CMG: Development of Spatio-Temporal and Multi-Resolution Methods for Detecting the Impact of Volcanic and Solar Forcings in Climate

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This investigation is aimed at developing mathematical methods to identify evidence of volcanic eruptions and variations in the intensity of solar radiation in high resolution proxy climate data of the past thousand years. This is a challenging problem because the records are incomplete and nonstationary, and the climatic response to solar variability and volcanic activity is unknown and probably highly nonlinear. Questions motivating the work are: (1) What has been the influence of explosive volcanism on climate? (2) Has there been a climatic effect of variations in solar irradiance, and if so what modes of climate variability are affected? (3) How much uncertainty in climate proxies, reconstructions, and predictions can be explained by solar and volcanic forcing? The approach is to focus first on the temporal aspects of solar and volcanic signals, then to develop extraction methods for analyzing spatial features on the globe with irregularly spaced data, and finally to combine these in a spatio-temporal model. Techniques to be employed include using 2-D wavelets to characterize spatial features and extending concepts of Kalman filter estimation to non-Gaussian signals. The methods will be tested through statistical simulations using the NCAR Community Climate Model. This research will help to separate the climatic changes caused by human activity from the background of natural variability. It is supported jointly by the Division of Atmospheric Sciences and the Division of Mathematical Sciences through the NSF program, Collaborations in Mathematical Geosciences (CMG).