Ray, doubling of CO2 levels causes not only 30% increase of rice yields, but potentially also a 300% increase of air turbulence for airplanes. Warming temperatures create larger storms and as the jet stream shifts northward, we get more frequent and stronger instances of air turbulence which affect air traffic.
And not only that. In order for more biomass to grow due to the increased CO2 levels, the soil must provide nutrients and there must be the right amount of water. Both are not guaranteed as a result of climate change (droughts vs increased precipitation). In addition, harmful (sometimes exotic) insects usually thrive at higher temperatures and weeds can also compete with the more desirable plant growth. This may also increase the need to use herbicides, insecticides and additional fertilizer, and if a runoff is caused by heavy rainfall, the aquatic life may also suffer from algae blooms in a competition for oxygen.
Climate change deniers usually cherry-pick one specific benefit, but deliberately ignore the (more) negative effects that are almost inevitable in a closed-loop ecosystem. We do not live in a controlled laboratory, sheltered from the outside world, but we live as part of a large system that struggles to adapt to the unprecedented pace of change.
BTW, talking about extreme weather, we are experiencing our third heatwave in 3 months time this year, temperatures have never been this high in the respective months since they were first formally recorded more than 100 years ago. The numbers of excess deaths for this run are not known yet (we have another day and a half to go before normal temperatures set in), but the National Heatplan is in effect again.
Cheers,
Bart