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 wri.org)

 


 

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: wri.org)

 

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.

 


 

Comments

who wrote this page

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

The author of most pages

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

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

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.

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).

Juerg

 

SO WHY DOES CO2 LAG BEHIND WARMING?

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?

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.

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.

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.

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.

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?

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.