The Statistical Relationship Between Remotely Sensed Vegetation and Climate for the Last 15 years is not Reflective of the last 30 years

Abstract:

Inter-annual variations in temperature as well as the longer-term trend of global warming are changing the mean state of the biosphere as well as how the biosphere and climate are coupled. Identifying changes in how the biosphere responds to climate is critical for predicting and understanding alterations to the dynamics of the carbon and hydrological cycles.

Global satellite observations of vegetation are available from 1981 – 2011 with the Normalized Difference Vegetation Index third generation (NDVI 3g) calculated from the Advanced Very High Resolution Radiometer. The launch of additional instruments, such as the Moderate Resolution Imaging Spectroradiometer (MODIS), in the past 15 years greatly improves the detail and resolution of remotely sensed data available to observe vegetation and physical climate. Using a monte carlo technique we map outlier years across the globe and find the areas of greatest change in the statistical relationship across the Midwest, Europe, central South America and the Sahel.

With 30 years of research quality data on the surface greenness we show that the regressions over the last 15 years between NDVI and temperature are significantly different than the 30-year regression. By looking at the statistical relationships between the biosphere and longer-term temperature measurements we can better understand how representative shorter datasets will be of long-term processes and how much the coupling in the combined climate-biosphere system is changing.