A short piece in Science (AAAS) by Kelly Servick (Mar 6, 2017) ignores carbon dioxide in explaining how increased 
sunlight has caused U.S. corn yields to grow over the past 3 decades. Servick says the increased sunlight was due to decreased atmospheric aerosol content and that projections by global climate models indicate that this will not continue into the future due to rising temperatures and drought. Interestingly, the positive effects of carbon dioxide on plant drought tolerance and fertilizing effect were not mentioned.