Mike Adams, the founder of the anti-science and anti-medicine (actually, anti-reality) website NaturalNews, is perhaps one of the most prolific cranks on the Internet. He subscribes to a wide range of absurd pseudoscientific beliefs and spreads dangerous and harmful myths about vaccines, peddles anti-GMO propaganda, promote homeopathy and distrusts the germ theory of disease and even rejects the strongly evidence-based position that HIV is the cause of AIDS (website links in the reference section). This makes him a sort of global crank and an example of crank magnetism. Adams recently wrote an ignorant compilation on NaturalNews called “Al Gore backlash: Why environmentalists are celebrating rising CO2 levels” were he repeated a number of stale climate change denialist talking-points.
In reality, more carbon dioxide will indeed provide a fertilization effect, but we have to remember that climate change does not just involve an increase in carbon dioxide, but also temperature, which means that the fertilization effect is moderated by heat stress. Furthermore, even if carbon dioxide is in excess, other reactants such as nitrogen becomes limited thereby down-regulating photosynthesis. Carbon dioxide has far-reaching climate effects because of interactions and feedback systems. It is unreasonable to use the fact that there has been higher concentrations of carbon dioxide in the past, because the problem is the rapid change in carbon dioxide and temperature, not absolute levels per se. Finally, natural sources and sinks of carbon dioxide more or less balance, but it is the extra addition on carbon dioxide from anthropogenic sources that matter because it brings a net positive addition of carbon dioxide to the atmosphere.
Basically, if Mike Adams just checked the list of common climate change denialist arguments over at Skeptical Science, he would not have to write such an intellectual embarrassing post. Then again, it would probably be an intellectually embarrassing post about something else.
CO2 fertilization exists, but the story is more complex
It is true there is a fertilization effect of carbon dioxide. However, this will mostly benefit C3 plants and have little impact for C4 plants. Additionally, global warming comes with increased temperatures that contribute to heat stress for the plant, which would counteract part of the fertilization effect.
If carbon dioxide is added in excess, other nutrients may become limiting such as nitrogen. Nitrogen is important for a key enzyme in the dark reactions of photosynthesis called Rubisco. A fertilization effect will tend to dilute the nitrogen concentration in biomass and thus down-regulate photosynthesis.
CO2 has far-reaching climate effects
Adams makes a big deal that the absolute concentration of carbon dioxide seems low (400 ppm). However, more carbon dioxide in the atmosphere can have far-reaching consequences. By itself will cause a few degrees of warming, but it will have other feedback effects as well: the increase in temperature will cause more carbon dioxide to enter the atmosphere from the ocean, release methane from the arctic, contribute to desertification, melting of ice etc. that all in turn contribute to direct warming or indirect warming through the release of greenhouse gases.
Organisms have a hard time adapting to rapid increase in CO2 and temperature
While it is true that both the temperature and the atmospheric carbon dioxide concentrations have been higher in the past, the changes that occurred were very slow on a geological time scale giving plants and other organisms enough time to evolve and adapt to the changing environments. When these kinds of climate changes occurs on the timescale of just a few centuries, it may be too quick for many species to adapt. That is one of the reasons for why we should be concerned by rapid increase in carbon dioxide and temperature.
Carbon dioxide, warming and coral bleaching
Corals that form reefs constitutes a biological partnership between a polyp from the phylum Cnidarian and a zooxanthellae. This latter partner performs photosynthesis and feeds the polyp with carbohydrates and the polyp protects the zooxanthellae and provides some nutrients. When higher sustained temperatures occur, this partnership breaks down and the zooxanthellae algae is ejected. It is this that gives the reef corals their color, so they become “bleached”. The breakdown of symbiosis can kill the coral and coral mass death occurs due to ocean warming.
Comparing natural and anthropogenic emissions of CO2
Similar amount of carbon dioxide is released as is absorbed from natural non-anthropogenic processes. However, when humans dig up fossil fuels and burn them, we are releasing carbon dioxide that was not in circulation into the atmosphere. This means that we contribute a net increase, even though it is not comparable to the total amount of carbon dioxide. A helpful analogy is diet: the argument that human emissions are negligible in size compared with natural release is kind of like claiming that you cannot possibly gain weight by eating 500 extra food calories per day, because these 500 food calories is very small compared with your total intake (say, 4000 food calories). The key thing missing is of course the fact that you also, according to this argument, spend 4000 food calories per day. Still, eating 500 more food calories per day will cause you to gain in mass.
Refutation of most climate change denialist assertions: Skeptical Science.
Global warming and coral bleaching: How global warming is driving mass coral bleaching.
CO2 fertilization: CO2 is plant food.
Human versus anthropogenic emissions of CO2: How do human CO2 emissions compare to natural CO2 emissions?.