Why does the level of carbon dioxide in the atmosphere rises slightly in the summer and falls in the winter?

Answer 1

In a typical year the levels are high in May and low in October.

The Northern Hemisphere has much more land for vegetation to grow on compared to the Southern Hemisphere. Carbon dioxide (CO2) builds up slowly during the northern winter, when trees and plants are dormant. Then in May everything begins to grow, and CO2 is taken out of the atmosphere, so the levels start coming down. In October and November vegetation stops growing, and in its dormant state it stops absorbing CO2, so the carbon in the atmosphere increases. These levels go up and down like this every year.

The readings for 1958, 1959 and 1960 show this:

1960: May: 320.5 ppm: October: 314.5 ppm

1959: May: 320.0 ppm: October: 313.5 ppm

1958: May: 318.0 ppm: October: 313.0 ppm

Ppm means parts per million, so 320 ppm is the same as 0.032 percent (per hundred).

The recent readings for May are:

2012: 396.78 ppm
2011: 394.35 ppm

2010: 393.22 ppm

2009: 390.18 ppm

See the graph at the link below.

Answer 2

The levels of atmospheric carbon dioxide fluctuate each year due to the increased combustion of fossil fuels. This is based on continuous measurements taken at the Mauna Loa Observatory in Hawaii.

Answer 3

CO2 levels fluctuate on an annual basis because the majority of the earth's land mass, where plants are present to absorb C02 during photosynthesis, is in the northern hemisphere. When it is summer in the northern hemisphere, the increase in overall photosynthetic activity causes a drop in atmospheric CO2 concentrations. However, when it is summer in the southern hemisphere, there is less net photosynthetic activity on earth, so the atmospheric CO2 level spikes.

Answer 4

The northern hemisphere has a much larger land area suitable for vegetation than the southern hemisphere. During spring and summer in the northern hemisphere all vegetation is growing, and growing vegetation (trees, leaves, plants, grasses etc) absorbs carbon dioxide (CO2) from the atmosphere in the process known as photosynthesis. This means that CO2 levels in the atmosphere are noticeably lower during the northern hemisphere growing time. When autumn and winter arrive vegetation stops growing and the carbon dioxide levels rise in the atmosphere.

Answer 5

Well, each year carbon dioxide levels in the atmosphere change. For example, in the winter there will most likely be more CO2 in the atmosphere. This is because people need to be kept warm in houses and buildings, so fossils need to be burnt (releasing carbon dioxide) in order to be used as fuel for heat.

Another Answer:

Most of earth's land mass is in the northern hemisphere. The death of grasses and decay of leaves emits a few parts per million atmospheric CO2, which is taken up again in the spring as grass grow and trees leaf out again. In the southern hemisphere the same process occurs, offsetting the northern hemisphere change, but to a lesser extent. So a graph of CO2 measurements over the course of a year shows a slight rise and fall of roughly 1%.

Coal burning provides energy to cool houses in the summer, as well as heat in the winter. The gradual rise in CO2 from fossil fuel consumption remains fairly constant from season to season, so the slope of the CO2 rises about 1% per year. For all of human history, and millions of years prior, global atmospheric CO2 never rose above 300 ppm, usually oscillating between 250 and 280 ppm. That is not a very big change. And in prehistoric times, when it DID rise above or fall below those limits, it did so over the course of many thousands of years, changing by well under 1% per century.

At the beginning of the industrial revolution CO2 began rising fairly rapidly, about 1.5% per century. Then from 1900 to 1950 the rate increased to 6% per century. The fifty years following that saw the rate jump from 6% per century to 38% per century. This is the source of the famous "hockey stick" graph of CO2 rise. Within four short decades, at the current rate of increase, atmospheric CO2 will be rising 52% per century. So, before humans, natural CO2 levels changed less than 1% per century, and afterwards over 50% per century.

Another Answer:

CO2 has always varied, mainly due to the varying temperature of our primary method of removing CO2 from the atmosphere, the Northern Ocean. As temperatures increase, water is less able to absorb as much CO2. This, coupled with the fact that 85% of all CO2 comes from nature means that CO2 will always drop in the winter months. (Forests decay slower in the winter). Man's production of CO2 is far smaller then the changes in absorption.

If you look at historical levels of the past 650K years, you will see that CO2 will always follow temperature cycles also. The CO2 levels of our atmosphere have been climbing slowly for the past several centuries, just as the temp has. Typically, CO2 has started to fall about 800 years after we see temperatures start to decline.

Answer 6

That is probably an artifact of the measurement location. Remember, the seasons vary depending upon which equatorial hemisphere one is in.

Well over half earth's land mass is in the northern hemisphere. Plant biomass tends to increase during the summer months, drawing down atmospheric CO2 levels. The leaves and grass die and decay during the winter, returning that CO2 back into the atmosphere. It may take a few months for these seasonal changes to become apparent on remote island atmosphere monitoring stations.

A:In the northern hemisphere (where the larger part of the world's vegetation grows), during the growing season (summer) the levels of carbon dioxide in the atmosphere actually fall (not rise) as the vegetation removes CO2 from the atmosphere. In the winter, when the trees and plants stop growing, carbon dioxide is not taken from the atmosphere. The levels thus rise slightly (not fall, as the question suggests).

Answer 7

Carbon dioxide levels in the atmosphere rise in the Northern Hemisphere spring and summer, when vast amounts of growing vegetation remove the greenhouse gas from the atmosphere. Levels fall slightly then when the growing stops.

Answer 8

Vegetation grows in the Northern Hemisphere Spring and Summer, taking amounts of carbon dioxide out of the atmosphere. Then in winter, it doesn't. This has an effect on the yearly levels, as the Southern Hemisphere does not have enough growing vegetation to balance this.

Answer 9

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