What about all the people who say the world will be greener and therefore there will be more plants and food? It's almost like they just made that up to suit their worldview?
The world will become unevenly greener. Population density and recent population rise is inversely correlated with places that will get greener.
Polar and Continental regions will get greener at the expense of the tropical and equatorial regions.
Mass migration is the inevitable conclusion of uneven impacts of climate change. Ie. In 2026, Political climate and physical climate are moving in mutually incompatible directions.
The greening is uneven. Canada/Siberia are getting warmer so plants have longer growing seasons there. But it's getting browner in other areas because of increased drought and heat. Overall the predictions are for lower global food production on net.
The world will be greener in a high-CO2 environment. There’s no legitimate argument over that fact.
Where you go wrong is in misrepresenting the argument as “more plants and food”. That’s a straw man. Certainly it’s more favorable for growth of plants that make food, but that doesn’t mean that existing patterns of food production will exist unchanged, or that adaptation won’t be required. But we’re also talking about a 100+ year change timeline. People who tell you that this year’s weather are indicative of urgent, rapid change are exaggerating.
You seem to be willing to accept wild extrapolations of doom without evidence, while rejecting scientifically well-founded statements of fact, so I’d challenge you to examine your priors.
> The world will be greener in a high-CO2 environment. There’s no legitimate argument over that fact.
However it's important to remember that world isn't a high school physics experiment, and you can't easily separate out CO2 concentration from the other impacts of increased CO2:
| Climate change can prolong the plant growing season and expand the areas suitable for crop planting, as well as promote crop photosynthesis thanks to increased atmospheric carbon dioxide concentrations. However, an excessive carbon dioxide concentration in the atmosphere may lead to unbalanced nutrient absorption in crops and hinder photosynthesis, respiration, and transpiration, thus affecting crop yields. Irregular precipitation patterns and extreme weather events such as droughts and floods can lead to hypoxia and nutrient loss in the plant roots. An increase in the frequency of extreme weather events directly damages plants and expands the range of diseases and pests. In addition, climate change will also affect soil moisture content, temperature, microbial activity, nutrient cycling, and quality, thus affecting plant growth.
> Certainly it’s more favorable for growth of plants that make food
That does not seem to be what agricultural researchers believe:
| In wheat a mean daily temperature of 35°C caused total failure of the plant, while exposure to short episodes (2–5 days) of HS (>24°C) at the reproductive stage (start of flowering) resulted in substantial damage to floret fertility leading to an estimated 6.0 ± 2.9% loss in global yield with each degree-Celsius (°C) increase in temperature
| Although it might be argued that the ‘fertilization effect’ of increasing CO2 concentration may benefit crop biomass thus raising the possibility of an increased food production, emerging evidence has demonstrated a reduction in crop yield if increased CO2 is combined with high temperature and/or water scarcity, making a net increase in crop productivity unlikely
| When the combination of drought and heatwave is considered, production losses considering cereals including wheat (−11.3%), barley (−12.1%) and maize (−12.5%), and for non-cereals: oil crops (−8.4%), olives (−6.2%), vegetables (−3.5%), roots and tubers (−4.5%), sugar beet (−8.8%), among others
> you can't easily separate out CO2 concentration from the other impacts of increased CO2
>> I never said you could?
I took the fact that you explicitly mentioned "high-CO2 environment" and claimed there was no room for argument over the "fact"s as an indication that you were trying to separate out the impact of CO2 from other factors caused by climate change such as heat stress and drought. If that wasn't the case then apologies for misunderstanding.
> That paper is talking about a net reduction in biomass due to projected losses in places with temperature increases exceeding 10 degrees C.
The abstract says:
| with great biomass reductions in regions where mean annual temperatures exceeded 10 °C
Unless the abstract is especially badly written that suggests that it's not 10°C _change_ but 2°C change leading to biomass loss in areas that are already at 10°C on average.
> IPCC report
Thanks, that's a useful reference! Do you have a link to the final report? That one seems to be a draft and I didn't find the right published version (but there are many so I'm sure I'm missing it).
I note the paragraph you quoted concludes:
> The increased greening is largely consistent with CO2 fertilization at the global scale, with other changes being noteworthy at the regional level (Piao et al., 2020); examples include agricultural intensification in China and India (Chen et al., 2019; Gao et al., 2019) and temperature increases in the northern high latitudes (Kong et al., 2017; Keenan and Riley, 2018) and in other areas such as the Loess Plateau in central China (Wang et al., 2018). Notably, some areas (such as parts of Amazonia, central Asia, and the Congo basin) have experienced browning (i.e., decreases in green leaf area and/or mass) (Anderson et al., 2019; Gottschalk et al., 2016; Hoogakker et al., 2015). Because rates of browning have exceeded rates of greening in some regions since the late 1990s, the increase in global greening has been somewhat slower in the last two decades
So it sounds like a combination of the CO2 increases up to about the year 2000, along with agricultural intensification and various other factors have indeed increased the amount of plant cover, but we are already seeing changes to that picture with further rises to CO2 levels.
> You spent a lot of words arguing with me about things I didn't say.
Well you started with
> The world will be greener in a high-CO2 environment. There’s no legitimate argument over that fact.
And my central point is that the model you're implying there is one in which there's a monotonic relationship between CO2 levels and plant growth. However in reality things are clearly more complex than that, and there is indeed legitimate argument over what factors are dominant in different scenarios.
Your claim that things will only change over long-enough timescales so that you don't have to worry about also seems to lack evidence. In systems with significant feedback loops it seems dangerous to assume that changes will only happen slowly unless you're very confident that you fully understand all the system dynamics. With climate change it's clear that we don't fully understand the system, and some changes are happening faster than earlier models predicted. So _maybe_ we have a few centuries to figure out how to move global agriculture to northern latitudes, and deal with more variable conditions, but from a risk-analysis point of view it seems like a rather poor strategy.
The conclusion is the same, though they've added a paragraph talking about browning in some areas "somewhat slowing" the rate of aggregate increase since the late 90s. Conclusion is unchanged, and in fact, they strengthened it versus the draft by directly attributing it to CO2:
"The increased greening is largely consistent with CO2 fertilization at the global scale, with other changes being noteworthy at the regional level (Piao et al., 2020)"
> So it sounds like a combination of the CO2 increases up to about the year 2000, along with agricultural intensification and various other factors have indeed increased the amount of plant cover, but we are already seeing changes to that picture with further rises to CO2 levels.
Not really. The observations are also made in uninhabited areas. See above.
> And my central point is that the model you're implying there is one in which there's a monotonic relationship between CO2 levels and plant growth.
I said nothing about a monotonic relationship. I said that the earth will have more plants (plant mass, really) with more CO2. This is inevitable. It could follow a monotonic relationship, or it could do something else as factors shift. For example, one big, unpredictable factor that likely swamps everything else, is the randomness of human behavior.
> However in reality things are clearly more complex than that, and there is indeed legitimate argument over what factors are dominant in different scenarios.
No. Greening is occurring, and has been for some time. We have multiple lines of evidence. The IPCC report confidence is high. The only debate is over what might happen in the future, which, again, is fortune telling -- involving not only the climate system, but the actions of people.
> In systems with significant feedback loops it seems dangerous to assume that changes will only happen slowly unless you're very confident that you fully understand all the system dynamics.
I grant you that one can imagine theoretical scenarios in which all sorts of doomy feedback loops happen. The problem with that kind of imaginative exercise is that you have to bring evidence of their existence. So far, with regard to global vegetation, no such evidence exists, and in fact, the opposite of the doom loop scenario is occurring.
Could this change? Maybe! But that's just storytelling right now.
You made a scale-free claim about increasing greenness with increasing CO2 concentration. That implies a monotonic relationship.
> The only debate is over what might happen in the future, which, again, is fortune telling
The idea that using models of physical systems to predict their future evolution is "fortune telling" will surprise many scientists. Indeed, you yourself have proposed a simple model and used it to make a prediction about the future ("the world will be greener in a high-CO2 environment"), and used linear extrapolation of the past to justify the adequacy of your model.
That's not necessarily a bad starting point, but when actual studies with more complex models show different behaviours you should consider there's a possibility you're over-confident in your predictions.
Anyway, I suspect this conversation has become rather pointless. It's always unclear online to what extent people are engaging in good faith, but if it was then I'm rather sure you've now mentally pigeonholed me as a "doomer" who can't be reasoned with.
Its exactly the opposite. Plants grow larger with higher CO2. And they also reduce in digestive quality significantly as more of the material is lignin.
> At the levels of concentration of CO2 we’re seeing, plants are decreasing in size. Trees grow smaller.
No, they don't. Not due to CO2, anyway (maybe temperature, or changes in precipitation for particular plants).
Even if you want to (inaccurately) argue that specific plants will grow smaller, abundant CO2 will lead to more plants.
> There’s a balance to how much CO2 plants can adapt to and absorb while maintaining their growth and yields.
Again, no. Plants are limited by their genetics, and the availability of inputs, one of the most important of which is carbon. CO2 does not limit a plant's growth. That's just silly.
> Right, my bad... it's not directly the CO2 but the effects of CO2 on climate that is restricting plant growth overall [0]. The net effect is the same.
The net effect is not the same. The net effect is that the earth has been getting greener, in multiple measurable ways, since at least the 1980s.
See my sibling comments containing the IPCC AR6 report citations, where they state that this global greening is happening, and has been happening for decades, with high confidence.
There’s low confidence in the magnitude of this effect in that report.
I don’t think these two things are strongly related.
More leaf surface area and biomass is increasing in tandem with climate models. But there have also been observations that the size and quality of individuals has been affected.
That is a very long chain of dependencies (what is a dependency, what is not can be shown differently than below), meaning there are less and less likely to be many people following the entire chain of dependencies. This is sometimes a key part of how a straw man is constructed.
