Cancer pagurus from the North Sea were exposued to acute, step-wise warming under two levels of CO2. The exposure to either normocapnic (450 µatm CO2) or hypercapnic (1350 µatm CO2) conditions was randomized on a temperature ramp between 12 and 20°C. Steps of constant temperatures were 10 h every two °C (12, 14, 16, 18, 20°C). Seawater chemistry (temperature, salinity, ph, PCO2) was analysed at 12 and 20°C. pH is given on the free scale and used for subsequent calculation of totalk alkalinity (TA), bicarbonate concentration and dissolved inorganic carbon (DIC).Physiological parameters were recorded over the course of a temperature ramp: Whole-animal metabolic rate (MO2) via flow-through respirometry. Heart rates (HR) via infrared photoplethysmography (IR-PPG). The integral of the raw signal of the plethysmogrpah served as a proxy for cardiac stroke volume (SV). Is was normalized to a control SV of 0.2 mL, based on literature references. The product of HR and SV equals cardiac output (CO).The difference between logtime_MO2 and logtime is that MO2 (whole-animal metabolic rate) were sometimes recorded with an inconsistent temporal delay compared to the other parameters. For accurate correlation of the data, readers are kindly asked to use the correct logtimes for each parameter (i.e. "logtime_MO2" for "MO2" and "logtime" for the others).In a parallel experiment, ventilatory water flow in the excurrent channel of the gill chambers, as well as haemolymph flow in the arteria sternalis and branchial veins was determined via phase-contrast magnetic resonance imaging (MRI). The lateral contractility of the heart was determined from self-gated cardiac MRI movies at 12 and 20°C during diastole and systole.