measurements to improve our understanding of the water, energy and carbon cycles.
Half of this 20-ton so-called "carbon footprint" comes from transportation (cars, trucks, buses, aircraft). In contrast, the average European produces about 14 tons per year, and the average Indian about one ton per year. For a sustainable life, each person on the planet should produce no more than two tons of carbon dioxide per year.
Both Venus and Mars have atmospheres made of about 96 percent carbon dioxide. Earth's atmosphere started out like Venus' atmosphere. But Earth's ocean absorbed much of this carbon dioxide and, as photosynthesis evolved, plants converted carbon dioxide to oxygen, increasing oxygen levels in the air from 0.01 percent to 22 percent today.
Shutting down fossil fuel plants and moving to clean, renewable energy sources (e.g., the sun and wind) would have the biggest impact. Coal-based plants are the least carbon-efficient power stations.
The uptake of carbon dioxide by forests and plants varies with the seasons. Most vegetation is in the northern hemisphere, where most land is located. In the northern spring, new plant growth uses more carbon dioxide. In the northern fall, plants and leaves die and release the gas back into the atmosphere.
Even if we stopped all carbon emissions right now, the hundreds of billions of tons of carbon dioxide that have been pumped into the atmosphere and absorbed by the oceans since the Industrial Revolution would continue to warm the planet. For how long? No one knows for sure, but estimates range from hundreds of years to thousands of years into the future.