what exactly automatic climate control (for car) ?

Sometimes we are crossing a stretch of road where there is lot of dust and

the automatic climate control suddenly opens the air intake vent,

which should not happen.

I did not realise automatic climate controls also controls the air intake. As far as I know, it only adjusts the air conditioning (or heater) to maintain the temperature set by the car occupant. Is it a new feature? Are you sure its the cause?

I am guessing you are referring to vent mode of the car climate system, not air intake for the engine? If so, I would imagine the dust particulate is interfering with the sensors of the climate control system.

I agree with Mr.Ash,
this system only controls the internal temperature of car, I think..