It is critical that we understand the effects of climate change on natural systems if we ever hope to predict or mitigate consequent changes in diversity and ecosystem function. In order to identify coherent ‘fingerprints’ of climate change across Earth’s terrestrial and marine ecosystems, various reviews have been conducted to synthesize studies of climate change impacts on individual species, assemblages and systems. These reviews help to make information about climate change impacts accessible for researchers as well as for the general public and policymakers. As such, these reviews can be highly influential in setting the direction of policy and research. Unfortunately, due to limited data availability, the majority of reviews of climate change impacts suffer from severe taxonomic and geographic biases. In particular, tropical and marine systems are grossly underrepresented, as are plants and endothermic animals. These biases may preclude a comprehensive understanding of how climate change is affecting Earth’s natural systems at a global scale. In order to advance our understanding of climate change impacts on species and ecosystems, we need to first assess the types of data that are and are not available and then correct these biases through directed studies and initiatives.