Editing IPCC:AR6/WGII/Chapter-2 (section)

=== 2.1.3 Guide to Attribution and Traceability of Uncertainty Assessments ===

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For biological systems, we use the framework for detection and attribution outlined in AR5, in which biological changes observed are not attributed to global but rather to local or regional climate changes ( [[#Parmesan--2013|Parmesan et al., 2013]] ; [[#Cramer--2014|Cramer et al., 2014]] ). However, global distribution of regional responses is desirable to achieve generality, and data in prior reports were concentrated from the Northern Hemisphere. The critique of ‘global’ studies by ( [[#Feeley--2017|Feeley et al., 2017]] ) argues that their naming is misleading, that most of them are far from global, and that a considerable geographic and taxonomic bias remains. This bias is diminishing, as regional data from the Southern Hemisphere is added and there is now representation from every continent.

Overall confidence in attributing biological changes to climate change can be increased in multiple ways ( [[#Parmesan--2013|Parmesan et al., 2013]] ), four of which we list here. First, confidence rises when the time span of biological records is long, such that decadal trends in climate can be compared with decadal trends in biological response, and long-term trends can be statistically distinguished from natural variability. Second, confidence can be increased by examining a large geographic area, which tends to diminish the effects of local confounding factors ( [[#Parmesan--2013|Parmesan et al., 2013]] ; [[#Daskalova--2021|Daskalova et al., 2021]] ). Third, confidence is increased when there is experimental or empirical evidence of a mechanistic link between particular climate metrics and a biological response. Fourth, confidence is increased when particular fingerprints of climate change are documented that uniquely implicate climate change as the causal driver of the biological change ( [[#Parmesan--2003|Parmesan and Yohe, 2003]] ). These conditions constitute multiple lines of evidence, which, when they converge, can provide ''very high confidence'' that climate change is the causal driver of an observed change in a particular biological species or system ( [[#Parmesan--2013|Parmesan et al., 2013]] ).

Important factors that may confound or obscure effects of climate change are the presence of invasive species, changes in land use (LULCC) and, in freshwater systems, eutrophication ( [[#IPCC--2019a|IPCC, 2019a]] ). The temporal and spatial scale of studies also affects estimates of impacts. The most extreme published estimates of biological change tend to be derived from smaller areas and/or shorter time frames ( [[#Daskalova--2021|Daskalova et al., 2021]] ); a recent large global analysis of data for 12,415 species found that differences in study methodology accounted for most of the explained variance in reported range shifts ( [[#Lenoir--2020|Lenoir et al., 2020]] ). The importance of LULCC is frequently stressed, but there is a paucity of studies actually quantifying the relative effects of climate change and LULCC on species and communities. ( [[#Sirami--2017|Sirami et al., 2017]] ) found only 13 such studies: four concluded that effects of LULCC overrode those of climate change, four found that the two drivers independently affected different species and five found that they acted in synergy.

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