Earth has many processes that regulate carbon, atmospheric carbon dioxide, and its role in the carbon cycle and climate. How much do you know?



Fires release the carbon stored in plants, so measuring the extent and severity of forest fires around the globe is an important ingredient in understanding the carbon cycle.

Using NASA satellites such as Landsat, people can study the severity, size and location of forest fires from space, and we can estimate how much carbon is released into the atmosphere as the fires burn.


Which one of these increases the level of carbon dioxide in our atmosphere?

Every time we drive a car, take a flight, burn fossil fuels for energy, or cut down trees or clear land of vegetation, we add carbon dioxide into the atmosphere.


Why do levels of carbon dioxide in the atmosphere fall during the summer in the Northern Hemisphere?

In contrast to the Northern Hemisphere, the Southern Hemisphere is covered by more ocean than vegetation.


Plants use carbon dioxide and water to make their own food through the process of photosynthesis. When they are performing photosynthesis, plants reflect light strongly in which of the following wavelengths?

Plants such as trees, grasses and crops that are photosynthesizing reflect strongly in infrared light (light with wavelengths longer than those of visible light). We cannot see infrared light, but instruments on satellites like the Landsat satellite can. By precisely measuring the amount of infrared light reflected by plants, we can get a handle on the health of that vegetation.


Plants on land have taken in approximately half of the carbon dioxide that humans have put into the atmosphere over the last several decades.

Plants have taken up about a quarter, not half, of the carbon dioxide we've pumped into our air over the last several decades. When plants have enough water and nitrogen, they tend to grow more if there is a lot of carbon dioxide in the air. As we add more carbon dioxide to the air (through burning of fossil fuels, cutting down trees and so on), the possible additional growth by vegetation may help counter some of our impacts. However, we may not be able to count on plants to continue to take up extra carbon dioxide, because plants have limits to the amount they can grow. In addition, as the planet warms (a result of our carbon emissions), we will see more drought in many places, and this will affect the amount of water available for plants’ growth.


Carbon dioxide (CO2) is:

Natural sources of atmospheric carbon dioxide come from the breathing of organisms, weathering of certain rocks, and volcanic eruptions from venting volcanoes. Carbon dioxide from human activities, like the burning of fossil fuels, is harmful, leading to a rise in Earth’s surface temperature, the melting of ice sheets and glaciers, more weather extremes, sea level rise, and other consequences.


Carbon dioxide is not the only carbon-containing compound in the atmosphere researchers are studying. What else are scientists looking at?

Carbon dioxide is not the only carbon-containing compound in the atmosphere that affects our climate. Methane (which comes from livestock, leakage from and venting of natural gas systems, and wetlands) is a potent heat-trapping greenhouse gas. Carbon monoxide (which comes from unvented heaters and generators and other gasoline-powered equipment) affects methane, carbon dioxide and ozone levels in the atmosphere. Because carbon monoxide lingers in the air for about a month it can travel long distances, making it useful for studying how air pollution moves around the world. Black carbon (soot) is the byproduct of burning fuels like petroleum and coal. When black carbon settles on ice and snow in the Arctic and Antarctic or on mountain glaciers it darkens the surface of the snow, speeding up melt and reducing freshwater availability.


People have been concerned about the rise in carbon dioxide in our atmosphere, the result of human activity, since what period of time?

The idea of global warming goes back to the Victorian Age. In 1856, Eunice Foote discovered that carbon dioxide (CO₂) and water vapor in Earth's atmosphere trap escaping infrared (heat) radiation, acting like a blanket to keep the surface layers warm (the greenhouse effect). John Tyndall independently confirmed the discovery a few years later. In 1896, Svante Arrhenius was the first to calculate how much CO₂ contributes to the greenhouse effect and speculated that changes in the amount of CO₂ in the atmosphere contributed to variations in Earth's climate. He also linked the burning of fossil fuels to climate warming, a link we clearly see today.


What role does the ocean play in the carbon cycle?

The ocean's surface both releases carbon dioxide into the air and absorbs or stores it. One-third of all carbon dioxide emitted by humanity has been absorbed by the world’s ocean. This is making them more acidic than they have been for millions of years. More acidic seawater has negative effects on coral reefs, slowing their growth and bleaching them. A more acidic ocean is affecting plankton (which provide half of the oxygen we breathe) and many marine organisms. Due to global warming, the capacity to provide oxygen and support the ocean's food chains has fallen by 6% over the last 30 years. The net result is that the ocean continues to store more carbon dioxide than it emits.