Monday, 23 January 2017
Earth-Observing satellites provide global observations of many geophysical variables. As these variables are derived from measured radiances, the underlying radiance data are the most reliable sources of information for change detection. Here we identify statistically significant trends in the color and spatial texture of Earth as viewed from multiple directions from the Multi-angle Imaging SpectroRadiometer (MISR), which has been sampling the angular distribution of scattered sunlight since 2000. Globally, our results show that the Earth has been appearing relatively bluer (up to 1.6% per decade from both nadir and oblique views) and smoother (up to 1.5% per decade only from oblique views) over the past 15 years, while regional shifts in color and texture, which are significantly larger than global means, are observed, particularly over polar-regions, along the boundaries of the subtropical highs, the tropical western Pacific, Southwestern Asia, and Australia. We demonstrate that the large regional trends cannot be explained either by uncertainties in radiometric calibration or variability in total or spectral solar irradiance; hence they reflect changes internal to Earth’s climate system. The 15-year-mean true color composites and texture images of the earth at both nadir and oblique views are also presented for the first time.
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