Deciphering Temperature Seasonality in Earth's Ancient Oceans

Ongoing global warming due to anthropogenic climate change has long been recognized, yet uncertainties regarding how seasonal extremes will change in the future persist. Paleoseasonal proxy data from intervals when global climate differed from today can help constrain how and why the annual temperature cycle has varied through space and time. Records of past seasonal variation in marine temperatures are available in the oxygen isotope values of serially sampled accretionary organisms. The most useful data sets come from carefully designed and computationally robust studies that enable characterization of paleoseasonal parameters and seamless integration with mean annual temperature data sets and climate models. Seasonal data sharpen interpretations of-and quantify overlooked or unconstrained seasonal biases in-the more voluminous mean temperature data and aid in the evaluation of climate model performance. Methodologies to rigorously analyze seasonal data are now available, and the promise of paleoseasonal proxy data for the next generation of paleoclimate research is significant. The seasonal cycle defines climate and its constraints on biology, both today and in the deep past. Paleoseasonal data improve proxy-based estimates of mean annual temperature and validate Earth System Model simulations. Large, internally consistent data sets can reveal robust spatiotemporal climate patterns on the ancient Earth and how they change with pCO(2). Computational tools enable rigorous numerical analysis of paleoseasonal data for comparison with other paleoclimate data and model output.