Previous sections document the tendency of species to retain their climate envelopes by some combination of range shift and phenological change . However, this tracking of climate change can be incomplete, causing species or populations to experience hotter conditions than those to which they are adapted, and thereby incur 'climate debts'  . The importance of population-level debt is illustrated by a study in which the estimated debt values were correlated with population dynamic trends in a North American migratory songbird, the yellow warbler, Setophaga petechia. Populations that were genetic outliers for their local climate space had larger population declines  than those with genotypes closer to the average values for that particular climate space. Debt values were estimated from genomic analyses independent of the population trends, and were distributed across the species' range in a mosaic, not simply concentrated at range margins, rendering the results robust to being confounded by broad-scale geographical trends . Soroye et al.  found similar results for 66 species of bumble-bees across Europe and North America, with declines in abundances spread throughout species' ranges, but being greatest where populations already near their climate limits were being pushed beyond their climatic tolerances with climate change .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report