Finally , the positive effects of elevated CO2 on agricultural production will also saturate and in addition, create a change in the nutritional quality of grains

These effects increase agricultural productivity to a certain extent but, rising GHG emissions contribute to increased frequency and intensity of extreme weather events, negatively impacting plant and crop growth, and yield, such as risk of extreme heat stress occuring at crop anthesis.

Elevated atmospheric concentration enhances rate of photosynthesis and reduces water transpiration from plant stomata. These combined effects stimulate plant growth, especially for plants following a C3 photosynthetic pathway (eg wheat)

As atmospheric CO2 increases, other risks come into play and become more dangerous as certain tipping points in the earth system are crossed (e.g., melt of arctic ice sheet, influencing general atmospheric and ocean circulation patterns)

First of all, one has to consider all direct and indirects aspects of rising CO2 and its effect on climate change