Why wouldn't they? At least in the U.S. where we aren't feeling the affects of climate change quite as severely as other parts of the world. But, why wait?
https://cgspace.cgiar.org/bitstream/handle/10568/66560/WP119_FINAL.pdf
According to the most recent IPCC report, changes in climates over the last 30 years
have already reduced global agricultural production in the range 1-5 % per decade
globally, with particularly negative effects for tropical cereal crops such as maize and
rice (Porter et al., 2014). In addition, there is now mounting evidence suggesting that
even at low (+2 ºC) levels of warming, agricultural productivity is likely to decline
across the globe, but particularly across tropical areas (Challinor et al., 2014). This
Working Paper provides an overview of projected climate change impacts on crop
production and suitability across Africa, using a combination of literature review,
models and new data analysis
I believe that's from 2013, we already know that crop productions are being threatened and have already been affected by climate change. But, you wouldn't bother to look into it anyway, so what is the point of having this debate with you when one of your boneheaded ideas is to bring the bible into it that you did in another post.