I don't think it is possible with exactly 33 questions. It will probably require more than that. Binary numbers have the property of adding twice as many numbers +1 for every new bit. For example if you already have 7 bits and you add an 8th one, then you'll be able to represent 127 numbers with that bit off and 128 numbers with that bit on.

To properly mimic this property with yes/no questions, you will have to come up with questions that divide the whole Earth's population equally AT EVERY NEW QUESTION. Even the most obvious one, "are you (fe)male?" is slightly biased toward men (according to wikipedia). At every question that skew your 50/50, you'll have to add another question beyond 33 to catch up with this.