Though it's true many people were skeptical about an AI winning at Go played at this level, I think people are mostly skeptical about general AI, not about algorithms that win at playing board games. It's different to be skeptical about specialized AI than about general AI.
General AI could be the biggest ever discovery for humanity. But it will never be if we don't put a hard enough effort. The bad thing, is that economy laws seem to assign a limited effort toward it. In my opinion we should be trying harder. Worth mentioning is OpenAI (https://openai.com/), an effort by Y Combinator, Elon Musk and others. Brilliant initiative.
Overpopulation in terms of running out of space is definitely overplayed. But it's a direct multiplier for our effect on the environment. If the world's population were cut in half, we'd emit about half as much pollution, half as much greenhouse gas, half the land used for farming would be left wild, etc.
Not necessarily...carbon emissions per capita is not constant around the globe. Energy use is skewed towards modern countries, i.e United States. If you wiped out the 300 million people in the US, you would save more on carbon emissions than wiping out 300 million in China.
