Archive for October, 2017

The greening planet

October 13, 2017


(link to picture)

Reading breathtaking horror stories about rising atmospheric CO2 levels would make mother Earth lol (laugh out loud), if this was possible. Far away from being a catastrophe, increasing CO2 has a demonstrably positive influence on the biosphere. A recent paper by Cheng. et al. in Nature Communications shows this again, using a new method. The title is “Recent increases in terrestrial carbon uptake at little cost to the water cycle” (link), and it has been published in June 2017.

  1. GPP and WUE

The minimum two parameters used to describe the state of the plant biosphere are GPP and WUE.  GPP = Gross Primary Production represents the plant-mass growth; it is measured in gC/(m2*year) = gram carbon per square meter and per year. Now all plant life needs water; normally the availability of water and more important, the efficiency in its use are limiting factors. WUE = Water Usage Efficiency quantifies this; the unit is gC/(mmH2O) = carbon uptake per unit of water loss (for instance gram carbon produced per mm rainfall).

We know since many years that higher CO2 levels reduce the opening of the leaf stomata and as a consequence the water loss by evaporation. So it really does not come as a surprise that WUE has risen during the period 1982-2011 (a period of increasing atmospheric CO2), the basis of the Cheng et al. paper. This figure documents this increase, as found by observations (red line) or calculated from a model used by the authors.

2. Trends in both GPP and WUE

GPP is not a consequence of WUE, but the next figure shows that both parameters (here given as anomalies) increase in step:

The common cause of these increases is atmospheric CO2, and the positive effect is nearly planet-wide, with very few exceptions:

Negative trends correspond to the yellow-red regions, clearly an absolute minority!

3. Conclusion

Rising atmospheric CO2 levels have increased plant production i.e. made the planet greener. On top of this first positive effect, the CO2 gas (which some imbeciles describe as “poisonous”) made the plants more efficient in their water usage: they grow better with less water, the overall ecosystem water use (E) remaining nearly constant!

The authors conclude that “Our results show that GPP has increased significantly and is primarily associated with an increase in WUE“. How is it that these positive aspects of changing CO2 levels are still silenced in the media and the political climate change Zeitgeist?