More CO2 Closes Stomata On Plants; Closed Stomata Cut Water Vapor Transfer To Atmosphere . . . .

[hatrack]

. . . . and then things get really interesting.

Increasing greenhouse gases in the atmosphere could dry out the Amazon and drench Indonesia, all because rising carbon dioxide levels in the air are changing how plants breathe, according to new research published in Nature Climate Change. James Randerson and Gabriel Kooperman at the University of California, Irvine and colleagues investigated how the physiological response of trees to rising atmospheric greenhouse gas levels affect the output of global climactic models.

The team compared the results of 38 climate simulations based on a fossil-fuel-heavy scenario for the next 100 years, and found a trend of growing asymmetry in rainfall between tropical forests in South America and those in Asia and Africa. This pattern, they say, is driven by regional differences in the role plants play in supplying water to the atmosphere, with South America’s climate more heavily reliant on forests to return water to the air and form clouds, than Indonesia.

According to the scientists, these climactic variations are due to very small changes that occur broadly across all plants as they experience increased atmospheric carbon. As CO2 levels in the atmosphere rise, plants respond by closing their stomata for longer periods. Stomata are the tiny pores on leaf surfaces, stems and bark, that allow plants to absorb carbon dioxide to fuel photosynthesis, while also releasing oxygen and water to the air.

More closed stomata result in plant stems retaining more water and releasing less moisture to the atmosphere through transpiration. The reduction in transpiration in response to increasing CO2 levels isn’t new. Tree ring measurements suggest this process has been underway for the past 150 years as global atmospheric CO2 levels have soared from about 280 parts per million (ppm) to more than 410 ppm today.

EDIT

“Many in the science community were aware that there was a pattern of drying in the Amazon and wetting in Indonesia in the climate model projections,” says Jim Randerson. “What is novel about our study is that we show for the first time that these diverging trends can be traced back to how photosynthesis and tree physiology is represented in the models.”

EDIT

https://news.mongabay.com/2018/06/plant-response-to-rising-co2-levels-may-alter-rainfall-patterns-across-tropics/

[teach1st]

1. I'd like to know more

The physiological reaction of plants to increased CO2 seems to be a thing.

https://sciencing.com/co2-affect-opening-stomata-20980.html
https://www.researchgate.net/post/Stomata_tends_to_close_when_CO2_increases_How_do_we_re-conciliate_that_with_plant_growth_increase_by_CO2_fertilization

But here's the caution about predicting the global effects of the reactions, from the same article in the OP:

Douglas Sheil, a tropical forest ecologist at the Norwegian University of Life Sciences who wasn’t involved in the study, agrees that the study addresses an important issue, but isn’t convinced by the researchers’ analysis, “I am skeptical that [this research] tells us much about the future.” Sheil believes the study reveals more about the inner workings of climate models than changes in the real world. “Models aren’t good enough to make these types of predictions,” he argues.

Although the average of all the models used by the team showed a growing asymmetry between a dryer South America and a wetter Indonesia, not all of the simulations agreed, particularly on what the future holds for Africa.

“The [various] models disagree spectacularly on predicted changes, but the authors still want to argue that the rough suggestion of an agreement that is there is meaningful,” Sheil says.

The authors admit to modeling limitations: “When we look at precipitation changes over individual forests in the tropics, many models show different changes,” Kooperman agrees. But he says that in almost all models “while changes at the individual forest level may differ, the relative pattern of change across the tropics as a whole is consistent.”

We should be doing every thing we can to reduce CO2 emisions. https://www.carbonbrief.org/mission-2020-new-global-strategy-rapidly-reduce-carbon-emissions