@JohnGritt
It is simple:

1St, most scientist know, this is a problem with 1 000 000 variables. in short, they don't know.

2nd, an idea becomes popularized. it becomes political

3rd, there is a wide social pressure on scientists to ignore 99% of factors as long as they can agree with the public

now, only the bravest of scientist have tbe balls to say the basic premisse of any scientific discovery. "We don't know"