 Welcome back to NewsHour. Coming up, we'll be talking about the high stakes of President Biden's solo news conference at the NATO summit tonight. Some commentators are even saying it's make or break in terms of his plan to stand as presidential candidate this autumn. And we have a good news story from China about reducing greenhouse gas emissions. But first, Nigeria is Africa's economic powerhouse. So why are so many young people trying to leave the country? It's become so common.