Climate Change Experienced by Life on Earth-Drivers and Mechanisms of Future Trends in Microclimates.

Microclimate, the climate directly experienced by organisms, is crucial for understanding ecological responses to climate change, yet its long-term dynamics and the drivers of decadal microclimate changes remain underexplored in ecology and global change biology. Microclimate changes do not necessarily track macroclimate trends. Changes in meteorological conditions (e.g., cloud cover, wind patterns) and vegetation dynamics (e.g., canopy opening, desertification in drylands, shrub encroachment in the tundra) associated with climate change can lead to locally divergent microclimate trends, thereby altering spatial variability. Understanding and quantifying how macroclimate change translates to fine-scale microclimate change experienced by organisms, populations and communities is therefore essential for predicting ecological responses to global environmental change. This review examines how macroclimate change drives microclimate changes as experienced by life on Earth-and how these micro-scale changes may, in turn, feed back into the regional and global climate system. Our primary focus is on near-surface air and soil temperature-due to their relevance to most terrestrial organisms and ecosystem processes. The review is structured around three pathways of microclimate changes: (I) direct effects of changes in meteorological conditions, (II) indirect effects via vegetation changes, and (III) feedbacks between microclimate and climate change. Using three mechanistic model simulations in real-world landscapes, we illustrate and quantify the key mechanisms that lead to divergent warming trends. We show that microclimate change emerges from interacting atmospheric, land-surface, and biophysical processes, which can differ substantially across space and time. Predicting future microclimates therefore requires accounting for these processes and their temporal dynamics. By providing an accessible synthesis of these processes, this review aims to strengthen links between ecology and atmospheric science and improve our understanding of how climate change translates into microclimatic conditions relevant to life on Earth.