View Single Post
Old 06-06-2018, 08:36 PM   #16 (permalink)
RedDevil
Master EcoWalker
 
RedDevil's Avatar
 
Join Date: Dec 2012
Location: Nieuwegein, the Netherlands
Posts: 3,998

Red Devil - '11 Honda Insight Elegance
Team Honda
90 day: 47.72 mpg (US)
Thanks: 1,711
Thanked 2,245 Times in 1,454 Posts
Quote:
Originally Posted by jamesqf View Post
What this is overlooking is the temperature dependence of photosynthesis. C3 efficiency starts dropping around 25C, and shuts down entirely around 45C. C4 photosynthesis works at a bit higher temperature, peaking around 35C, but even it shuts down around 55C: https://kuensting.org/school/bb/cell...osynthesis.htm

So you put enough CO2 into the air to raise temperatures into this range (even if only in the tropics), and then goes a chunk of the biosphere. And of course it's a positive feedback: fewer plants recycling CO2 means more goes into the atmosphere, which means more temperature increase, which means even less photosynthesis...
There also is a dependency to CO₂ levels; higher CO₂ allows photosynthesis at higher temperatures in C3 plants and reduces their water usage.

So on the one hand CO₂ raises the global temperature which will increase the size of regions where temperature is the limiting factor on photosynthesis, on the other hand it allows some plants to make use of conditions that would otherwise impede them. Provided nutrients suffice.
__________________
2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.2 Gmeter or 0.13 Mmile.


For confirmation go to people just like you.
For education go to people unlike yourself.
  Reply With Quote