Sunday, 26 January 2020

I've spotted another alarmist propaganda fail on Skeptical Science

From Skeptical Science:

They say that the following is a 'Climate Myth':

Earth's current atmospheric CO2 concentration is almost 390 parts per million (ppm). Adding another 300 ppm of CO2 to the air has been shown by literally thousands of experiments to greatly increase the growth or biomass production of nearly all plants. 

OK, why?

1. CO2 enhanced plants will need extra water both to maintain their larger growth as well as to compensate for greater moisture evaporation as the heat increases. Where will it come from? In many places rainwater is not sufficient for current agriculture and the aquifers they rely on are running dry throughout the Earth.

That's their lead argument?

It's not actually true. Plants lose water and absorb CO2 through stomata in their leaves, which open or close to optimise the trade off between losing water and absorbing CO2. All things being equal, with higher CO2 concentrations, stomata don't need to be as big, meaning plant loses less water for a given CO2 intake; or absorb more CO2 for a given amount of water loss.

That's the theory, at least, backed up by what happens in a controlled environment (pumping CO2 into greenhouses). What happens in the real world?

From The Conversation (the rest of the article goes along with the 'consensus'):

Land plants are absorbing 17% more carbon dioxide from the atmosphere now than 30 years ago, our research published today shows. Equally extraordinarily, our study also shows that the vegetation is hardly using any extra water to do it, suggesting that global change is causing the world’s plants to grow in a more water-efficient way.

Skeptical Science's arguments 2 to 6 might be true, untrue or unproven, but 1 is a bad place to start!


Bayard said...

Ah, Skeptical Science, the masters of the meaningless comparison.

They display an alarming lack of knowledge of basic physics: warmer air only causes greater evaporation in the very short term. Very quickly that warmer air reaches its equilibrium relative humidity and evaporation stops. That's why things dry very slowly in hot humid climates. Temperature rises of one or two degrees over a decade aren't going to make the slightest difference.

Mark Wadsworth said...

B, we laughed at that one before. I found something new to laugh at.