30-year satellite-based time series: Is vegetation greening up?

According to the 2007 IPCC report, the average global temperature over the past 100 years increased 0.74ºC. In the past 20-year, environmental observations showed global changes in snow and ice areas, sea level, biological systems (plants, birds etc) and others. Regarding Earth vegetation, satellite data has shown an early greening, especially in the northern latitudes. These results were obtained from the analysis of the nearly two decades of the Normalized Difference Vegetation Index (NDVI) calculated from the Advanced Very High Resolution Radiometer (AVHRR) measurements on board NOAA polar-orbiting satellites. Currently, more then 10 years have been added to the AVHRR-based NDVI time series, the processing improved considerably through the noise reduction, the data were studied comprehensively and what is the most important, were validated against in situ biological observations. Moreover, following biophysical and ecosystem laws the new theory of vegetation health derivation was introduced permitting to develop AVHRR-based products and new applications in agriculture, forestry, human health, climate forcing and others. All of these innovations permitted to develop the new 30-year Global Vegetation Health (GVH) dataset and products. Since, vegetation is a component of carbon sink and source on the Earth, it is important to know if the global warming is triggering vegetation green up, which will distort the balance of the carbon currently and in the future. This paper investigates trend in the 30-year NDVI time series for the entire world, latitudinal circles and regions. The goal is to see if vegetation is greening lately, what regions are affected and how these changes are related to the warming up process..