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CO2 – the major cause of global warming

Global warming is caused by the emission of greenhouse gases . 72% of the totally emitted greenhouse gases is carbon dioxide (CO2), 18% Methane and 9% Nitrous oxide (NOx). Carbon dioxide emissions therefore are the most important cause of global warming. CO2 is inevitably created by burning fuels like e.g. oil, natural gas, diesel, organic-diesel, petrol, organic-petrol, ethanol. The emissions of CO2 have been dramatically increased within the last 50 years and are still increasing by almost 3% each year, see graph below:


Word-wide CO2 emission are steadily increasing

Graph 1: CO2-emissions world-wide by year (data from



World-wide CO2 emissions and concentrations
Graph 2: CO2 emissions world-wide by year and CO2 concentration in the atmosphere by year


The carbon dioxide is released to the atmosphere where it remains for 100 to 200 years. This leads to an increasing concentration of carbon dioxide in our atmosphere (see above on the right hand side), which in turn causes the average temperature on Earth to raise (see graph below).


Increase of world temperature


Chart 3: Increase of global average temperature for the last 20 years (source:


Recent investigations have shown that inconceivable catastrophic changes in the environment will take place if the global temperatures increase by more than 2° C (3.6° F). A warming of 2° C (3.6° F) corresponds to a carbon dioxide (CO2) concentration of about 450 ppm (parts per million) in the atmosphere.

As of beginning of 2007, the CO2 concentration is already at 380 ppm and it raises on average 2 – 3 ppm each year, so that the critical value will be reached in approximately 20 to 30 years from now. See here for some graphs about the increasing concentration of greenhouse gases and the greenhouse gas emissions by sector.


Mitigation goals for the main cause of global warming: carbon dioxide emissions 

As a result of the above mentioned findings, there seems to be a consensus among the leading developed countries that the temperature increase caused by global warming must not exceed 2° C (3.6° F). For example the European Union (EU) has committed itself to this threshold already in 2005.

To reach this target the annual global CO2 emissions have to be reduced from about 28 Gigatons in 2006 to 20 Gigatons of CO2 by the year 2050 and to 10 Gigatons of CO2 by the year 2100 according to IPCC. At the first glance, this does not look like a major reduction. However one should keep in mind that the world population will grow from 6.4 billion people in 2007 to about 9.5 billion people in 2050. At the same time more and more developing countries will progress their industrialisation and as a result they will want to copy our western life style causing high CO2 emissions.

The world-wide average CO2 emissions by capita was about 4 tons per year in 2005. For North America it was about 20 tons and for Europe about 10 tons per year per capita. By 2050, the world-wide average CO2 emission per capita needs to be reduced to 2 tons per year. In the following years, the emissions will need again to be cut by half. Download and use our Excel calculator to simulate cause and effects of global warming . Based on an average carbon footprint, you can test ways to mitigate global warming yourself. Alternatively, you can have a look at some simulation results how global warming can be stopped below 2 C


Have a look at the CO2 emissions per capita by country to see how far away from this goal value of 2 tons per year our western life style is.

In a fair world, there is absolutely no justification for the western world to pollute the Earth more than others. So we should aim to reduce our carbon footprint to 2 tons per capita per year until 2050. This means people in industrialised nations will have to cut down their carbon dioxide emissions to values reaching 10% to 20% of the current values.

The above mentioned goal can only be reached if our life style becomes a sustainable one. The first and most efficient measure is a reduction of our energy consumption. In addition, it is inevitable to make thoughts about the true meaning of life and change our personal behaviour accordingly.



ΞCarbon dioxide | earth | Global warming

81 thoughts on “CO2 – the major cause of global warming”

  1. who wrote this page
    who wrote this page? I need their name for a research paper i am doing
    peace and love

    1. The author of most pages

      Like most of the articles on this website, it has been written by Juerg Rohrer from

      This page about the main cause of global warming was last updated in July 2007.

      1. Co2 & temperature data set
        may I get the data set that generated the graph in the middle of the page

        Co2 and temperature?

        The graph looks like a linear regression and I would like to use it in my class (I teach statistics to MBA students)

        Thank you

        Russ Robins

        1. I cannot find this information!
          What percent of the infrared radiation spectrum can carbon-dioxide molecule absorb?
          What percent of the infrared radiation spectrum can nitrogen molecule absorb?
          What percent of the infrared radiation spectrum can oxygen molecule absorb?
          What percent of the infrared radiation spectrum can methane molecule absorb?

          1. Article poster in 2007
            Isn’t it about time for an update or a retraction of part or all of this “scientific” opinion.

          2. Greenhouse gases
            Unless I am mistaken, NOx is not a greenhouse gas. N2O is. NOx breaks down CH3 in sunlight.

        2. I did, my name is sarah
          I did, my name is sarah bongeot and i am encouriging australians to help me stop this crisis before it goes too far

          1. im confused is there any chance you could help me please.???
            i have homework that tells me to name 2 gases that contribute towards global warming.
            can you help please.:) x

        3. water vapor: effect on global warming
          why are you ignoring water vapor as a source for global warming. It seems most global warming advocates tend to ignore that fact as well. is there a reason for this? supposedly water vapor is responsible for 95% global warming, and 99.99% of water vapor is naturally formed.

          1. Water vapor is the most important NATURAL greenhouse gas

            Water vapor is indeed the most important naturally occurring greenhouse gas. The major natural greenhouse gases are water vapor, which causes about 36-70% of the greenhouse effect on Earth (not including clouds); carbon dioxide CO2, which causes 9-26%; methane, which causes 4-9%, and ozone, which causes 3-7%. It is not possible to state that a certain gas causes a certain percentage of the greenhouse effect, because the influences of the various gases are not additive. Other greenhouse gases include, but are not limited to, nitrous oxide, sulfur hexafluoride, hydrofluorocarbons, perfluorocarbons and chlorofluorocarbons.

            But the fact that water vapor is the most important gas in creating the natural greenhouse effect does not mean man-made greenhouse gases have no effect!

            Since we cannot influence the naturally occurring greenhouse gases, we normally concentrate on the man-made greenhouse gases (many times without specifically mentioning). Sometimes they are called "emitted greenhouse gases". I understand that this can be confusing.

            Cause and effect of global warming

            Increasing amounts of man-made greenhouse gases lead to an increase in the surface temperature on Earth. This temperature increase causes other effects, one of them being the increase of the amount of water vapor in the atmosphere. Although human activities do not directly add significant amounts of water vapor to the atmosphere, warmer air can contain more water vapor. Because water vapor is a greenhouse gas (as you mentioned), global warming will be further enhanced by the increased amounts of water vapor. This is called a positive feedback.

            In other words:

            1. The current global warming is caused by man-made greenhouse gases (mainly CO2, NOx and Methane).
            2. Global warming leads to a higher temperature on Earth.
            3. Due to the higher temperature, the air does contain more water vapor.
            4. This additional water vapor (a greenhouse gas) does again increase the effect of global warming (a positive feedback or secondary effect).



              It has been shown over & over that co2 actualy has lagged warming by anywhere from 600-800 years. There is a naturally occuring cycle of warming of about 1500 years that is in fact, unstoppable. Humans have been on the earth for a tiny fraction (think of it as the last 15 seconds of a year) of it’s existance and it is the height of arrogance & narcisism to think we are the cause of a naturally occuring climate cycle. Why do you people insist on thinking that our present temperatures are the optimum?

              1. The cause for the current global warming is a different one
                The Earth has indeed already had warming periods for several times, as you mentioned. However there is not just one single way to initiate a global warming period. Who is saying that all global warming periods have been caused by the same effect?

                So earlier warming periods may easily have been caused by different effects than the current one. In fact, most of the earlier global warming periods have been caused by a change in the sun’s radiation. In that particular case it is normal that the CO2 concentration lags behind the warming because it is a secondary effect and not the cause.

                The current global warming however is caused by man-made emissions of greenhouse gases. It is meanwhile well proven not to be a natural cycle.

                You can fracture your leg with skiing, but you can also fracture your leg if you fall down the stairs. If you fractured your leg already two times with skiing, this is no proof that in the third case it was caused by skiing as well. Maybe you have had a car accident or anything else.

                It is similar with the cause of global warming: The cause for earlier warming periods can be (and indeed are) different from the current one.

                1. Some more data.
                  Actually, considering clouds, water vapor causes from 66-85% of green house effect. I also have to state that the wikipedia page where you took your percentages is edited. It is absolutely not true that CO2 might ever cause 9-26% of the green house effect. + the concentrations of CO2 you show on your website are wrong as in the fact that the human influence of them is most likely nothing. We dont emit more than a few percents of the annual CO2 emissions. Actually oceans emit about 80% of it, if not more, meaning more than 100x what we may emit every summer when oceans warm up.

                2. Water Vapor
                  Does that mean that if we use Hydrogen powered cars which they say are healthy for the enviroment, then we could in fact be endangering it? I for one am not up for hydrogen-powered cars because they are very dangerous. Scientists also say that hydrogen-powered cars create water vapor. So this is why I am asking.
                  Thank you, Hector.

                  1. CO2 is causing global warming

                    Compared to the water vapor which is already in the atmosphere, the additional water vapor generated by hydrogen-powered cars would have very little influence.

                    The problem with hydrogen-powered cars is the generation of hydrogen. At the time being, there is no very efficient and clean technology available for the creation of such amounts of hydrogen.

                    We can turn it as we want: we will have to reduce our energy requirements in the developed world. We are definitely consuming too many resources. Our current lifestyle is very far away from being a sustainable one.

                    1. global warming/climate change
                      last october was the coldest in 74 years temperatures are dropping all over the globe and global warming has now been changed to climate change can you explain this? Doesn’t this contradict the whole C02 greenhouse effect?

                      1. Global warming / climate change / major causes

                        You need to look at the yearly average temperature. Just to take one month and then draw conclusions is not appropriate. All in all, the wheather is getting more extreme, so we will have much wormer and much colder days, weeks and months in a year. We will have periodes with extremely high precipitations and periodes with aridity. The same is true for storms, tornados, etc.

                        What you see in the graph above is the yearly average temperature of the world (not just in the place where you are living). And this yearly average temperature of the world has been increasing.


                        1. Not at all, the sun has been
                          Not at all, the sun has been at it’s lowest output for a hundred years or so. It is struggling to wake, even now. And still the GLOBAL temperature continues to rise.

                          1. Not at all, the sun has been
                            The sun has a solar cycle intensity of 11 years and a magneto sphere intensity of 26 years. Not sure where you got 100 years.

                          2. Water Vapor
                            We are releasing more water vapor that Co2. Anytime anything of organic orgin is burned you get h2o and co2 and energy. The more we burn the more water vapor is produced.

                            1. Burning fuels creates more CO2 than water vapor

                              You are WRONG when you say

                              "We are releasing more water vapor than CO2".

                              For example, let’s look at burning diesel fuel. Burning fuel is called an oxidation process. To make it simple, we assume C12H26 as chemical formula for diesel fuel. Then the following chemical reaction takes place:

                              2 C12H22 + 37 O2 → 26 H2O + 24 CO2

                              This means: for each kg of diesel fuel burnt, 1.38 kg water vapor and 3.106 kg CO2 is produced. So the oxidation of diesel fuel creates more than two times as much carbon dioxide (CO2) as water vapor. The relation for other fossil fuels is similar (but not exactly the same).

                              1. You’re not considering the number of molecules or moles
                                Your equation of the oxidation of diesel fuel shows the production of 26 water molecules to the 24 molecules of carbon dioxide. Yes, carbon dioxide’s molecular mass is greater, which results in the greater mass of carbon dioxide, but the actual number of molecules is what is more important when considering effects of concentrations of gases in the atmosphere. What level of education in chemistry, physics or biology have you completed?

                                Why are you trying to discount the effect of water in the atmosphere? When that water comes out the exhaust pipe it carries a lot of heat with it. Water absorbs infrared radiation as well. So why shouldn’t people be concerned with the production of heated water vapor by oxidizing organic matter of any kind? Why is the focus only on CO2? Shouldn’t people be concerned with any activity that increases the amount of heat released into the atmosphere, whether from an electrical stove to a nuclear reactor, to the hot paved roads that emit a lot more heat under direct sun than gravel, dirt or especially plant cover?

                                1. Greenhouse effect CO2 and water vapor

                                  I am certainly not denying the effect of water for the (natural) greenhouse effect. However, if you took 12’000 molecules of air, you would normally find just 3 molecules of CO2 but 600 molecules of water. So if you add 26 more water molecules to 600, the relative change is quite little compared to adding 24 carbon dioxide molecules to the existing 3 CO2 molecules.

                                  However, it is not just the number of molecules as you seem to suggest: the strength of greenhouse effect of the different contributors also needs to be taken into account. With increasing height, the concentration of water vapor drops significantly, where the concentration of other greenhouse gases like CO2 or Methane remain more or less constant with increasing height above ground. Because it is colder up there, greenhouse gases are much more effective with increasing height above ground. 

                                  Water vapor and clouds account for about 65 to 85% of the natural greenhouse effect (natural means without human acitivities). The remaining 15 to 35% of the natural greenhouse effect are caused by very small concentrations of the other greenhouse gases (CO2, NOx, Methane, etc.). This explains why relatively small quantities of CO2 and other non-water greenhouse gases can have a major effect on the climate.

                                  Human beings have been increasing the amount of non-water vapor greenhouse gases in the atmosphere (mainly due to burning fossile fuels, cattle breeding, etc.). This causes the temperature to rise. In addition, an increased temperature causes more water to water to evaporate into the atmosphere, which does in turn increase the warming effect.

                                  See also the comment about water vapor and natural greenhouse gases.

                              2. How do we know the increase in CO2 levels is due to man ?
                                I remember reading somewhere that the reason it has been conjectured that the CO2 concentration gains were due to burning fossil fuels, and the reason we know this is so is due to a decrease in Carbon 14 in these levels, since fossil fuels are old enough to lose all of it’s Carbon 14 content.

                                However, I also remember reading about atmospheric atomic bomb testing since the 50s, which contaminated the atmosphere with C14, which will stick around for a very long time to come.

                                Since burning a fuel requires oxygen, and since oxygen is contaminated, how do we know that any increases in C02 levels are due to man ?

                              3. carbon monoxide
                                what is carbon monoxidde in chemical lanuage like co2? i need to know for a assignment

                                  1. carbon monoxide
                                    its actually CO2, btw its not called “carbon monoxide” its called carbon dioxide

                              4. Carbon Dioxide (CO2) and Carbon Monoxide (CO)
                                Why is carbon monixde not a problem? Does it not contribute to global warming? Does a vehicles emissions contain more CO2 than CO?

                                Also, i have read that CO2 is 1 1/2 times heavier than air. WHy wouldnt the CO2 be down at the ground level rather than rising higher than normal air up to the stratosphere?

                                Thanks for you response in advance.

                                1. carbon monoxide is turned
                                  carbon monoxide is turned into Carbon dioxode when it is mixed with enough oxygen.

                                2. Carbon dioxide and carbon monoxide

                                  The air is a mixture of different compounds, usually about 21% oxygen (O2) and about 78% nitrogen (N2). We have this mixture although nitrogen is lighter than oxygen. So the same question can be asked for nitrogen and oxygen in the air.

                                  The anwser is: Air is a so-called meta-stable gas mixture, the concentrations remain constant up to a height of about 100 kilometers. The air is constantly agitated (e.g. by winds) which helps to keep it
                                  well mixed and to lower existing differences in concentration.

                                  Emission of CO:

                                  A modern vehicle should not emit much CO because CO is a sign of a bad (incomplete) burning process. Usually because oxygen was missing. The catalyst in the vehicle should convert CO into CO2.

                                  CO is dangerous for human beings and for plants. Just mixing it with oxygen is not enough to transform it into CO2, it needs further activation (catalyst, sun light, etc.)


                                    1. ppm = parts per million
                                      ppm means “parts per million”, i.e. 10’000 ppm = 1%


                                3. the cycle
                                  think of it like this.

                                  warmer climate = ice melts

                                  ice melts = more condensation( more rain)

                                  more rain = more plants growing and thriving

                                  more plants and trees = less Co2

                                  less co2 = steady climates on earth

                                  nature has its own way of fixing things, humans have disrupted this cycle.

                                  instead of trying to slow down human carbon monoxide and co2 emissions plant more trees and nature will do the rest.

                                  i dont understand how no one else has thought of this…

                                  Antonio McCoy

                                  1. CO2 emission and carbon cycle


                                    The problem is that you cannot offset all additional greenhouse gases by planting more trees. You needed an additional earth to get enough space…

                                    Another problem is that actually deforestation is taking place – just the opposite what would help. Main reasons: People want additional fields for cattle breeding and additional fields for growing animal food. 

                                  2. You obviously haven’t
                                    You obviously haven’t thought of or know what albedo is! Ice is able to reflect more light (we see it as white), but when ice melts (turns to water) its absorption shifts and is able to absorb more light which causes more ice to melt etc…

                                    I think this is a big runaway problem that needs to be looked at more!

                                  3. Many people are wanting to
                                    Many people are wanting to destroy the forests to make way for development. A major example of this i in the Amazon where people are burning the rain forests to build houses. This means that not many people want to plant trees. Many people who are destroying the rain forests come from poorer backgrounds and are dependant on this source of income.

                                  4. santhosh(india)
                                    yes ….. respected sir””””””””’ i am very thankfull to you first of all togive a good information about our earth climate cycle…….. this is really no body knows…
                                    i inspired regarding about our earth climate…………..
                                    i have already so many thoughts how to reduce global warming…….. so im going to impliment my thoughts in my country………………
                                    so please sir help me by giving good advices( your thoughts)

                                    my name; santosh…

                                  5. Change thinking to chane the cycle
                                    I aggee, this makes perfect sense, but the thing that stands in the way is profit. People are obsessed with the dollar.
                                    The only way to stop this is to make it more profitable for people to cultivate and protect the forest. The old saying or poacher turned gamekeeper springs to mind. What we need is the governments of the world to spend less on arms and use the money to incentivise the protection of the forests, before it’s too late.


                                4. How?
                                  How CO2 change the temperature?
                                  How CO2 rises the temperature?
                                  I am just curious to know how, and why.

                                  1. Co2 prevents some of the heat
                                    Co2 prevents some of the heat to escape, make the atmosphere heavier and more humid so to speak.

                                5. greenhouse effect
                                  Exactly how does CO2 cause global warming? I am interested in the physics/chemistry of this effect. Does CO2 actually not allow heat to escape the earth? The physics of this does not make any sense to me.

                                  1. gases like c02 form a bubble
                                    gases like c02 form a bubble around the earth that let in the solar radiation, but prevent it from escaping. This means the earth will gradually get warmer and warmer

                                    1. global warming
                                      can someon plz help me write a letter to a industry regarding global warming. like it has to incude wat dA industry is doing to prevent climate change. i would like to write to the coal industry or oil but i dont know wat to write and my assignment is due really soon.

                                6. Where’s water vapor
                                  Quite odd that you don’t include water vapor in your list of greenhouse gases. If you take a look at the IR absorption spectrum of H2O vs CO2, you immediately see that CO2 is a very weak IR absorber and H2O is very strong. Additionally, from a concentration perspective, CO2 is less than 1% of our atmosphere. H2O, while variable, is multiple percents of the atmosphere.

                                  Sort of odd that you omit the most important of greenhouse gases. Quite a distortion.

                                  1. water vapor
                                    Water vapor is a feedback and not a forcing. If humans add water vapor to the air, the air will saturate and the water will rain down. Humans cannot physically add water to the atmosphere to make concentrations higher. We would have to raise the temperatures first because the water vapor in the air is dependent on the air temperature. CO2 is not dependent on the temperature, it is independent, and the temperature can thus change because it is the dependent variable.

                                    If temperature increases because of other greenhouse gases, however, the water vapor can increase, and since water vapor indeed is a greenhouse gas, the temperature can warm and hold more water vapor. It can reach a point though where it starts to form clouds and cools the Earth.

                                    Another reason why water vapor is not worried about is because it has a short residence time. If I add water vapor to the atmosphere, it will rain out in 7-10 days. If I add CO2 to the atmosphere, it will stay there from decades to centuries. Looking at this, one can easily tell that CO2 can tend to accumulate in the atmosphere.

                                    H2O can absorb more of the IR spectrum than CO2 and not necessarily more heat. So, saying that H2O is a stronger absorber of IR radiation is misleading.

                                    Our atmosphere is 78% nitrogen, 21% oxygen, 0.93% argon and the rest (0.07%) is made up of greenhouse and other various gases. Water vapor in a given area can vary from 0-4% of the atmosphere. To say that CO2 is insignificant because of its concentration is ignorant (and hypocritical if you believe that increased solar activity is responsible for the warming). Less than 0.07% of our atmosphere accounts for about 60 degrees Fahrenheit of warming.

                                7. co2 absorption and immediate btu injection.
                                  They keep talking about the co2 problem holding in the heat but a far more and immediate problem is the heat used from the fuel. In all but fuel cell uses of fossil fuels and coal the fuel is burnt producing huge amounts of heat. Instead of looking at the co2 only they should be looking at the quadrillions of btu’s released every day by industry, autos, and homes.
                                  even most uses of electric produced by wind, solar, and hydro is to heat or pump heat with a btu loss, or run motors at a btu waste. incandescent lighting is 80% heat and 20% light.

                                8. Natural vs. man-made carbon dioxide
                                  what percent of the carbon dioxide concentrations since the Industrial Revolution is from natural means and from man-made means? The amount of carbon dioxide increases by fourty percent but some climate skeptics say that only three percent came from man. Is this true? And what are the major contributors to increases natural carbon dioxide?

                                9. thanks this text helped me
                                  thanks this text helped me alot for my school work

                                10. weight of CO2
                                  The atomic weight of CO2 is 44, much heavier than nitrogen or oxygen. Why then does CO2 stay in the atmosphere? Will it eventually sink out of the atmosphere because of its weight?

                                11. Thanks
                                  Thank you so much for creating this page because it will greatly help me with a section in my climate change summative. All I need to do now is reference this page in APA style. That’s probably the worst part of a science summative! lol! But ya thanks! 😀


                                12. because of my summative
                                  I was just wondering when this page was last updated because I am doing a summative for school and I have to reference and do in text citations. If you could tell me you would be of great help! 😀 Thanks.

                                  Rebecca (again lol) 😛

                                13. Is carbon dioxide the cause of global warming?
                                  I’m doing a project at school about the possible causes of global warming. Is there any more evidence that suggests carbon dioxide (or other things) are the cause of global warming?

                                14. I NEED 3 NUMBERS!
                                  What percent of the infared radiation spectrum can the carbon-dioxide molecule absorb?
                                  What percent of the infared radiation spectrum can the oxygen molecule absorb?
                                  What percent of the infared radiation spectrum can the nitrogen molecule absorb?

                                15. What date was this published
                                  i need the date for my science project on co2 emissions, for my bibliography. Would apprecate if answered soon thank you

                                16. percentage of emissions
                                  the percentages really helped me write my paper. Thanks!

                                17. What evidence
                                  What evidence from other sources did you use to back up this theory? Sorry for asking, I just need to know for my course work

                                18. nitrous oxide
                                  Isn’t nitrous oxide supposed to be N2O instead of NOx ? Just curious. If it is correct, do tell me. Thanks.

                                19. responsibilities….
                                  INDIA is much better than EUROPE AND you will too accept it soon.

                                20. confusion
                                  Organic diesel comes from plant life, it cannot produce what the plant did not provide, There is an equal trade

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