Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.


Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Twitter Facebook YouTube Pinterest MeWe

RSS Posts RSS Comments Email Subscribe

Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...

New? Register here
Forgot your password?

Latest Posts


CO2 is plant food? If only it were so simple

Posted on 27 April 2011 by Dawei

In the climate change debate, it appears to be agreed by everyone that excess CO2 will at least have the direct benefit of increasing photosynthesis, and subsequently growth rate and yield, in virtually any plant species: A common remark is that industrial greenhouse owners will raise CO2 levels far higher than normal in order to increase the yield of their crops, so therefore increasing atmospheric levels should show similar benefits. Unfortunately, a review of the literature shows that this belief is a drastic oversimplification of a topic of study that has rapidly evolved in recent years.

Climate control vs. climate change

The first and most obvious retort to this argument is that plants require more than just CO2 to live. Owners of industrial greenhouses who purchase excess CO2 also invest considerable effort in keeping their plants at optimum growing conditions, particularly with respect to temperature and moisture. As CO2 continues to change the global climate, both of these variables are subject to change in an unfavorable way for a certain species in a certain region (Lobell et al. 2008, Luo 2009, Zhao and Running 2010, Challinor et al. 2010, Lobell et al. 2011). More and more it is becoming clear that in many cases, the negatives of drought and heat stress may cancel out any benefits of increased CO2 predicted by even the most optimistic study. 

But there is a more subtle point to be made here. The majority of scientific studies on enhanced CO2 to date have been performed in just these types of enclosed greenhouses, or even worse, individual growth chambers. Only recently have researchers begun to pull away from these controlled settings and turn their attention to outdoor experiments. Known as Free-Air CO2 Enrichment or “FACE”, these studies observe natural or agricultural plants in a typical outdoor setting while exposing them to a controlled release of CO2, which is continuously monitored in order to maintain whichever ambient concentration is of interest for the study (see Figure 1).

Figure 1 - Example FACE study in Wisconsin, USA with multiple CO2 injection plots; courtesy of David F Karnosky, obtained from Los Alamos National Laboratory.

FACE studies are therefore superior to greenhouse studies in their ability to predict how natural plants should respond to enhanced CO2 in the real world; unfortunately, the results of these studies are not nearly as promising as those of greenhouse studies, with final yield values averaging around 50% less in the free-air studies compared to greenhouse studies (Leaky et al. 2009, Long et al. 2006, Ainsworth 2005, Morgan et al. 2005). Reasons for this are numerous, but it is suspected that in a greenhouse, the isolation of individual plants, constrained root growth, restricted pest access, lack of buffer zones, and unrealistic atmospheric interactions all contribute to artificially boost growth and yield under enhanced CO2.

C3 & C4

Photosynthesis comes in a few different flavors, two of which are C3 and C4. Together C3 and C4 photosynthesis make up almost all of modern agriculture, with wheat and rice being examples of C3 crops while corn and sugarcane are C4. The distinction deals mainly with the specific enzyme that is used to collect CO2 for the process of photosynthesis, with C3 directly relying on the enzyme RuBisCO. C4 plants also use RuBisCO, but unlike C3 plants, they first collect CO2 with the enzyme PEP-carboxylase in the mesophyll cell prior to pumping it to RuBisCO (see Figure 2).

Figure 2 - A simplified diagram contrasting C3 vs. C4 plant photosynthesis. From Nature Magazine.

The relevance of this distinction to excess CO2 is that PEP-carboxylase has no natural affinity for oxygen, whereas RuBisCO does. RuBisCO will just as readily collect oxygen (which is useless) as it will CO2, and so increasing the ratio of CO2/O2 in the atmosphere increases the efficiency of C3 plants; the extra step in the C4 process eliminates this effect, since the mesophyll cell already serves to concentrate pure CO2 near RuBisCO. Therefore excess CO2 shows some benefit to C3 plants, but no significant benefit to C4 plants. Cure and Acock 1986 (a greenhouse study) showed excess CO2 gave a 35% photosynthesis boost to rice and a 32% boost to soybeans (both C3 plants), but only a 4% boost to C4 crops. More recently, Leaky et al. 2006 (a FACE study) did not find any statistically significant boost in photosynthesis or yield for corn (a C4 crop) under excess CO2.

Going a bit deeper, it has recently been found that in some C3 plants—such as cotton and many bean species—a further enzyme known as RuBisCO activase is required to convert RuBisCO into its “active” state, the only state in which it can be used for photosynthesis. The downside of this is that the activase enzyme is much more sensitive to high temperatures compared to RuBisCO itself, and also responds poorly to excess CO2: Heat can destroy the structure of the activase enzyme at temperatures as low as 89.6 F, while excess CO2 reduces the abundance of the cellular energy molecule ATP that is critical for RuBisCO activase to function properly (Crafts-Brandner & Salvucci, 2000, Salvucci et al. 2001). This effect may potentially nullify some of the gains expected from excess CO2 in these plants. 

Chemical Responses & Nutrition

Even within a specific type of photosynthesis—indeed, even within a specific species—the positive responses to enhanced CO2 can vary widely. Nutrient availability in particular can greatly affect a plant’s response to excess CO2, with phosphorous and nitrogen being the most critical (Stöcklin and Körner 2002, Norby et al. 2010, Larson et al. 2010). The ability of plants to maintain sufficient nitrogen under excess CO2 conditions is also reduced for reasons not fully understood (Bloom et al. 2010, Taub and Wang 2008).

It has also been found that excess CO2 can make certain agricultural plants less nutritious for human and animal consumption. Zhu 2005, a three-year FACE study, concluded that a 10% decrease in the protein content of rice is expected at 550 ppm, with decreases in iron and zinc contents also found. Similarly, Högy et al. 2009, also a FACE study at 550 ppm, found a 7% drop in protein content for wheat, along with decreased amino acid and iron content. Somewhat ironically, this reduction in nutrient content is partially caused by the very increase in growth rates that CO2 encourages in C3 plants, since rapid growth leaves less time for nutrient accumulation.

Increased CO2 has been shown to lead to lower production of certain chemical defense mechanisms in soybeans, making them more vulnerable to pest attack and diseases (Zavala et al. 2008 and Eastburn et al. 2010). Other studies (e.g. Peñuelas and Estiarte 1999) have shown production of phenolics and tannins to increase under enhanced CO2 in some species, as well as many alkaloids (Ziska et al. 2005), all of which may have potential consequences on the health of primary consumers. The decreased nutritional value in combination with increased tannin and phenolic production has been linked to decreased growth rate and conversion efficiency of some herbivores, as well as an increase in their relative demand and consumption of plants (Stiling and Cornelissen 2007).

Furthermore, many “cyanogenic” species—plants which naturally produce cyanide, and which include 60% of all known plant species—have been found to increase their cyanide production in an enhanced CO2 world. This may have a benefit to the plants who use cyanide to inhibit overconsumption by pests and animals, but it may in turn reduce their safety as a food supply for both humans and animals (Gleadow et al., 2009a and Gleadow et al. 2009b).

Interactions with other species

Competing plant species have also been shown to drastically alter expected benefits from excess CO2: even in the best FACE studies, most research still involves artificial experimental plots consisting of fewer than five plant species, and often only one species is present. It has long been understood that due to increased growth of competitor species, benefits from isolated experiments cannot be scaled up to explain how a plant might respond in a monoculture plot (Navas et al. 1999). The distinction is even greater when comparing the behavior of isolated species to those of mixed plots (Poorter and Navas 2003). The lack of correlation (r2 = 0.00) between biomass enhancement (BER) of isolated plants and that of plants in mixed plots is presented in Figure 3.

Figure 3 – Isolated vs. mixed biomass enhancement ratios under excess CO2; From Figure 8 of Poorter and Navas 2003

That some plant species may benefit more fully and/or rapidly from excess CO2 also introduces the possibility that the abundance of certain species in an ecosystem will increase more than that of others, potentially forcing the transformation from one type of ecosystem to another (Poorter and Navas 2003). There is also some evidence suggesting that invasive species and many “weeds” may show relatively higher responses to elevated CO2 (Ziska and George 2004), and become more resistant to conventional herbicides (Ziska et al. 2004, Ziska and Teasdale 2000).

There is some evidence that interacting bacterial communities, particularly in the roots, will be affected through elevated CO2, leading to mixed results on overall plant health. Mutualistic fungal  root communities (known as ‘mycorrhizae') are typically shown to increase under excess CO2, which facilitate nutrient transport to the roots (Treseder 2004), although infections of pathogenic species such as Fusarium (the agent of the disease known as ‘crown rot’) have been shown to become more severe under excess CO2 as well (Melloy et al. 2010).


It has long been known that stomata (the pores through which plants take in CO2 and exhale oxygen and water) tend to be narrower and stay closed longer under enhanced CO2. This effect is often cited as a benefit in that it increases water efficiency in drought situations.

But there is another key piece to reduced stomatal conductance, considering that 90% of a plant’s water use is actually for cooling of the leaves and nothing more: heat from the sun is absorbed by the water in the leaf, then carried out as vapor in the form of latent heat. So while it is true that the plant may retain water better under enhanced CO2, doing so may cause it to retain more heat. This can potentially carry a plant to less optimal temperature ranges (Ball et al. 1988 and Idso et al. 1993). An image present in Long et al. 2006 (Figure 4) shows this effect quite clearly; while a 1.4 C increase is probably not enough to cause significant damage in most cases, global warming will only serve to exacerbate the effect.  It is also of note that the study above represented a well-watered situation, and so during a drought condition the temperature increase would be even higher. 

Figure 4 - Increase in local temperature under enhanced CO2 due to reduced evapotranspiration. From Long et al. 2006

On the cold end, it has been found that for seedlings of some species of evergreen trees, excess CO2 can increase the ice formation temperature on the leaves, thereby increasing their sensitivity to frost damage (Roden et al. 1998).


CO2 is not the only atmospheric gas that is on the rise: concentrations of ground-level ozone (O3) are expected to rise 23% by 2050 due to continuing anthropogenic emissions of precursor gases like methane and nitrous oxides. In addition, Monson et al. 1991 found that natural plant emissions of volatile organic compounds (another group of O3 precursors) increase under excess CO2 in many plant species, thereby introducing the potential that local O3 concentrations around plant communities may rise even higher than the baseline atmospheric level.

O3 has long been known to be toxic to plants: Morgan et al. 2006 found a 20% reduction of soybean yield in a FACE study of 23% excess O3. Similarly, Ainsworth 2008 showed a 14% decrease in rice yield at 62 ppb O3, and Feng et al. 2008 (a meta-analysis of 53 peer-reviewed studies) found on average a 18% decrease in wheat yield at 43 ppb O3. Ozone also appears to reduce the structural integrity of plants as well as make them more vulnerable to certain insect pest varieties such as aphids (Warrington 1988).

Figure 5 - Yield reduction for several crop species under excess ozone. From Wang and Mauzeral 2004

With respect to this effect, excess CO2 may actually prove beneficial in that it causes a narrowing of leaf stomata, thereby reducing the quantity of ozone that can enter the more sensitive internal tissues. Needless to say, the combined effect of excess CO2 and excess O3 is complex, and as it has only recently been given attention it is an area that requires much further research.


A specific plant’s response to excess CO2 is sensitive to a variety of factors, including but not limited to: age, genetic variations, functional types, time of year, atmospheric composition, competing plants, disease and pest opportunities, moisture content, nutrient availability, temperature, and sunlight availability. The continued increase of CO2 will represent a powerful forcing agent for a wide variety of changes critical to the success of many plants, affecting natural ecosystems and with large implications for global food production. The global increase of CO2 is thus a grand biological experiment, with countless complications that make the net effect of this increase very difficult to predict with any appreciable level of detail.

NOTE: This post is also the Advanced rebuttal to "CO2 is plant food".  And a hearty welcome to Dawei to the ranks of Skeptical Science authors

0 0

Printable Version  |  Link to this page


Prev  1  2  3  Next

Comments 51 to 100 out of 106:

  1. david b "... gas exchange analysis of photosynthesis cannot be trusted as it depends on stomatal "openess" to accurately measure the exchange of CO2 and water vapor from the leaf mesophyll and the atmosphere." Gas exchange is certainly problematic if you are studying the short term consequences of water availability on photosynthetic processes. How the the trade off- between CO2 and water economies balance at a physiological level in a world of changing CO2 and climate is a really interesting topic to me. But, I think Bob and I were talking about the influence of a persistent change in local water availability on overall plant growth/biomass/productivity, which is the endpoint of most interest in discussion of the net effect of CO2 and climate change. We don't really need FACE experiments to know water availability makes a difference in regard to vegetative biomass or productivity. The results of large long term natural experiments are there for us to look at right now. I see you answered already...sounds like we're on the same page.
    0 0
  2. Stephen Just to reiterate/clarify, I would bet on the fact that the long term impact of drought and shifting patterns in precipitation will quickly eclipse any benefits realized by atmospheric CO2 "enrichment." Compare a map of Global Net Primary Production (NPP) to a map of global precipitation patterns you'll see a strong relationship between the two variables. Increased CO2 will hypothetically improve water use efficiency but it is clear that precipitation is, far and away, the leading factor determining primary carbon fixation.
    0 0
  3. great post Dawei. but, oh dear, wot adelady says in 23. it's all wiped out by other factors. grown women weeping here at unseasonal infestations of various bugs, despite best efforts of carefully encouraged wild life, slow worms, toads, and even the final solution - blitzing with chickens! a month of drought at a time of normally wet weather can undo any advantage of raised co2 levels.
    0 0
  4. Ian Forrester at 00:41 AM, in the context of the paper you referenced, referring to any differences as being CO2 induced is a means of differentiating the results from the control results. However until the grain and flour properties of the higher yield/ lower protein grains are compared head on head with grains with the same higher yields/ lower protein characteristics grown under non CO2 enriched conditions, then it is not possible to establish whether the differences are merely growth related, or if there is in fact some direct biological link to CO2. Bear in mind that the FACE and laboratory studies are relatively narrow focused, and without the much longer and broader database that has been accumulated by the grain growing and flour milling industries that has seen virtually every combination of factors, apart from CO2, that are possible. The qualities that the paper you referenced focused on as being important, were developed by the industries themselves through the accumulation of knowledge as commercial interests sought to refine the quality and productivity of both the end and the primary products. The battle between yield and protein, and the relevance of nitrogen, is, and has been long and well understood by every grower from even before nitrogen based fertilisers began to be used, and from whom much of the existing knowledge has originated.
    0 0
  5. @Arkadiusz Semczyszak. I see you're being true to form-another long winded post that essentially says *nothing*. "We should also remember that the increase in CO2 usually: - increases the number of leaves and flowers," Actually, CO2 usually increases the vegetative biomass (stems & leaves)-at the *expense* of reproductive biomass (fruits & seeds). Unless you intend to start eating leaves & stems in the near future, I'd suggest that's *not* a good thing. Also, as those leaves will contain less Nitrogen-a major component of the chlorophyll in those leaves-then I'd suggest that this will lead to a decline in total photosynthesis-again in contradiction to the claim that "CO2 is a plant food". "The current "mechanisms" of photosynthesis exist hundreds of millions of years. C4 grasses arose as a reaction to the unusual - in the history of life on Earth - a decrease in the concentration of CO2 - just a 3? million years ago ..." Yes, & guess which kinds of plants are the most dominant in agricultural terms? That's right, the grasses which first evolved 3 million years ago under a "low" CO2 regime. Rice, Wheat, Barley....amongst other "grass-based" crop plants. Again, sort of defeats your argument, doesn't it? "Being (in my country) at an scientific conference on pests - warming - I heard that you get from us (as a result of global warming), The Western Corn Rootworm, Diabrotica virgifera ... I have a question - that the yields and profitability of maize production is higher in my country, or where there is a Western Corn Rootworm ?" ....and what exactly are you trying to even say here? It sounds like a pretty weak attempt to avoid the issue if you ask me. "Consequently, adequate data are not available to reliably estimate the extent to which amelioration of drought stress at elevated [CO2] will improve yields over the range of C4 crop growing conditions and genotypes." Even if this were the case, & I've seen plenty of evidence to the contrary, then at best it simply proves the fact that claims that "CO2 is plant food" is not only overly simplistic, its also extremely premature.
    0 0
  6. "you seem to intimate that root-pathogens, insect pests and other diseases are going to emerge as new problems" @John D. No, what I'm intimating is that these are going to become even *more* dominant problems in an enriched CO2 world-a fact backed up by at least one FACE trial in each of the 3 cases (insect pests, weeds & soil-borne diseases). Even assuming we can overcome these problems quickly enough, it will only be done at a significant increase in the cost of farming-a cost which will be passed on to the consumer. Also, given that the upbeat assessment for yield increases you cite actually seem to all come from just the *one* 3-year FACE trial (Meta-analysis of FACE trials over the last 15 years-most of which were performed under otherwise ideal conditions-shows only a 5-7% yield increase in rice and and 8% yield increase in wheat), I find it slightly hypocritical that you easily dismiss the results of FACE trials which highlight the *downsides* of an enriched CO2 world. Still, I've noticed you've got a habit of cherry-picking only the stuff that supports your claims, whilst ignoring anything which undermines it.
    0 0
  7. @Marcus ”Still, I've noticed you've got a habit of cherry-picking only the stuff that supports your claims, whilst ignoring anything which undermines it.” I only supplement - a very incomplete (in my opinion) this post. Well, because if this post ignores the most positive effects ... I worked 10 years (including: for the Department of Agriculture - the U.S.) on the influence of climate on aphids - and their "enemies” (10 years I taught the students of agriculture, what you should know about: pest control - climate). The most interesting - to my - "paradox" here was that after every cold winter - usually - there were more aphids (unlike the “warm” winter). "Enemies" of aphids, they are simply being reduced more strongly - by frost - during the cold winters - more strongly than aphids. Therefore, in European Climate Change Programme, Working Group II Impacts and Adaptation, Agriculture and Forestry, Sectoral Report, in: Implications of Climate Change on Agriculture - has been positive - it is written: "Reducing the occurrence of certain pests and diseases." I think that despite the passage of years, is still valid position Bubyko of 1998: - “Assessing the importance of expected climate change y its impact on world agriculture, we can conclude that growing anthropogenic global warming and, in particular, the increase in carbon dioxide concentration in the atmosphere can have a favorable effect on crop productivity in many regions of the earth.” (The Close Relationship between Climate and the Global Food Problem, 1998). - “On balance, it is very difficult to conclude with higher accuracy whether the projected global warming would be globally beneficial to human society or not.”(Global Climate Warming and its Consequence. Blue Planet Prize, 1998). However, if we prefer the latest papers ... As was in the past? Europe. It is generally thought that it was mostly dry conditions in warm climates limit the positive effects of increase p.CO2 for photosynthesis - the yield of crops. But let us be careful of such conclusions. The Medieval Climate Anomaly in Europe in simulations with data assimilation, Goosse et al., 2011.: “Evidence for a generally drier climate from ca. 1000-1200 AD is expressed in all compilations. Overall, wetter summers are found during the 13th and 14th centuries, in parallel to the global onset of the LIA, and may have added to the widespread famine in northern/central Europe in that period ...”
    0 0
  8. @ Arkadiusz Semczyszak ....and, as before, you've given us *no* real evidence to back your claims. Where is the proof that famines in the 13th & 14th century were actually caused by climate? They certainly weren't caused by lower levels of CO2-which were at 280ppm throughout that entire time. I'd actually argue that a big part of any famines during that time period might have been the fact that the bulk of the rural labor force had been wiped out by The Black Death-or perhaps you hadn't ever heard of that?
    0 0
  9. "I worked 10 years (including: for the Department of Agriculture - the U.S.) on the influence of climate on aphids - and their "enemies” (10 years I taught the students of agriculture, what you should know about: pest control - climate)." So on the basis of a *single* example, & not a very consistent one at that, you make broad generalizations-how typical of you Ark. Did you factor in the effects of raised CO2 levels as well as temperature? Many studies I've read suggest that breeding cycles of many insect pests will be enhanced by a combination of warmer weather & increased CO2-which would tend to trump your interesting, but hardly convincing, anecdotal "evidence". There is also the FACE study that shows reduced plant resistance to insect predation under eCO2 conditions. I've also read that eCO2 makes herbicides less effective-thus making invasive weeds an even bigger problem in crop management. I've already raised the implications of the results regarding the impacts of eCO2 on soil-borne pathogens. These 3 factors alone (Insect Pest numbers/plant resistance, Weed Numbers/Herbicide Efficacy & soil-borne pathogens) really don't leave your own anecdotal evidence standing up too well-& certainly makes Bubyko's position look very shaky (still, you've proven to have a habit of putting people's unfounded opinions ahead of the bulk of established science). "It is generally thought that it was mostly dry conditions in warm climates limit the positive effects of increase p.CO2 for photosynthesis - the yield of crops. But let us be careful of such conclusions." Why Ark? The two instances are completely different. Any climate change which occurred over the MWP did so over a space of several *hundred* years-& even peak temperatures were not believed to be much higher than they were around the 1970's. What this means is that crops had several hundred years to adapt to what would have been pretty modest changes in climate, whereas current crops need to adjust to climate changes in the space of little more than 100 years, as well as coping with any negative effects of rising CO2 *at the same time*. Also, its worth pointing out that famines were hardly limited to the 13th & 14th century-they also feature in many of the previous centuries, & were not limited strictly to Europe. I suggest you check your facts a bit better in future.
    0 0
  10. Excellent summary. Well done. Keeping in mind some of caveats raised in David B's post at #48, something that is often not touched upon in discussions of this nature is the question "so, do the plants themselves actually want all of this extra carbon dioxide?". One very neat way to answer it is demonstrated by studies that examined the responses of plant stomata density to increasing artmospheric CO2. In Ginkgo biloba*, a tree that has an almost 300 million year history on Earth, it has been demonstrated that stomatal density has decreased by almost 30% since 1924. This would seem to indicate that this species is eschewing at least a large portion of the extra CO2 in order to improve the efficiency of water regulation, and of other thermodynamic costs. It appears that for Ginkgos at least, the response to "more plant food" is to say "thanks, but I'll cash that in for something else, if you please". Ginkgos apparently know of Leibig's law of the Minimum, where global warming deniers do not. [* I mention ginkgos, because their stomatal patterns serve as another proxy for CO2 concentration over geological time...]
    0 0
  11. One of the reasons I often grew impatient with my erstwhile molecular biology (and other biomedical sciences) colleagues was that they frequently displayed a dismaying lack of understanding of ecological, evolutionary, and even thermodynamic limitations to biochemical variation in organisms. Humanityrules at #24 demonstrates exactly this sort of unsophisticated starry-eyed ignorance of the limitations imposed by broader biological issues. Fortunately, Marcus at #38 restored my faith in my molly-bolly brethren by pointing out to HR that there's no such thing as a free lunch. It would be a hijacking of the thread to detail the many ways in which tinkering with evolutionarily-refined characters faces the reality of biological, chemical, and thermodynamic feedings-back, but for folk such as HR I recommend careful consideration of a short piece by Mills and Bonne. Ian Forrester at #45 also makes a salient point by asking for evidence that humans are actually efficent at increasing the efficiency of biochemical processes by tweaking the genetic blueprints of targetted organisms. I await the answer to this with keen interest... For bonus points I would be interested in some clear consideration of how agriculture will function in a world with higher atmospheric CO2, when the oil that fuels the energetic and fertiliser-feedstock requirements for the industry becomes ever more scarce.
    0 0
  12. I'll put up my hand in support of Spaerica's comment at #40 and Stephen Baines' at #47, about precipitation. David B intimates that water availability is more than just precipitation, but I would note explicitly that the related aspect of evapo-transpiration is relevant in this regard too. Even with non-drought conditions, increases in evapo-transpiration rates loom as a big problem for agriculture in the future.
    0 0
  13. I suspect that increased average or maximum temperatures caused by increased atmospheric CO2 content will probably negate any positive effect of CO2 discussed here. I know from experience (200km NW from Sydney, Australia) that during summer heatwaves, when maximum daily temperatures exceed 40C, my vegetables simply stop growing regardless of how much water I can supply. This year our mandarins, a winter crop, started to ripen about three weeks earlier this year. Consequently,they became attacked by Queensland fruit fly (Bactrocera tryoni}, which is a major summer pest here. I can also observe changes in the local rainfall patterns during the last two decades. For example, we are no longer getting major rain events associated with southern cold fronts. Most of our rain now comes from the tropics. These effects may be far more important for plant growth then CO2.
    0 0
  14. Increasing any growth limiting factor is going to increase primary productivity and of course there are going to be resultant winners and losers. Imagine a wetter world, crops like rice would boom while dryland crops like wheat would fall prey to fungal attack. A similar scenario would happen with CO2 for other species but undoubtedly there will be more winners. Sorry, this article is grasping at straws, if you (AGW community) want to spar with the sceptics find an argument with a lot more uncertainty like CO2 and climate.
    0 0
  15. DVB. You obviously haven't comprehended the explanations of the ecophysiological responses of plants such as rice, or the implication of temperature increase in the future. The whole point of this thread is that many of the "winners" are likely not to be of human benefit, and many of the "losers" will be profound in their loss to humans. Your comment about rice explicitly demonstrates that you know not about what you speak. If you disagree with this assessment, you will of course be able to support your statement that "undoubtedly there will be more winners" with actual peer-reviewed science. Your time starts now.
    0 0
  16. DLB said:
    Imagine a wetter world, crops like rice would boom
    Unfortunately, a warmer climate will reduce rice yields. Rice is particularly susceptible to a rise in minimum temperatures, which is what happens with AGW i.e. minimum temperatures will rise faster than maximum temperatures:
    Grain yield declined by 10% for each 1°C increase in growing-season minimum temperature in the dry season, whereas the effect of maximum temperature on crop yield was insignificant. This report provides a direct evidence of decreased rice yields from increased nighttime temperature associated with global warming.
    This is why it is much better to actually see what the science tells us rather than making predictions based on the hope that CO2 pollution will result in positive effects.
    0 0
  17. The only ones grasping at straws here, DLB, are you & your fellow Contrarians. You're all so desperate for there to be some "silver lining" attached to rising CO2 emissions that you're blindly grasping at an incredibly poor understanding of High School Biology. We've already highlighted here that plant growth will-ultimately-be limited by factors *other* than CO2, & that rising CO2 emissions will have several highly detrimental impacts on crops even *before* we consider the effects of climate.
    0 0
  18. Ian Forrester at 12:29 PM, whilst the paper you referenced studied the relationship between the maximum and minimum temperatures, as well as measured solar radiation, to rice yields, it also allows comparison to be made between how solar radiation over the trial period, which steadily increased from about 15.5MJ/m2/day to about 18MJ/m2/day, correlates closer with the minimum temperatures than the maximum. What do you think the connection is and what mechanism might link the increasing solar radiation to the rice yields given the physiological mechanisms that might link any decrease in yields and the night temperatures are unknown. One thing I feel the study has missed including is cloud cover given clouds are most relevant the radiating off of heat at night. Not having data regarding cloud coverage means yet another assumption has to be made.
    0 0
  19. HR: I'm not here to paint utopian visions just to counter unnecessary pessimism. Acknowledging the full seriousness of AGW, and believing that we can take intelligent steps to address it, is optimism. Denying that AGW exists is wishful thinking, at best. Believing that the people who are best equipped to understand AGW are liars, incompetents or dupes is pessimism. Your stance seems to me to be a combination of wishful thinking and pessimism. Human ingenuity is incredibly powerful, but it works best when people pull their heads out of the sand and face facts.
    0 0
  20. "I worked 10 years (including: for the Department of Agriculture - the U.S.) on the influence of climate on aphids - and their "enemies” (10 years I taught the students of agriculture, what you should know about: pest control - climate). The most interesting - to my - "paradox" here was that after every cold winter - usually - there were more aphids (unlike the “warm” winter). "Enemies" of aphids, they are simply being reduced more strongly - by frost - during the cold winters - more strongly than aphids." Interesting that you neglect to note the fact that warm winter temperatures are also beneficial to aphid phenology (see e.g. Zhou et al (1995) Global Change Biology; Bale et al (2002) ibid; Harrington et al (2007) ibid). From the first of those references: "...A 1 °C increase in average winter temperature advanced the migration phenology by 4–19 days depending on species...". From the second: "...even with global warming the threshold temperatures for ¯ight are rarely exceeded and apterous aphids are more fecund than alatae. Anholocyclic aphids, unlike the overwintering eggs of holocyclic species, do not have a winter diapausing stage and are not required to pass through one or more wingless generations on the winter host prior to host alternation. The former can therefore colonize crops more quickly when spring conditions become favourable..." From the third: "...The extent to which any changes in aphid phenology will translate into changes in the pest status of aphids will depend partly on how the phenologies of their crop hosts change. In the case of annual spring planted crops, planting dates depend greatly on soil condition in spring, and this is affected particularly by winter and spring rainfall, less so by temperature. With aphids, it is probably the other way around. There is much more uncertainty over future patterns of rainfall than there is over temperature, and it is hence difficult to predict how crop phenology will change. In the case of potatoes and sugar beet in the United Kingdom, unpublished data suggest that planting dates are not advancing as fast as aphid first flight dates. If this is the case, aphids may arrive when crops are at an earlier and more susceptible growth stage..." Takehome message - Arkadiusz should know this research if he has worked on aphids for as long as he claims. The final sentence of the final paper I reference is the clincher - "aphids may arrive when crops are at an earlier and more susceptible growth stage". As Arkadiusz should know there is a lag between aphid arrival in crops and their detection by predators it is this period that is most important to the effect of aphid pests on the crops, as virus transmission and feeding damage will occur then. It is known that if aphids are particularly abundant in the early season then they are less so later on in the year (due to predator action - and the opposite is also true, if aphids are less common in the early season predators are less successful and there is a flush of late aphids at the end of the season) but it is in the early stages of crop development that virus transmission and feeding damage are most important.
    0 0
  21. Apologies for the poor formatting above - copying & pasting from a pdf is fraught with danger!
    0 0
  22. It seems the evidence indicates that climate change is already negatively impacting global cereal crop years in the period 1980 to the present. The paper published in Science yesterday is behind a paywall, but Scientific American has a summary here.
    0 0
  23. chris at 18:51 PM, it's hardly up to the present time given the study period was only until 2008. Also considering the study supposedly focuses on Global grain production of the four major grains, wheat, maize, rice and soybeans, there are several major provisos that has to be taken into account, apart from the fact it is all based on modeling trying to tie production directly to temperature. Firstly the positive and negative impacts on rice and soybeans apparently balances out, so nothing there. Then America is noted as an exception as yields there and several other places have instead risen as indicated by the rather unscientific map accompanying the Scientific American article that fails to include Australia, making the global climate change impact on global cereal crops somewhat less than global in nature. One is then left wondering how the periodic overproduction of grains in the study period were accounted for. All this finally seems to fly in the face of the fact that nearly 3 times as much cereal grain is presently being produced from the same acreage as 50 years ago, and agricultural analysts believe that this can be repeated over the next 50 years.
    0 0
  24. Hi Chris @72, Just saw that paper. "We can see how much these variables affect crops... for example, for a crop like wheat, a degree (Celsius) of warming on a global average translates to about a 5% loss in production." And people are still trying to argue that AGW associated with doubling of CO2, and the associated warming and shifts in precipitation are not going to be an issue. Well, here we have evidence that agriculture is already being negatively affected. We are in the coal mine, the canary is sick, and some choose to think of every reason under the sun why it is not an issue, and that there is no reason to take preventative, prudent action.
    0 0
  25. I believe this quote:
    "considering that 90% of a plant’s water use is actually for cooling of the leaves and nothing more"
    is not correct so I will search for peer reviewed literature to back up my statement. Remember that plants are solar-powered. (Simplified chart: photosynthesis-chloroplast.jpg ) The first stage of photosynthesis involves the photolysis of water which produces three things: a free electron to power chemical reactions via ATP, O2 which is discarded (this is the only place where oxygen is released), and a charged hydrogen atom. People wishing to "quickly" learn more about the details of photosynthesis should start with these videos: Now it is true that plants lose water through their stoma, but as temperature rises, the stoma begin to close and photosynthesis is reduced. (most c3 plants are are 100% open at 24.4C and 100% closed at 30C). If the primary purpose of water was cooling, the plants would release it all to save themselves. In fact, they close off their stomas to limit water loss because water will be needed (photolysis) as soon as the temperature drops and the stomas open.
    0 0
  26. John Nielsen-Gammon has thrown down the gauntlet! ( He says that "Some things about carbon dioxide in the climate system are so firmly established and fundamentally important, you can use them as litmus tests to determine whether the person you are listening to is honest and knowledgeable." Fact #3 in his list is "Carbon dioxide is good for plants, in the sense that it makes them grow more rapidly. If you hear or read somewhere that man’s addition of CO2 to the atmosphere has been generally harmful to plant productivity, your source is either too naive to know better or trying to deceive you. He says of this site: "Unfortunately they can't bring themselves to admit that the evidence, while complex, does point to a net overall benefit to plant growth for the next few decades" Is Skeptical Science ignorant, [-snip-] or has JNG overstated his case? I very much respect both the Skeptical Science team and JNG. I look forward to seeing this apparent disagreement reconciled. P.S. possibility #4 is that it is me who is overstating his case, however he says that he "had looked at the (skeptical science) site" - presumably before writing the piece. So while the statements aren't targeting SS directly, SS had at least been considered. P.P.S. Interestingly JNG is typically very conservative with statements regarding what the science can tell us. Skeptical Science on the other hand is often addressing the "We don't know everything therefor we know nothing" crowd. In this case the roles appear reversed.
    0 0
    Moderator Response: [JH] The correct acronym for Skeptical Science is "SkS".
  27. lazej#76: Curious that you omit Fact #1: A small concentration of CO2 is a big deal. and Fact #2: The fraction of CO2 molecules in the atmosphere that were produced by man is different from the fraction of CO2 molecules in the atmosphere that are there because of man. He goes on to say that man-made CO2 is indeed causing warming. Both of these are part of the same litmus test. If you hear or read somewhere that the amount of carbon dioxide in the atmosphere is so small that it must be unimportant, your source is either too naive to know better or trying to deceive you. ... If you hear or read somewhere that the amount of man-produced CO2 in the atmosphere is only a small fraction of the total CO2 in the atmosphere and that therefore man is having a small effect, your source is either too naive to know better or trying to deceive you. Further comments on JNG's post take issue with his dismissal of SkS' argument.
    0 0
  28. Layzej: You have come to the right place for answers. All you need to do is read the opening post for the thread you have posted on and you will find Skeptical Sciences response to your question. If you have any more questions after you have read the opening post feel free to post them.
    0 0
  29. Layzej - John NG needs to bone up on the latest research. No one is suggesting that increased levels of CO2 won't benefit plant growth - all things being equal. But that's just it, they are not equal, and recent studies find little evidence for it on a global scale. We (SkS) know that the carbon cycle models used in the last IPCC (2007) report expect a CO2 fertilization effect, a huuuuge CO2 fertilization effect. But isn't it interesting that previous work on historic forest growth in North America over the last few centuries found no evidence for it? The latest global forest inventories show that the uptake of CO2 by land plants is occurring because of forest re-growth, (forests chopped down and allowed to grow back) not because plants are lapping up the extra CO2. The prime areas of reforestation are in the former Soviet Union, China and in the tropics. On a global level there seems to be little evidence of the CO2 fertilization effect. This makes perfect sense, re-growth areas can chew through a fair amount of CO2 as they grow into mature forests and incorporate the extra CO2 into plant mass, but mature forests have a limited capacity for further growth. " I had looked at the site...unfortunately they can't bring themselves to admit that the evidence, while complex, does point to a net overall benefit to plant growth for the next few decades." Or perhaps the correct answer is that John Nielsen-Gammon is conflating forest re-growth (areas where forest has been allowed to re-establish) with the CO2 fertilization effect. I get the impression he can't be bothered accurately researching this topic. Maybe he needs to consult Stephen Pacala? As far as the consequences for human agriculture - which is the subject of Dawei's post, that doesn't look too flash either. Many human crop foods will be negatively impacted by rising temperatures and drought over the next few decades, including main staples such as corn and rice. And what about ocean acidification? Global warming's evil twin? Dude, there are many reasons to limit CO2 emissions, focusing on one tiny detail blinds one to the 'big picture.'
    0 0
  30. Layzej @76, among the interesting things John N-G writes is:
    "As long as the climate effects are small, they don’t matter much, but to the extent that climate changes faster than plants can move around to keep up with it, climate change will be bad for native plants. Worse, in the tropics, the climate may change into something with no existing analogue on Earth and thus no pre-adapted species ready to move in. Computer models with an interactive biosphere generally agree that incremental increases of CO2 help plants overall, and most say that the global ecosystem will continue to gain biomass through 2100. In other words, the better growing conditions due to more CO2 outweigh adverse conditions due to the changing climate for the foreseeable future. The crossover point, where net global growth is actually inhibited by the combination of CO2 fertilization and resulting climate change, is poretty much the most poorly known number relevant to climate policy. Certainly as the climate changes there are concerns about the extinction of species and the loss of the ability to grow adequate crops in some areas. But in the meantime, as long as one is not concerned about the fate of individual vulnerable species, CO2-induced climate change is a net positive for plant growth. This is true based on the most basic numbers of the man-altered carbon budget."
    By my reading, that is in complete agreement with the more detailed discussion above. His objection to this post seem to come down completely to the absence of a sentence saying that despite these grave concerns, for the future, there will be a short term (20) year benefit for plants in general, although not necessarily for crops. Given the turn around time of climate change policy, and the even longer turn around time for any action to start reducing growth in global temperatures, I do not think pointing out a possible short term benefit is either necessary or helpful. Still less so as it is not certain that that short term benefit exists. As noted by Steve Bloom in comments at John N-G's blog, his method of estimating the benefit to plants is indirect, and necessarily includes aquatic as well as land plants. More generally it potentially shows in increase in plant life, not in human agricultural productivity. It is of scant benefit to us if over the coming decades Net Primary Productivity (ie, the total global growth of plant life) increases if that increase is in the form of algal blooms and weeds. Further, I say talk of a potential increase, as even John N-G mentions a possible mechanism whereby the observations of increased carbon take up are compatible with decrease plant growth, ie, a larger decrease in plant decomposition. Although he dismisses that possibility, a recent study (whose title and authors I can't remember unfortunately) showed that production of oil and coal generating strata peak in periods of high CO2 content. Production of fossil fuels requires the burial of organic carbon without decomposition, so that study suggests that high CO2 content may indeed lead to reduced rates of decomposition, primarily by promoting anoxic conditions in warm waters. It seems to me that John N-G would have done well to read the title above. "If only it were that simple". Because of that complexity, Dawei's conclusion was, "The global increase of CO2 is thus a grand biological experiment, with countless complications that make the net effect of this increase very difficult to predict with any appreciable level of detail." That is, he has neither endorsed claims of benefit or of harm to plants from CO2, but merely drawn attention to some of the many complicating factors. In the end, difference between his and SkS's discussion of the topic is that we did not rush to a simplistic conclusion.
    0 0
  31. Rob: There is no question that CO2 enhances plant growth. This is documented in this Wisonsin Study. Tree growth with elevated CO2 As far as temperature, the temperature, at least in the main corn growing areas of the USA would have to elevate by over 4.0C to be a growth hinderance. This would have to occur at precise times as well, as corn is sensative to higher temperatures for approx 2 weeks time in the growing season. Outside of the pollination and early fill window, higher temperatures help with the conversion to starch in the ear and can allow greater kernal depth. This is benificial. However, the lowering of PH of the oceans as a result of higher levels of CO2 is a huge concern. The lower PH benfits some crustaceans, but in my humble opinion, the overall benifits do not outweigh the potential negatives. Woods Hole Study of PH
    0 0
  32. Tom@80: Elevated CO2 benifits C3 and C4 structured plants. All cereal grains are grasses, so this study has a very strong relation to wheat/corn/ etc. NASA study on C3 and C4 grasses with elevated levels of CO2 It is also well known that enhanced CO2 promotes larger "root balls". Because of this, the plant is more efficient at using the available nutrients/water in the soil. With enhanced levels of CO2 there are indications that farmers will be able to reduce the N input and achieve the same yield. This would allow 3rd world countries to increase the mass of their food production. From a plant perspective, higher CO2 is good. Most plants evolved when CO2 was higher on earth and have not seemed to have lost that desire. But, even with enhanced bio-mass, the lowered PH of the oceans is a mighty concern that MUST be taken into account in the balance.
    0 0
  33. Camburn @82, I know you enjoy looking at a very carefully selected quarter of the picture. Just don't expect us to be mislead by your propensity. In other words, read the main post. If you can't rebut the points it raises, you have nothing worth saying.
    0 0
  34. Camburn - you are misinterpreting what I wrote. Young forests, which are not nutrient-limited in some other way, can indeed benefit enormously from more CO2. The FACE trials indicate that mature forests don't - there's only so big trees can grow and therefore a limited capacity to soak up CO2. Young forests on the other hand have a large capacity for growth and drawdown of CO2. It makes perfect sense. In the real world, however, many areas are nutrient-limited - phosphorus, nitrogen and especially water. That's perhaps why the CO2 fertilization effect (a global increase in plant biomass due to more CO2) has not been found. All the extra CO2 seems to be going into forest re-growth. This tallies with global estimates of growth in pastural coverage- they have plateaued in recent decades. As far as corn is concerned, that too is under threat see SkS post: Maize harvest to shrink under Global Warming - based on Lobell (2011)
    0 0
  35. Tom@83: I am in production agriculture Tom. The "quarter" I am most interested in is feeding people. As most of the worlds food stocks are annual in nature and derived from grasses, the area of research most intersting is the responses to co2, etc. The types of plants that feed the world have repeatedly demonstrated increased productivity from higher levels of CO2. Rob@84: I will have to re-read Lobell (2011). There were problems with that study that a farm paper talked about. When I have time to read it and reference it, I will comment on said link. Thank you for the Link.
    0 0
  36. 85, Camburn,
    The types of plants that feed the world have repeatedly demonstrated increased productivity from higher levels of CO2.
    Do they similarly react well to increased temperatures, increased or decreased moisture, and more volatile precipitation and temperature patterns? Do they demonstrate an unending improvement for higher and higher levels of CO2, without limit or eventual negative result? Are you in a business where you can afford to simplistically look at and focus on a single variable, with complete disregard for other factors?
    0 0
  37. muoncounter @77, Fact 1 and 2 are off topic on this thread and moreover not areas where JNG has suggested that SkS has fallen down. Michael sweet @78, I'm not sure what you are getting at. The JNG post was written after considering this very SkS post and finding it wanting. Rob @79, No doubt there are many reasons to reduce CO2, however JNG has suggested that this particular item is a litmus test to determine whether the person you are listening to is honest and knowledgeable. A bold statement and one that I am grateful to see addressed by you and the S(k!)S team. Tom Curtis @80, thanks for the thoughtful and thorough response! Your points are all well taken, although I'm not sure it's a good idea to consider policy turn around time when writing a post. I would like to think of SkS as a place that cuts through all the BS and provides the facts - warts and all.
    0 0
    Moderator Response: [JH] The auditions for SkS Moderator candidates were held last week.
  38. Sphaerica@86: 1. It is established that cereal plants respond well to increased CO2. 2. It has also been established by root studies that plants develop larger root mass with the presence of CO2. 3. By having larger root balls/mass the plant has a larger structure to overcome normal potential weather variations. 4. You indicate more volatile precip and temperature patterns. I don't know if you can get much more volatile than the climate I live in. An old saying in the upper plains of the USA is "If you don't like the weather right now, wait 5 mins and it will change." The higher levels of CO2 that increase plant mass that I have read are up to approx 850ppmv. What happens after that, I don't know. The studies done by the Ag community reflect the potential levels that "may" be obtained. The element of risk in production ag is so large, that a small addition of a potential benifit is viewed positively. The upper plains of the USA, and I live very near the 49th parallal. One of the areas that is suppose to be most affected by climate change. At this point and time, there has not been any variation from the long term norms of just right, to too wet, to too dry. From too cold, frost in 2005 in August, to to warm.....that hasn't happened since 1988. I read studies of anything pertaining to production ag with a very critical mind. A small change can be the difference between being profitable, and going broke. And worst of all, not having a crop, as my desire is to feed people. Warmth in my area is benificial to production as most of the time we are on the edge of being too cold. Precip patterns are within the boundaries of a 80 year wet/dry cycle in the Central Corridor of the USA that is part of a longer 400 year cycle: 400 year cycle of precipitation of Great Plains of NA Shorter cycle within the longer cycle:
    0 0
  39. Camburn, "it is established" requires real substantiation, put up the references. This statement leaves a lot to be desired: "By having larger root balls/mass the plant has a larger structure to overcome normal potential weather variations." Provide references to studies showing that it actually does allow them to overcome. Without it, this is nothing but wishful thinking. When they were trying to break the sound barrier, engineers though that a generously reinforced structure would enable a onventional airplane to go there and back safely. It wasn't quite so. If you're so worried about going broke you need to adress the factors that make prices so volatile. They belong with the banks and the speculators trying to profit from commodities markets, good luck going after that. I live in the 40's latitudes too and I was battling mosquitoes on my outing to the falls today with the kids. Never seen them yet in this place at this time of the year. If you are in a place that already was on a Northern margin, then probably you're safe, and warmth in your area is indeed beneficial. I'm sure the ones who live closer to the Southern margin have a different take. Of course, if we stick purely to the capitalistic risk/benefit analysis, in your individual case you're not supposed to personally give a dam* about the problems of farmers who live in other places. In fact, the more they suffer, the better you're likely to make out: production decreased on their part, increased on yours, if the overall production is down, you'll really make a killing without having to do anything special. More power to you I guess.
    0 0
  40. Layzej @80, the time frame considered in the response is just the next century, and as such is determined by "skeptical argument" it is rebutting. Where the so-called skeptics nuanced enough to argue that in the sort term, net benefit to agriculture from global warming is positive, but in the medium term it is uncertain, and in the long term under BAU it will be significantly negative in most areas, and negative overall globally, I'm sure the response would have discussed the different effects over different time periods - and largely agreed with them. I'll also note that had the myth it is rebutting been more geographically nuance, I'm sure some of the geographical nuances would also been reported. One of those is the fact Camburn is benefiting from, ie, that the Northern USA and Canada will probably get higher yields for some time to come (possibly for the next century even with BAU). Unfortunately their good fortune in that respect does not generalize to the rest of the world.
    0 0
  41. layzej @87 - Well, I'll just stick to the CO2 fertilization effect, and ignore all that utterly dire stuff about ocean acidification then. First up let's be clear, the argument that John Nielsen-Gammon makes is that extra CO2 will be beneficial in the next few decades. To test that we need to look at what the observations reveal. Again, I point out that we (SkS) don't dispute that CO2 fertilization is a real phenomenon, but the point is, will this effect be enough to counter the negative effects of a warmer and perhaps drier (for many regions) world? We know that the carbon cycle models used in the last IPCC assessment report expect this CO2 fertilization effect to be huge in the 21st century. Those models simulate a dramatic draw-down of atmospheric CO2 by land vegetation. But they also assume no nutrient limitation - which seems a glaring omission. - no evidence of CO2 fertilization leading to increased biomass in a Thai tropical forest: - Long-term increases in intrinsic water-use efficiency do not lead to increased stem growth in a tropical monsoon forest in western Thailand - Nock (2011) - no CO2 fertilization net benefit in a Costa Rican rainforest - Annual wood production in a tropical rain forest in NE Costa Rica linked to climatic variation but not to increasing CO2 - Clark (2010) - no CO2 fertilization net benefit in a Canadian forest - Testing for a CO2 fertilization effect on growth of Canadian boreal forests - Girardin (2011) - and crucially, no global CO2 fertilization effect net benefit in the last 40 years - increased water-use efficiency during the 20th century did not translate into enhanced tree growth - Peñuelas (2011) they write: "Location A global range of sites covering all major forest biome types. Main conclusions These results show that despite an increase in atmospheric CO2 concentrations of over 50 p.p.m. and a 20.5% increase in iWUE (intrinsic water-use efficiency) during the last 40 years, tree growth has not increased as expected, suggesting that other factors have overridden the potential growth benefits of a CO2-rich world in many sites. Such factors could include climate change (particularly drought), nutrient limitation and/or physiological long-term acclimation to elevated CO2. Hence, the rate of biomass carbon sequestration in tropical, arid, mediterranean, wet temperate and boreal ecosystems may not increase with increasing atmospheric CO2 concentrations as is often implied by biospheric models and short-term elevated CO2 experiments." And the real clincher is that the tropical regions, despite the huge deforestation occurring there, are actually by far the largest land-based carbon sink, and they happen to be the most threatened, because tropical trees most likely exist near a thermal tolerance threshold. This meme by John NG is extremely disappointing coming from a climate scientist who should know better. But to adequately de-bunk it (yes, there is a great deal more peer-reviewed science to debunk it) requires perhaps a two or three-part blog post/rebuttal. I've added it to my to-do list.
    0 0
  42. Thanks all! It will be interesting to see where the IPCC AR5 (with newer studies considered) will fall on this issue.
    0 0
  43. Of the three positions, I'm inclined to trust Tom Curtis, whose position seems more nuanced, over Rob Painting or John Nielson-Gammon. I'll use IPCC AR5 as the final arbiter. It would be ironic if JNG ends up failing his own litmus test ;)
    0 0
  44. layzej @93, I appreciate that you think I am more nuanced, but on this topic Rob Painting is certainly better informed than I am, and I suspect also than John N-G is. He has certainly found some research which counters John N-G on the short term impacts of CO2 rise along with global warming on land plants. My point has been that John N-G was not justified in his criticisms of the blog post above. Indeed, it is not even relevant in that it missed the point of the post, which does not discuss time frames per se. On the other hand his point may be relevant regarding Rob's prospective three part blog (which I am looking forward to). I doubt, however, that it will be justified.
    0 0
  45. There are two areas of study being developed here. 1. Established forests and the effects of CO2. 2. Short lived biota. I will have to read Rob's links concerning established forests as this is an area that I have not studied. Item 2: Higher levels of CO2 are benificial for short lived biota growth. This has been demonstrated in the links provided. Short lived biota produce the bulk of grains etc that support man's diet.
    0 0
  46. Camburn, You are kidding yourself by putting undo weight on what you like (CO2 is plant food) and ignoring what you don't like (temperature and precipitation variations that could more than destroy any benefits that might be derived from higher CO2 levels). Sadly, given your personal approach to the problem, you are going to have to take personal blame for your predicament if the practice of agriculture gets rough in your region in the coming decades (unless, of course, you've retired by then and sold your farm to some sucker). Climate change is not a variation on Chicken Little. It is instead a worldwide version of the Grasshopper and the Ants fable. In this case, though, the Grasshoppers don't mind working, they just don't want to adjust how they work and pay closer attention to the coming "winter."
    0 0
  47. 97, Camburn, Actually, if you're in ND, you may well be one of the few that benefits from climate change. The net loss will be huge, but you could be raking it in due to a combination of better productivity coupled with rising prices because of the desolation in the Southern USA.
    0 0
  48. Sphaerica: When I see credible projections that the Southern USA is going become a desolate area, I will take that into consideration. And when I see credible projections concerning the actual response to increased CO2, other than oceans, I will also take that into consideration. As I have stated, the potential lowering of PH is a HUGE concern. I live my life as low in carbon emissions as economically possible. I understand very well the economic dynamics of the current period. They are starting to be played out in Greece, Italy, Spain, Portugal, France, UK, USA. The result of government spending with no return of value has/will doom the changes required as the money is not there to do so. It has already been spent/consumed by government.
    0 0
  49. 98, Camburn, Not "desolate." That's an unnecessary exaggeration. There are credible projections that climate change will result in reduced precipitation in the Southern US, and the Mediterranean, and other regions. You should be a little less cavalier about what does and does not concern you.
    I live my life as low in carbon emissions...
    And yet you come to this site and post comment after comment encouraging people to ignore the science behind climate change, and as a result to continue living their lives the way they always have, fraught with waste and ill-advised/unnecessarily-wasteful practices.
    The result of government spending with no return of value...
    That's an unnecessary foray into politics on which I will pass. Certainly budgets must be reigned in because we live on a planet that is living beyond its means in a lot of different ways. Finding the right areas to cut is the issue, but it's also politics that is OT here.
    0 0
  50. Sphaerica@99: "And yet you come to this site and post comment after comment encouraging people to ignore the science behind climate change, and as a result to continue living their lives the way they always have, fraught with waste and ill-advised/unnecessarily-wasteful practices." I don't post with the idea of encouraging people to ignore climate science. I post with the idea of increasing people's knowledge and perspective concerning climate, and the science. I agree, pass on the government spending/economics. It does however, play a role in the economic dynamics of achieving meaningful adaptation.
    0 0

Prev  1  2  3  Next

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

The Consensus Project Website


(free to republish)

© Copyright 2021 John Cook
Home | Links | Translations | About Us | Privacy | Contact Us