'Despite the fact the drought was worse than 1988, yields were 50% higher. Part of that are improved hybrids and farming practices but part is the positive effect of CO2, which produces more growth and makes plants more drought resistant. The 1988 drought in 2012 dollars produced between $80B and $120B in losses. Under conditions of atmospheric CO2 enrichment, stomatal apertures typically decrease, thereby reducing stomatal conductance and transpirational water losses from plants.
'Water Stress: When plants are growing under less than optimal conditions of soil water availability, the percent growth enhancement due to atmospheric CO2 enrichment is generally greater than it is when water is readily available to them'