This is just a “thinking out loud” thread. No need to reply.

Question. Can the global vegetation results from NASA’s Terra satellite be fed into Global Climate Model software? Has this already been done? What is the result if it is done?

Starting point https://sci-hub.tw/https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2486.2001.00383.x
“Global response of terrestrial ecosystem structure and function to CO2 and climate change: results from six dynamic global vegetation models”, Cramer et al., 2001.

I know, it’s a long time ago, but it does at least consider a range of different vegetation responses to atmospheric CO2, so may include one or more that matches the Terra satellite data.

“Canopy phenology includes the seasonal timing of budburst, senescence and leaf abscission in response to temperature and/or drought. Vegetation dynamics are based on annual net primary production and biomass growth; they include competition among plant functional types, probabilities of natural disturbance (fire, general mortality) and succession (replacement of plant functional types over time) following disturbance.”

Damn acronyms,
NPP is Net Primary Productivity, I know that.
NEP is net ecosystem production. Is that the growth rate of biomass?
ptf = ?

The six supposedly different vegetation models aren’t all that different. Photosynthesis is based on Farquhar (1980) and Collatz (1992) (5 of 6 models) or “empirical” (1 of 6 models).

So essentially there are only 2 photosynthesis models, one of which, being empirical, is probably unobtainable. The other is old. Results are these.

You only need to take account of the dark blue line here, the other two lines are nobbled models with various components removed. NPP is Net Primary Productivity, the rate of growth of natural forests.

Clearly, increased atmospheric CO2 is predicted to be good for forests. We’re talking about anthropogenic CO2 giving a 50% increase in natural forest biomass in the long term.

But is that prediction good enough? From the Terra satellite we know that NPP has increased faster than these predictions.

The references are:

Farquhar (1980) A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species.Planta,149,78-90.

Collatz (1992) A coupled photosynthesis – stomatal conductance model for leaves of C4 plants. Australian Journal of Plant Physiology, 19, 519-538.

Since C3 plants make up 95% of Earth’s plant biomass (according to wikipedia), and include all trees, most shrubs and some grasses, it looks as though the core calculations of environmental impacts from (almost) all Climate Modelling software reside in a single thirty-eight year old paper. Clearly, that paper is worth looking up.

https://www.researchgate.net/profile/Graham_Farquhar/publication/259201703_A_biochemical_model_of_photosynthetic_CO/links/02e7e516c5ca5adcb7000000.pdf

(Side note. It may be important to find out if bamboo is a C3 plant. Bamboo is the dominant species in some forests, and being a fast-growing grass may or may not be a C3).

Clearly, increased atmospheric CO2 is predicted to be good for forests. We’re talking about anthropogenic CO2 giving a 50% increase in natural forest biomass in the long term.

That would be good I suppose if we didn’t cut them down at an alarming rate, the Earth can’t keep up

Cymek said:

Clearly, increased atmospheric CO2 is predicted to be good for forests. We’re talking about anthropogenic CO2 giving a 50% increase in natural forest biomass in the long term.

That would be good I suppose if we didn’t cut them down at an alarming rate, the Earth can’t keep up

Agree. Particularly hardwoods in tropical forests, but also softwoods in scandinavia.

PMSL at Farquhar (1980) “A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species”. Planta,149, 78-90.

This was never intended to be a definitive paper on photosynthesis. Nothing obviously directly wrong with it, but the descriptive text …

“integrate current knowledge” – current knowledge in 1980, I should hope that we have learnt more since then.

“conflicting evidence … we assume … but recognise that this is an oversimplification” – this is supposed to be definitive !?

“simplified photosynthetic cycles” – not definitive.

Free parameter φ. Free parameter ‘f’.

“several factors may limit”, “is usually limited by”, “controversy exists over”, “if the enzyme reaction is”, “we see that several factors may limit the rate”, “the fraction f may increase with leaf thickness”

Table 1 gives alternative possibilities for four different parameters.

In short, Farquhar’s 1980 paper is a product of its time, with numerous uncertainties, simplifications, oversimplifications and in one or two cases downright guesses. It could not possibly by any stretch of the imagination be called definitive thirty-eight years later. And yet it is the core of the environmental prediction component of current global climate models.

Looks like I need to look into this some more – in particular to look at the photosynthesis subroutine of at least one global climate model.

> Looks like I need to look into this some more – in particular to look at the photosynthesis subroutine of at least one global climate model.

There used to be a CSIRO / BOM global climate model called ACCESS. Lousy choice of name. But CSIRO shut down its involvement in that two years ago so now it’s only BOM.