Dynamic changes in terrestrial net primary production and their effects on evapotranspiration

The dramatic increase of global temperature since the year 2000 has a considerable impact on the global water cycle and vegetation dynamics. Little has been done about recent feedback of vegetation to climate in different parts of the world, and land evapotranspiration (ET) is the means of this feedback. Here we used the global 1km MODIS net primary production (NPP) and ET data sets (2000-2014) to investigate their temporospatial changes under the context of global warming. The results showed that global NPP slightly increased in 2000-2014 at a rate of 0.06PgCyr(-2). More than 64% of vegetated land in the Northern Hemisphere (NH) showed increased NPP (at a rate of 0.13PgCyr(-2)), while 60.3% of vegetated land in the Southern Hemisphere (SH) showed a decreasing trend (at a rate of -0.18PgCyr(-2)). Vegetation greening and climate change promote rises of global ET. Specially, the increased rate of land ET in the NH (0.61mmyr(-2)) is faster than that in the SH (0.41mmyr(-2)). Over the same period, global warming and vegetation greening accelerate evaporation in soil moisture, thus reducing the amount of soil water storage. Continuation of these trends will likely exacerbate regional drought-induced disturbances and point to an increased risk of ecological drought, especially during regional dry climate phases.