27 March, 2016

Will plants' response to increased CO2 make heatwaves more intense than thought?

The report by Peter Hannam below seemed like a possible real concern if ever we do get global warming. But I somehow knew that they would have ignored something important so I looked up the underlying journal article -- abstract thereof also reproduced below. It is all just modelling rubbish. When Warmist models show predictive skill will be the time to take notice of them. It hasn't happened yet.

But there is something amusing in the article nonetheless. They seem to base their claims on how an individual leaf stoma reacts to higher CO2 but forget to look at the whole plant. That higher CO2 levels will produce bigger plants and hence more stomata seems to be overlooked. With more stomata the overall water release may remain unchanged.

Warmists are such a laugh! Junk science all the way. It's such junk that even a humble social scientist like me can see through it. And shifty old Peter Hannam swallows it all hook, line and sinker. He must never ask any questions


Peter Hannam

Heatwaves in the northern hemisphere may become as much as 5 degrees warmer than previously estimated by mid-century because plants' response to higher carbon dioxide levels has been miscalculated, according to new research by Australian scientists.

As atmospheric levels of the greenhouse gas increase, plant stomata – the tiny pores on leaves that open to take in CO2 and let out water vapour – won't need to open as much.

"There's less water vapour being lost so you have a net warming effect," said Jatin Kala, a lecturer from Murdoch University and lead author of the paper that was published Monday in Nature Scientific Reports.

The researchers used data from 314 plant species across 56 field sites to examine how plants responded. Existing climate models had assumed all plants would trade water for carbon in exactly the same way.

Needle-leaf forests, tundra and agricultural land used for crops would likely suffer the biggest temperature increases. Heatwaves from Europe to China were likely to become 3-5 degrees hotter than the already higher base expected from global warming, Dr Kala said.

"These more detailed results are confronting but they help explain why many climate models have consistently underestimated the increase in the intensity of heatwaves and the rise in maximum temperatures when compared to observations."

The results do not necessarily apply to southern hemisphere regions to the same extent. "We don't have an observation of how Australian vegetation will respond to rising CO2," he said.

CSIRO, the Bureau of Meteorology and the ARC Centre of Excellence for Climate System Science developed the Australian Community Climate and Earth System Simulator (ACCESS) model used in this study.

SOURCE

Impact of the representation of stomatal conductance on model projections of heatwave intensity

Jatin Kala et al.

Abstract

Stomatal conductance links plant water use and carbon uptake, and is a critical process for the land surface component of climate models. However, stomatal conductance schemes commonly assume that all vegetation with the same photosynthetic pathway use identical plant water use strategies whereas observations indicate otherwise. Here, we implement a new stomatal scheme derived from optimal stomatal theory and constrained by a recent global synthesis of stomatal conductance measurements from 314 species, across 56 field sites. Using this new stomatal scheme, within a global climate model, subtantially increases the intensity of future heatwaves across Northern Eurasia. This indicates that our climate model has previously been under-predicting heatwave intensity. Our results have widespread implications for other climate models, many of which do not account for differences in stomatal water-use across different plant functional types, and hence, are also likely under projecting heatwave intensity in the future.

SOURCE






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