2010-08-25 14:14:51Basic rebuttal 122. " More Carbon Dioxide will be good for plants and agriculture." REVISION 3.


Version #3 is down below



Unlimited release of Carbon Dioxide

will have negative effects on plants and agriculture


A common argument, made by those who deny Man Made Global Warming, is that the Carbon Dioxide that is being released by the burning of fossil fuels is actually good for the environment. Their argument is based on the logic that, if plants need Carbon Dioxide for their growth, then more of it should be better. We should expect our crops to grow taller and our flower gardens to bloom brighter.

However, this "more is better philosophy" is not the way things work in the real world. There is an older, wiser, saying goes, "Too much of a good thing is a bad thing." For example, one capsule of prescribed medicine might be good for you but three capsules are not likely to be three times better.

As far as plants are concerned, it is possible to help some plants with extra Carbon Dioxide in greenhouses or other enclosed places. It is based on this, that those who deny Man Made Global Warming make their claims. Their claims, however, are simplistic. They fail to take into account that once you increase a substance that plants need, you automatically increase their requirements for other substances.

Plants cannot live on Carbon Dioxide from air alone. They get their bulk from more solid substances like water and organic matter. The organic matter either comes from decomposing plants and animals or from man made fertilizers. Any beneficial effects happen when there is an increase in the amount of water and fertilizer, whether natural or synthetic. Agriculture has been using ammonium nitrate, made from Natural Gas for the past century, to fertilize plants.


So here is where the problem lies. If plants are being given extra Carbon Dioxide in enclosed greenhouses, what would happen if this was done, in the open air, throughout the entire Earth?


1) First, they will need extra water. Where will it come from? If rains are not enough for agriculture then water is taken from wells. The aquifers these waters come from, however, are running dry throughout the world.


On the other hand, as predicted by Global Warming scientists, we are receiving intense storms in certain parts of the world. One would think that this should be good for plants. Unfortunately, when rain falls down that quickly, it does not even have the time to soak into the ground. Instead it quickly floods into creeks, then rivers and finally out the ocean carrying large amounts of fertilizer and soil.


2) Unlike Nature, our way of agriculture does not self fertilize by recycling all dead plants and animals. Instead we have to be constantly producing artificial fertilizer from Natural Gas which will eventually run out. Increasing the growth of crops will increase the need for such fertilizers. This will create competition between the heating of our homes and growing our food, which in turn will drive prices of both up.


3) The worse problem, with adding more Carbon Dioxide to the atmosphere, is that by increasing the temperature throughout the Earth, the deserts will grow. Deserts and other types of dry land are where the least amount of Life grows per square mile. This will create a situation that will drastically reduce, not increase, the amount of plant life that can grow on Earth. 


Also, other eco-zones, whether tropical, forest or grassland will migrate towards the poles, shrinking in size as they do. That will reduce the land area in which plants and animals thrive, further reducing Life on Earth.


In conclusion, it would be reckless to keep adding Carbon Dioxide to the atmosphere.


Even if plants can be made to grow bigger, it would simply create a further strain on water resources and fossil fuel based fertilizers. Even worse, it would reduce the total amount of land area on Earth where plants can grow. 

2010-08-25 18:48:12Suggestions


- Is it necessary to give an example of the argument to be refuted within the rebuttal? I thought that was provided separately.

- I would suggest shortening the descriptions of the influences. 

- It would be useful to have a wrap-up which states: a) all of the influences mentioned above play a role in agriculture, so the final result will depend on all of them; b) this result will depend on the specifics of an area; and c) careful studies which analyze the result by geographical region find a net negative impact on global agriculture.

- I'm not sure of the best reference on c): You could look at 


for more authoritative references.

2010-08-27 10:06:45Title change.



I decided to change the title of the skeptic argument to better capture the attention of the public. They may be more impressed by the word 'agriculture' and it's implications for food (which is always on peoples minds).

I am going to work on shortening it a bit.


2010-08-29 06:05:10


Hi V,

I would drop the 'aspirin' analogy in the second paragraph. It's a good analogy, but argument-by-analogy is not convincing.

In the third paragraph, you could point out that many of the studies showing enhanced plant-growth have been conducted at such high CO2 concentrations (600 ppm and more) that they are way beyond anything that would be survivable for humanity.

I would rephrase the fourth paragraph. Mentioning synthetic fertilizers is not a strong argument in our favour. If the food-yield goes up in step with the added fertilizer, someone could argue that this means we can produce more food from less land, so we can reduce our impact on the environment by leaving more land to go wild! The key point, I feel, is that CO2 is not the factor that limits growth. Maybe try something like this:

"Plants cannot live on Carbon Dioxide from air alone. They also need water, minerals and nutrients. Plant-growth in any ecosystem is limited by one or more of these factors, not by availability of CO2. So adding CO2 alone does not tell us what will happen. We have to look at other factors."

2010-08-29 06:21:18It's region-specific


I think it's essential to make the following point:

- Yes, there are areas where additional CO2 can help, even including the effect on temperature

- However, there are other areas which will be disadvantaged agriculturally by these changes

- Careful studies of the impact, region by region, have shown that the net impact on agriculture over the world will be negative.


2010-08-29 09:23:29TonyWildish



1) "I would drop the 'aspirin' analogy . . ."

I do realize that arguing by analogy is not acceptable amongst professionals. However, I have seen popularized science books and magazines do just that.  They seem to be left with no other choice. 

2) CO2 level sufficient for enhanced plant growth is devastating for Humanity.

I will include that point in a footnote. I do not want to include points that are tangential in the main body of my rebuttal. The reason is, that since the issue of CO2 being harmful is by itself a major talking point, it can easily lead to digression.

It has been my experience, in face to face communication, that if you are talking about a major subject, you should avoid mentioning another major subject that is in dispute in the persons mind. The person will often times get off the subject and start discussing the tangential point.   

So it's best to leave it as an afterthought. 

3) "If the food-yield goes up in step with the added fertilizer, someone could argue that this means we can produce more food from less land, . . ."

I was stressing the impact enhanced growth would have on resources essential for plant growth. Running out of the substance that fertilizer is made of would render any other benefits to agriculture or land conservation moot.

This is all the more important to consider when they realize that the natural gas also heats their homes. You will therefore have competition between the two. 




2010-08-29 18:17:18REVISION 2. At the top.


 REVISION 2. At the top.


2010-08-29 19:30:39


I see your point in 2) (in your reply to me above, not in the revision), it's good to stay on topic. However, your point 3) invites people to go off topic too. You can rapidly diverge into a discussion of peak-gas and peak-oil that way, or someone can tell you that in a warmer world we will not need gas to heat our houses anymore. If someone doesn't believe that we will run out of fossil fuel for fertilizers they could also 'counter' your argument with the argument I proposed about reduced land-use, silly as it is, and you're off topic again.

Also, in the revised draft, I think the last paragraph is not strictly correct. Studies have been conducted in greenhouses, yes, but also in large open spaces. Both do show enhanced plant-growth, but at different levels. In greenhouses, where really high concentrations were maintained, you get significant enhanced growth. So when someone says "CO2 can boost plant growth by 50%", that's what they're talking about. For concentrations we're likely to face in the next century, the enhancement is far less spectacular. Sorry if I didn't make that clear first time round.

2010-08-29 20:50:51TonyWildish. Counter-responses and open air enhancement of plant growth.


. . . someone can tell you that in a warmer world we will not need gas to heat our houses anymore.

Depends on where you live. For every person in the northern latitudes that will supposedly enjoy "balmier" weather, there will be several more in the southern areas that will be consuming more electricity to cool off. Or have to move altogether. 

. . . they could also 'counter' your argument with the argument I proposed about reduced land-use,. . .

We have to keep reminding those we speak to, that the problem with increased temperature is multi-factorial.

The shifting eco-zone issue, and its effect on society, should be foremost in our minds when anticipating any of their counterarguments. I would respond to their 'Utopian retorts' with:

  • "Why do you want your country to turn into a desert so that barely inhabited lands may get a little cozier?"
  • "If there's a change in one place for the better there will definitely be changes in other places for the worse."
  • Then, when I then decide to get sarcastic, "Corn in Siberia. Cactus in Kansas!"

As for your last point on enhanced plant growth in the open, I recall hearing about certain studies showing, that in spite of some growth, there were negative results. Some plants got eaten up alive because they were making more of a certain chemical that attracted pests.


2010-09-02 13:36:32Use of superscript in CO2 and a couple of other points
Patricia Warwick

I believe that it is proper to use a subscript for CO2 not a superscript (CO2)

One argument that is made is that in Canada we will just move our agriculture to higher latitudes. But that land is mostly in the Canadian Shield and there is hardly any soil. Definitely not suitable for agriculture. Other areas are boreal forests and we don't want to make things worse by cutting it down.


2010-09-02 23:42:37Comment
Robert Way

Greenman just did a video on this subject


2010-09-03 13:29:31BASIC rebuttal #122. Revision 3. More Carbon Dioxide will be good for plants and agriculture.