Thread by @ncdave4life

@IBergwiesel @Dardedar @rahmstorf @IngersolRobert 1/6 Most plants don't get water from the air, they get it from the soil. Lower humidity is associated with lower plant growth rates, but that's because it is correlated with soil moisture levels, and lower plant growth rates reduce transpiration, thereby reducing humidity.

@IBergwiesel @Dardedar @rahmstorf @IngersolRobert 2/6 As atmospheric CO2 levels increase, plants' water requirements decrease, due to the reduced stomatal conductance & transpiration needed to absorb CO2 from the air. So if CO2 levels rise you can get reduced transpiration and thus reduced humidity WITHOUT slowing plant growth.

@IBergwiesel @Dardedar @rahmstorf @IngersolRobert 3/6
doi.org/10.1038/s41467…

Cheng 2017 reports that the global increase in transpiration due to increased foliage has been offset by a decrease in transpiration due to improved water use efficiency, resulting in almost no change in net transpiration.

@IBergwiesel @Dardedar @rahmstorf @IngersolRobert 4/6
"Land plants are absorbing 17% more [CO2] from the atmosphere now than 30 years ago [yet] 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."
theconversation.com/rising-carbon-…

@IBergwiesel @Dardedar @rahmstorf @IngersolRobert 5/6 There is no scientific evidence to support the idea that CO2-driven climate change will be harmful to crops. It's complete nonsense.

This has been extensively studied, by agronomists (a/k/a real scientists, who actually measure things). E.g.
ncbi.nlm.nih.gov/pubmed/26929390

@IBergwiesel @Dardedar @rahmstorf @IngersolRobert 6/6 The bottom line is that the benefits of higher CO2 levels are large and well-measured; the significant harms are all hypothetical, and mostly implausible.