Why do levels of co2 fluctuate

Near the top of the atmosphere, the blue color indicates air that last touched the Earth more than a year before. Download Options x Primary layer of the visualization showing carbon dioxide without overlays like dates, color bars, etc. Download Options x png Color bar for volumetric carbon dioxide. Colors ranging from blues to yellows to reds correspond to the carbon dioxide levels from to parts per million. The curve in the color table is the relative transparency of each value.

Values near ppm and ppm are more opaque and values from ppm and ppm are more transparent. This is often called the natural carbon cycle. But this cycle is affected by the carbon dioxide that humans add to the atmosphere when they burn fossil fuels. The above graph shows the change in carbon dioxide levels measured for the northern hemisphere red , southern hemisphere green and as a global average black.

Because the northern hemisphere contains much more land than the southern hemisphere — which is mostly covered by ocean — the amount of carbon dioxide in the atmosphere increases overall during the northern winter [2].

The annual variation depends on location. In tropical areas, plants are active all year round with little variation between summer and winter. However, in these regions other factors determine the balance between photosynthesis and respiration, such as the availability of nutrients and water, which is vital for photosynthesis. Dufresne, T. Fichefet, P. Friedlingstein, X. Gao, W. Gutowski, T. Johns, G. Krinner, M. Shongwe, C. Tebaldi, A. Weaver and M. Qin, G. Plattner, M. Tignor, S.

Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P. Midgley eds. Lan, B. Hall, G. Dutton, J. Le Floch, B. Bereiter, T. Why is this? Shouldn't it just be constantly going up? The fluctuations are seasonal, which is explained in the web page Seasonal carbon dioxide range expanding as more is added to Earth's atmosphere NSF, summarises the seasonality as being.

Levels of carbon dioxide in the atmosphere rise and fall each year as plants, through photosynthesis and respiration, take up the gas in spring and summer, and release it in fall and winter. Now the range of that cycle is expanding as more carbon dioxide is emitted from burning fossil fuels and other human activities. The magnitude of these seasonal variations differ from location to location. One reason for these variations is the relatively slow mixing between the northern hemisphere and southern hemisphere atmospheres.

It takes about a year for changes in the northern hemisphere atmosphere to make their way into the southern hemisphere atmosphere and vice versa , and even longer for those northern hemisphere changes to migrate to the South Pole. This slow mixing time means that seasonal variations are confined to the hemisphere in which they occur.

There's a large difference between the land to ocean ratio in the northern hemisphere versus the southern hemisphere, and an even greater disparity outside the tropics. The large temperate land mass in the northern hemisphere is the primary cause of those seasonal variations in CO 2 levels in the northern hemisphere. Plants absorb CO 2 from the atmosphere in the spring and summer, and release CO 2 back to the atmosphere in the fall and winter.

Daniel James Jacob, et al.