<p>Ecosystem respiration (ER) is the largest contributor to terrestrial carbon loss. ER responds positively to increasing temperature, so a warming world is hypothesized to lead to additional CO₂ release, potentially further exacerbating climate warming. The long-term influence of thermal changes on this carbon–climate feedback, however, remains unresolved. Here, by compiling data from 221 eddy covariance sites worldwide, we observe decreases in the temperature sensitivity and reference respiration rates of ER with increasing mean annual temperature, suggesting that ER adapts to temperature changes. Our results further reveal that thermal adaptation would eliminate 17.91–31.41% of the anticipated increase in the respiration of unadapted ecosystems under future warming scenarios, equivalent to a net carbon loss of 0.85–11.83 Pg C per year. The increase in respiration rates of terrestrial ecosystems in response to climate warming may thus be lower than predicted, with important consequences for modulating future terrestrial carbon–climate feedback.</p>