Right. There is a pretty simple argument against climate change alarmism that goes as follows. Let F(T) be some function of the global average temperature T - food production is a good one because it's concrete, but you could also talk about some kind of "global human wellbeing" function. Let's assume we are currently at the optimum Tmax. By basic calculus, the first derivative of F(.) at Tmax is zero. So a small increase in the global average temperature, say from Tmax to Tmax+2C, won't have much affect on net food production. This is just a mathematical way of saying that there will be benefits as well as costs associated with global warming, but the costs will probably only exceed the benefits by a small amount.

Someone could counterargue that we are actually above Tmax already, so that the world is suboptimally warm and the derivative of F(T) is already substantially negative. But I think that claim would require some good evidence, and a serious investigation of the issue might actually reveal the opposite - the world is actually suboptimally cool and so we should welcome global warming.