Globally resolved surface temperatures since the Last Glacial Maximum

Climate changes across the past 24,000 years provide key insights into Earth system responses to external forcing. Climate model simulations(1,2) and proxy data(3-8) have independently allowed for study of this crucial interval; however, they have at times yielded disparate conclusions. Here, we leverage both types of information using paleoclimate data assimilation(9,10) to produce the first proxy-constrained, full-field reanalysis of surface temperature change spanning the Last Glacial Maximum to present at 200-year resolution. We demonstrate that temperature variability across the past 24 thousand years was linked to two primary climatic mechanisms: radiative forcing from ice sheets and greenhouse gases; and a superposition of changes in the ocean overturning circulation and seasonal insolation. In contrast with previous proxy-based reconstructions(6,7) our results show that global mean temperature has slightly but steadily warmed, by 0.5 degrees C, since the early Holocene (around 9 thousand years ago). When compared with recent temperature changes(11), our reanalysis indicates that both the rate and magnitude of modern warming are unusual relative to the changes of the past 24 thousand years. Paleoclimate datasets are integrated with a climate model to reconstruct global surface temperature since the Last Glacial Maximum, showing sustained warming until the mid-Holocene.

Automated summary

Utilizing paleoclimate data assimilation, a reanalysis of global surface temperature over the past 24,000 years has been conducted, showing a slight but steady increase in global mean temperature since the early Holocene by about 0.5 degrees Celsius. The study reveals that the rate and magnitude of modern warming are unusual compared to changes over the past 24,000 years, with key climatic mechanisms including radiative forcing from ice sheets, greenhouse gases, changes in ocean overturning circulation, and seasonal insolation.