Editing IPCC:AR6/WGII/Chapter-3 (section)

=== 3.3.1 Introduction ===

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This section assesses new evidence since AR5 ( [[#Pörtner--2014|Pörtner et al., 2014]] ) and SROCC ( [[#Bindoff--2019a|Bindoff et al., 2019a]] ) regarding biotic responses to multiple environmental drivers. It assesses differential sensitivities among life stages within individual organisms, changing responses across scales of biological organisation and the potential for evolutionary adaptation to climate change (e.g., [[#Przeslawski--2015|Przeslawski et al., 2015]] ; [[#Boyd--2018|Boyd et al., 2018]] ; [[#Reddin--2020|Reddin et al., 2020]] ), providing examples and identifying key gaps and uncertainties that limit our ability to project the ecological impact of multiple climate-induced drivers (Figure 3.8a). The assessment includes physiological responses to single environmental drivers and their underlying mechanisms ( [[#3.3.2|Section 3.3.2]] ), the characteristics of multiple drivers and organisms’ responses to them ( [[#3.3.3|Section 3.3.3]] ), short-term acclimation and longer-term evolutionary adaptation of populations ( [[#3.3.4|Section 3.3.4]] ), and it concludes with an assessment of progress in upscaling laboratory findings to ecosystems within ''in situ'' settings (Figure 3.8b; [[#3.3.5|Section 3.3.5]] ).

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'''Figure 3.8 |''' '''The state of knowledge regarding ecological responses to environmental drivers in experimental settings.'''

'''(a)''' Schematic indicates where themes are discussed within [[#3.3|Section 3.3]] , and how they jointly inform policy. (Adapted from [[#Riebesell--2014|Riebesell and Gattuso, 2014]] ).

'''(b)''' The hierarchy of accumulating physiological knowledge (grey layers), from single (e.g., [[#Pörtner--2012|Pörtner et al., 2012]] ) to multiple drivers, and from simple outcomes (e.g., [[#Sciandra--2003|Sciandra et al., 2003]] ), interactions among drivers (e.g., [[#Crain--2008|Crain et al., 2008]] ) and identification of physiological roles of drivers (e.g., [[#Bach--2015|Bach et al., 2015]] ) to mechanistic understanding of drivers (e.g., [[#Thomas--2017|Thomas et al., 2017]] ). At present, the upper grey layer has been achieved, in full, for two drivers (e.g., temperature and nutrient concentrations), with validation of dual controls on phytoplankton growth rate ( [[#Thomas--2017|Thomas et al., 2017]] ). Hatched layers denote major advances since WGII AR5 [[IPCC:Wg2:Chapter:Chapter-6|Chapter 6]] ( [[#Pörtner--2014|Pörtner et al., 2014]] ). The green layer indicates the level of understanding potentially needed to project the response of marine life subjected to multiple drivers. Red horizontal arrows indicate the influence of confounding factors on our current understanding, including population genetics, fluctuating oceanic conditions or extreme events.

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