Isolated and combined effects of elevated temperature and partial pressure of CO₂ (PCO₂) on resting oxygen uptake (MO2rest) and absolute aerobic scope (AAS). Data are log response ratios (lnRR) of $MO2rest$ (A and B) and AAS (C and D) in marine invertebrates (A and C) and fish (B and D) to elevated temperature alone (red symbols), elevated PCO₂ alone (blue symbols) and the combined treatment (purple symbols). Different shapes indicate different taxonomic groups (upright triangle, gastropod; circled cross, cephalopod; hexagon, bivalve; inverted triangle, crustacean; diamond, echinoderm; cross, cnidarian; square, elasmobranch; and circle, teleost). Note that the invertebrate species are all calcifying because there were no comparable data available for non-calcifying species. Continous lines indicate mean ± 95% confidence intervals. In (D), lnRR from studies investigating CO₂ only (indicated by plus signs) have been added to illustrate the variation in responses, because this is not reflected in the studies having investigated both temperature and CO₂. The complete data set and reference details are available in Supplementary Table ST3_MO2rest and ST3_AAS.