What Process Adds Carbon Dioxide to the Air

What Process Adds Carbon Dioxide to the Air

Carbon dioxide (CO2) is the 5th nearly abundant gas in the atmosphere and, together with water vapor, probably the all-time known of the greenhouse gases.

Virtually everyone agrees that human activities are

causing the atmospheric concentration of carbon dioxide to slowly increase.   We’ll look at some of the experimental evidence in a moment.

Not everyone agrees still about the effect that increasing amounts of


will take on the earth’southward energy budget and climate.  The worry is that increasing greenhouse gas concentrations will strengthen the greenhouse effect and will cause the earth’south surface to warm.

It is important to recollect that the greenhouse outcome isn’t all bad, it has a beneficial side.   You might refer to this every bit the natural greenhouse effect (i.east. one that has non been affected or influenced by human being activities)

If the earth’s atmosphere did not comprise whatever greenhouse gases, the global annual boilerplate surface temperature would be about 0o
F.  That’s cold enough and that’s the average, at that place would be many locations much colder than that
  The presence of greenhouse gases raises this boilerplate temperature to well-nigh lxo
F and makes the earth a much more habitable place.

  Then some warming is a good affair.

The concern is that increasing atmospheric greenhouse gas concentrations might cause some additional warming (and we rely on calculator models to predict or estimate how much warming there volition exist).  This lone might non sound like a bad thing.  However even a small-scale alter in average temperature might

melt polar water ice and cause a rise in

sea level which, at the very least,  might pose an ecology threat to coastal areas.  Warming might change conditions patterns and bring more than atmospheric precipitation to some areas and prolonged drought to other places (like Arizona).  Serious tropical diseases (such equally malaria and dengue fever) might spread into more than temperate areas.  Plant and animal species might be forced to migrate in order to find a suitable surround; some might not be able to arrange quickly enough and could get extinct.

We will salve much of that discussion for later in the semester, h
ere we will just concentrate on carbon dioxide.

First some of the experimental data that show atmospheric carbon dioxide concentration is increasing.

This is a sketch of the “Keeling” curve.  It shows measurements of CO2
that were begun (past a graduate educatee named Charles Keeling) in 1958 on top of the Mauna Loa volcano in Hawaii (the air there is “make clean” and non affected by nearby cities and other sources of pollutants).  Carbon dioxide concentrations were virtually 315 ppm when the measurements began and just reached 400 ppm earlier this year (the figure above is a niggling out of date).  to virtually 385 ppm betwixt 1958 and the present 24-hour interval.  The small wiggles (one jerk per year) bear witness that CO2
concentration changes slightly during the grade of a twelvemonth (information technology probably as well changes slightly during the course of a solar day).

Yous can find the latest measured

atmospheric CO2
concentration at Mauna Loa Observatory at an interesting, interactive site maintained by the Scripps Institution of Oceanography.  Click on the “full record” box at the bottom of the graph to see the complete Keeling record.

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The summit of Mauna Loa is left of center

on this paradigm of the “large island” of Hawaii.

(source of this paradigm)

Once scientists saw this data they began to wonder about how COii
concentrations might have been changing prior to 1958.  But how could you lot now, in 2013 say, get back and measure the amount of COtwo
in the atmosphere in the past?  Scientists have establish a very clever style of doing just that.  It involves coring down into ice sheets that take been building upward in Antarctica and Greenland for hundreds of thousands of years.

As layers of snow are piled on top of each other year after year, the snow at the bottom is compressed and eventually turns into a thin layer of solid ice.  The ice contains small bubbles of air trapped in the snow, samples of the atmosphere at the fourth dimension the snow originally cruel.  Scientists are able to date the ice layers and then take the air out of these bubbles and measure out the carbon dioxide concentration.  This can’t be very easy, the layers are very thin, the bubbles are small and it is hard to avoid contagion.

(source of this epitome)

Using the ice cadre measurements scientists accept determined that atmospheric CO2
concentration was adequately constant at about 280 ppm between 0 AD and the mid-1700s when it started to increment.  The commencement of rising COtwo
coincides with the commencement of the “Industrial Revolution.”

Combustion of fossil fuels needed to power factories began to add together significant amounts of COtwo
to the atmosphere.

Using the ice cadre measurements scientists have determined that atmospheric CO2
concentration was fairly constant at virtually 280 ppm between 0 Advertising and the mid-1700s when it started to increase.  The start of rising CO2
coincides with the offset of the “Industrial Revolution.”

Combustion of fossil fuels needed to power factories began to add significant amounts of CO2
to the atmosphere.

You tin meet a more accurately drawn version of this graph by going back to the Scripps Institute of Oceanography site and clicking on the “1700 – present” box.  You can see the full 800,000 twelvemonth long record of atmospheric


concentration (from Antarctic ice cores) by clicking on the “800,000 years” box.

The current increase is the largest and virtually rapid in the ice core record.

This effigy with actual information from Climate Change 2007, IPCC 4th Assessment Report, shows that concentrations of two other greenhouse gases, methane and nitrous oxide, have been increasing in much the same mode that



In order to understand why atmospheric carbon dioxide concentration is increasing, and before nosotros expect at what the earth’southward temperature has been doing during this period, nosotros

need to know how carbon dioxide is added to and removed from the atmosphere.

Carbon dioxide is added to the atmosphere naturally by respiration (animals breathe in oxygen and exhale carbon dioxide), decay, and volcanoes.

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Combustion of fossil fuels, a human activity also adds CO


to the atmosphere.Cutting down and killing a tree, deforestation, will keep it from removing CO2
from the air by photosynthesis.  The dead tree volition as well disuse and release CO2
to the air.


is removed from the temper by photosynthesis (the equation is shown above).


also dissolves in the oceans.


means I’m not not enlightened of an anthropogenic process that removes significant amounts of carbon dioxide from the air.  Though carbon sequestration (the capture/removal of


from the air and storage) is something that is being considered to lessen or prevent global warming.

We are at present able to better understand the yearly variation in atmospheric CO2

(the “wiggles” on the Keeling Bend) and can figure out when the highest and lowest


concentrations should occur


We will presume that the release of


to the air remains abiding throughout the year (the direct brown line below).  Photosynthesis (the green curve) will change.  Photosynthesis is highest in the summer when plants are growing actively.  It is lowest in the winter when many plants are dead or dormant.



concentration will decrease as long as the rate of removal (photosynthesis) is greater than the rate of release (blue shaded portion to a higher place).  Your depository financial institution account residuum will drop as long as you spend more money than you eolith.  The minimum occurs at the right cease of the blueish shaded portion where the removal and release curves cross.

One time the curves cross and the green photosynthesis bend drops beneath the brownish curve (charge per unit of release), more


  is being released than removed and the


concentration volition start to increase.  The highest


concentration occurs in one case wintertime is over and the rate of photosynthesis increases and again becomes equal to the rate of release.

To really understand why human activities are causing atmospheric CO2
concentration to increase we demand to look at the actual amounts of CO2
beingness added to and being removed from the temper (like amounts of coin moving into and out of a depository financial institution account and their effect on the account residue).  A simplified version of the carbon cycle is shown below.

The carbon cycle shows movement of carbon into and out of the atmosphere or ocean.

Hither are the main points to have from this figure:


The underlined numbers show the amount of carbon
in “reservoirs.”  For instance

760 units* of carbon are stored in the temper (predominantly in the form of CO2, but as well in small amounts of CH4
(methane), CFCs and other gases; anything that contains carbon).

Note that the temper is a fairly small reservoir.

    The other numbers show “fluxes,” the amount of carbon moving into or out of the atmosphere.  Over land, respiration and decay add 120 units* of carbon to the temper every year.  Photosynthesis (primarily) removes 120 units every year.

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Note the natural processes (color coded blue and green) are pretty much in balance (over land: 120 units added to the atmosphere and 120 units removed, over the oceans: 90 units added balanced by xc units of carbon removed from the atmosphere every yr). If these were the simply processes present, the atmospheric concentration (760 units) wouldn’t modify.


Anthropogenic (human being caused) emissions of carbon into the air are minor compared to natural processes (orange in the figure).  Virtually

6.4 units are added during combustion of fossil fuels (and during the manufacture of cement) and

1.6 units are added every twelvemonth because of deforestation (when trees are cut down they decay or are burned and add COii
to the air, also because they are dead they aren’t able to remove COtwo
from the air by photosynthesis)

The rate at which carbon is added to the atmosphere by man is not counterbalanced by an equal rate of removal: near half (four.6 of the 8) units added every year are removed (highlighted in yellow in the figure).

This modest imbalance (8 – four.6 = 3.half dozen units of carbon are added to the atmosphere every twelvemonth) explains why atmospheric carbon dioxide concentrations are increasing with fourth dimension.

  Note also that more than carbon dioxide is added to the oceans every year than is removed.  Addition of


to the oceans might increment the acidity of the body of water h2o which might might make it more than hard for coral and sea shells to course (shells and coral are made of calcium carbonate Ca



In the next 100 years or so, the 7500 units or so of carbon stored in the fossil fuels reservoir (lower left hand corner of the figure) might exist dug up or pumped out of the ground and burned.  That would add 7500 units of carbon to the air.  The big question is how

will the atmospheric concentration alter and what effects will that have on climate?  Carbon dioxide can move into and out of the atmosphere adequately quickly, movement into and out of some of the other reservoirs is ho-hum.  Thus information technology is difficult to say precisely how and how quickly the motion picture will modify when it is perturbed.

*don’t worry about the units.  But hither they are just in case y’all are interested:
Reservoirs – Gtons
Fluxes – Gtons/year

A Gton = x12
metric tons. (i metric ton is 1000 kilograms or about 2200 pounds)

So hither’s where nosotros’re at.

Atmospheric CO2
concentration was fairly abiding between 0 Advertizement and the mid 1700s.
concentration has been increasing since the mid 1700s.
The obvious question is what has the temperature of the world been doing during this period?

In particular has there been any warming associated with the increases in greenhouse gases that have occurred since the mid 1700s?  The respond to that question will be the discipline of a futurity 1S1P report topic.

What Process Adds Carbon Dioxide to the Air

Source: http://www.atmo.arizona.edu/students/courselinks/spring13/atmo170a1s1/1S1P_stuff/carbon_dioxide/atmos_carbon_dioxide.html