Abstract
A rapidly warming climate is driving changes in biodiversity worldwide, and its impact on insect communities is critical given their outsized role in ecosystem function and services. We use a long‐term dataset of North American bumble bee species occurrences to determine whether the community temperature index (CTI), a measure of the balance of warm‐ and cool‐adapted species in a community, has increased given warming temperatures. CTI has increased by an average of 0.99°C in strong association with warming maximum summer temperatures over the last 30 years with the areas exhibiting the largest increases including mid‐ to high latitudes as well as low and high elevations—areas relatively shielded from other intensive global changes. CTI shifts have been driven by the decline of cold‐adapted species and increases in warm‐adapted species within bumble bee communities. Our results show the pervasive impacts and ecological implications warming temperatures pose to insects.