Climate change is a multivariate process, where changes in the environmental space of a location will likely drive biotic responses of the flora and fauna that inhabit the region. In the face of a rapidly changing climate it is vitally important to understand what the future may hold for our ecosystems. One method commonly applied to understand how dissimilar future climates will be relative to the modern period is no-analog analysis. This has been done for 21st century climates relative to the modern period, but has not been extended through the paleorecord. Using the HadCM3, CCSM3 TraCE-21ka, and PMIP3 climate simulations, we assess global and regional climatic novelty by identifying the closest analogs through the last interglacial (125 ka) for both future (21st century) and modern climates. This baseline offers a full range of glacial and interglacial climate space to explore, and allows us to assess both emergences and disappearances of analog climate conditions throughout the past.
Results/Conclusions
Multiple metrics for quantifying climatic novelty exist (threshold-based approaches, niche-based approaches, and calculations of dissimilarity), each producing variable spatial patterns of novelty. Here we calculate dissimilarity to quantify novelty and no-analog conditions through the last interglacial. This period is meaningful because it captures global climate space with significant overlap of modern and future projected climates. The last interglacial of the Pleistocene, with a climatic optimum ca. 125 ka, was warmer than present and offers a useful analog for some future climate change scenarios. It also captures the onset of glaciation, and the deglaciation of the last 21 ka. Our work shows that nearest climate analogs for the modern period, as well as future climates, existed and disappeared during the onset of Pleistocene glaciation. These results suggest that though climate change may be regionally novel relative to the modern period for some locations, analogs do exist through the paleorecord which in some cases reduce novelty. Nevertheless, novelty remains high in some locations suggesting that some future climates may be unprecedented.