Discover aliens, as I reckon finding alien life would be a big step forward in helping humanity unite as one race. Also, if it's intelligent life they might be able to share some cool new technology with us. Amplified senses would mostly be annoying and uncomfortable. I have no need to master one fighting style, never mind all of them. Everything that's happened in the history of our timeline has led to now, changing any of it might not work out too well. I don't care what's in Area 51, it's probably just some secret but boring military stuff. Knowing how the world will end would be depressing. Whilst reversing global warming would initially be a positive, chances are we'd then just carry on doing what we're doing now and be back in the same situation before too long. Also aliens might help us sort it out properly.