Title: Patterns of forced changes in spatiotemporal climate reconstructions of the Common Era
Abstract: Spatiotemporal climate reconstructions offer opportunities to examine patterns of climate anomalies in both time and space and use these to diagnose causal mechanisms linked to radiative forcing or internal modes of ocean-atmosphere variability. Here, we use two recent Common Era temperature reconstructions to investigate the response of the climate system to volcanic eruptions as well as to radiative changes due to solar variability and greenhouse gas emissions. Our new NTREND field reconstruction of Northern Hemisphere summer temperatures shows coherent, broad-scale cooling associated with large tropical volcanic eruptions. Cooling persists in some cases for 2 or more years following eruptions and different eruptions reveal different magnitudes and spatial patterns that are not clearly associated with the estimated radiative forcing. We also detect temperature anomalies linked to centennial-scale changes in insolation and we quantify in time and space the temperature patterns linked to the Medieval Climate Anomaly, Little Ice Age, and modern warming. The PAGES2k Oceans2k High Resolution (HR) reconstruction of tropical sea surface temperatures shows cooling of the western Pacific and Indian Ocean in response to well-dated tropical eruptions but no statistically significant response in the eastern tropical Pacific, suggesting a reduction in the tropical Pacific temperature gradient but not a canonical El Nino pattern. Climate models simulate an overall larger cooling in the western Pacific and Indian Ocean than the reconstructions and produce a variety of anomalies in the eastern Pacific. New spatiotemporal climate reconstructions can provide useful benchmarks for comparing proxy reconstructions with model simulations and may help identify possible sources of disagreement.