That's a good point. If someone is opposed to both climate change and GMO food on the basis of "this is too complex to understand, so let's not touch it", that

That's a good point. If someone is opposed to both climate change and GMO food on the basis of "this is too complex to understand, so let's not touch it", that would be an intellectually consistent position. But more often than not, that's not the argument I hear from climate-change-alarmists. Most of the time, the argument they are making falls more into the camp of "we understand the science well enough to know that climate change is definitely happening and will have negative repercussions on humanity. The scientific consensus on this is solid, and we should trust in that scientific consensus." The second argument sounds a lot stronger than the first, which is why most environmentalists go with that argument. But it's intellectually inconsistent with their opposition to GMO.