Science can input hundreds of thousands of common words, phrases, syllables and sounds into a computer to come up with the most practical language for international communication in the spoken and written word. We have the computer technology to do so right now. I would bet English wins because many foreigners already speak the language as a second choice for non-native speakers.
An international language should make use of every possible variation in phonemes including clicks, every vowel, every consonant, every tone. Every combination. In doing so people can not only learn an international language to communicate with each other in but also exercise the full capacity of human capability in sound production. This sort of exercise will be good for people's brains and so have the incidental effect of promoting innovation.
It is probably going to be impossible to have every major nation in the world adopt a common language for global communication because we are all attached to our cultures. However, if it is to happen, it needs to be chosen on more than a purely scientific basis but needs to take into account feelings and attachments.
No, I don't think that science is required to choose the best language for international communication. It's something that I think we are going to have to leave up to the market, or just people in general, to decide. Right now, that language appears to be English. About a hundred years ago, it was French. A hundred years from now, it might be Spanish.
No, science cannot help choose the best language for international communication, because there still needs to be a judgment call involved. What defines the best language? Does it depend on how many people speak that language? The economies of the nations speaking the language. At some point, some real live person, rather than a blank, empty set of facts, needs to make a decision about what is better than another.
Science has the same capacity as Capitalism to absorb criticism and reinvent itself by using what it is criticized for to build its new way of ruling the world. A good way of seeing it would be to admit that like Einstein's theory of relativity, science is as soft and uncertain as social sciences.
I believe there is a will to dominate by imposing a universalistic point of view to a subject genuinely submitted to particularistism.
I do not believe science can help choose a language for international communication. As large as the world is, I think it is unfair to assume there should be an international language. I believe there is nothing wrong with people learning several languages in order to communicate of larger territories.