alt Hacker News> 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.
[https://www.mdpi.com/2073-4395/14/6/1236]
In global models of climate change the overall impact on plant growth is significant, but not positive:
| Global above ground biomass is projected to decline by 4 to 16% under a 2 °C increase in climate warming
[https://www.pnas.org/doi/10.1073/pnas.2420379122]
> 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 spent a lot of words arguing with me about things I didn't say.
> you can't easily separate out CO2 concentration from the other impacts of increased CO2
...I never said you could? I explicitly said that there will be changes that require adaptation.
> Global above ground biomass is projected to decline by 4 to 16% under a 2 °C increase in climate warming
That paper is talking about a net reduction in biomass due to projected losses in places with temperature increases exceeding 10 degrees C. It's not just a model, it's science fiction -- it all hinges on the assumptions one makes regarding the proliferation of deserts, which is something we cannot currently predict.
Use the IPCC report instead of cherry-picking studies that support your opinions, and it's obvious that you're wrong. From AR6 Chapter 2, section 2.3.4.3.3 ("Global Greening and Browning") [1]:
> AR5 WGII briefly discussed changes in global vegetation greenness derived from satellite proxies for photosynthetic activity. Observed trends varied in their strength and consistency, and AR5 thus made no confidence statement on observed changes. SRCCL subsequently concluded that greening had increased globally over the past 2–3 decades (high confidence).
> Vegetation index data derived from AVHRR and MODIS depicts increases in aspects of vegetation greenness (i.e., green leaf area and/or mass) over the past four decades (Piao et al., 2020). NDVI increased globally from the early 1980s through the early 2010s (Liu et al., 2015c). Pan et al. (2018a) found NDVI increases over about 70% of the Earth’s vegetated surface through 2013, and Osborne et al. (2018) noted strong upward changes in NDVI in the circumpolar Arctic through 2016. Globally integrated Leaf Area Index (LAI) also rose from the early 1980s through at least the early 2010s (Zhu et al., 2016; Forzieri et al., 2017; Jiang et al., 2017; Xiao et al., 2017) and probably through near-present; for example, Chen et al. (2019) documented an LAI increase over one-third of the global vegetated area from 2000–2017. Although less frequently analysed for temporal trends, Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) likewise increased over many global land areas (particularly China, India, and Eastern Europe) in the past two decades (Figure 2.33) (Forkel et al., 2014; Gobron, 2018; Keenan & Riley, 2018). There are also documented changes in specific vegetation types, such as a 7% rise in global tree cover for 1982–2016 (Song et al., 2018) and an expansion of shrub extent in the Arctic tundra over 1982–2017 (Myers-Smith et al., 2020). 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).
> In summary, there is high confidence that vegetation greenness (i.e., green leaf area and/or mass) has increased globally since the early 1980s. However, there is low confidence in the magnitude of this increase owing to the large range in available estimates.
Plant response to CO2 is not only logical, it's actually happening, and well-documented by a number of different lines of evidence. The only thing you can say in response is that, in the distant future, losses due to desertification might offset this growth. That's fine, it's an argument, but it's basically fortune telling given the scale of the system and the distance into the future. We don't even have the ability to quantify the differences we've observed since the 80s!
[1] https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6... (page 101 in that file)