And you can't accomplish that by pointing your gun at the threat and by yelling "stop, stop, stop"? If there is a lethal force situation, then pointing your gun at the threat and giving a
verbal warning is the appropriate approach if you decide to give a warning at all.
Face it, firing a warning shot is plain stupid. Anyone ever having fired a gun without hearing protection knows why. Also, what's your backstop? The ground right next to your feet? The ground right next to your attacker's feet? If it is any kind of pavement, then that round can go pretty much anywhere. In any case, a warning shot is legally the same as a miss.
Also, knowing that you carry a 1911 in .45 ACP, reducing your already low capacity by one round for a warning shot is double stupid.