I defer to Fred on the conditions that might produce cooling, but I defer to no one on the harmful effects of cooling on the biosphere. Cooling reduces the margins for comfort and safety for endotherms and poikilotherms, but it also has terrible impacts on the fauna and crops.
The claims that warming will cause drought are weak at best, since any idiot knows that a warmer climate will produce more evaporative contribution to atmospheric water vapor, so the effect of warmer would be nil or even a net increase in precipitation.
increased carbon dioxide also has a direct impact on plant resistance to drought.
So here comes Fred, the iconic climate researcher, and prolific writer, and his concerns about this potential for cooling–maybe the Club of Rome and the scaremongers can pick up this issue and make some noise–but it would ruin their crusade to devolve the industrial revolution and modernity.