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.
Highlights
Stomatal conductance links plant water use and carbon uptake, and is a critical process for the land surface component of climate models
The increase in future (2020–2099) simulated TXx resulting from changing the representation of gs is approximately 4–5 °C over Western Europe
This sensitivity to gs can be put into context by recognising that this change is equivalent to more than half the increase projected under RCP8.541 (> 1370 ppm CO2 equivalent in 2100) by an ensemble of climate models for 2081–210045
Summary
Stomatal conductance links plant water use and carbon uptake, and is a critical process for the land surface component of climate models. Heatwaves are associated with large-scale synoptic states[15,16], which are influenced by modes of climate variability[17] It is well established from observational[18] and modelling studies[19,20] that heatwaves are strongly modulated by the land surface if the synoptic scale weather generates persistent anticyclonic patterns and the planetary boundary-layer strongly couples the land to the atmosphere over consecutive days[21]. Under these circumstances, heatwaves intensify as desiccated soils and a surface radiation balance dominated by the exchange of sensible heat is coupled with the boundary-layer to lead to events such as the “mega-heatwaves” experienced in Europe during 2003 and 201019,21. Given that heatwaves are associated with synoptic state and persistent anticyclonic conditions or so-called “blocking/persistent highs”[31,32], these feedbacks are more likely to affect heatwave intensity than duration or frequency
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