 Imagine California in 2040. The kind of weather that leads to extreme fires is 20% more common than it is today. In central Texas, corn and soybean crop yields are down by more than two-thirds. Hurricanes continue to ravage southern Louisiana, and more than 40 days a year are too hot and humid to work outside or exercise safely. Climate change is beginning to transform the lives of millions of Americans, and it has arrived on my doorstep in Northern California, too. For two years, I've been studying how climate change will force a large new global migration. For 6,000 years, these regions in North America are where temperature and precipitation have been most suitable for human survival. Researchers project that even with moderate carbon emissions, over the next 50 years, that niche zones will move north. If carbon emissions continue at a more extreme rate, the zone will move even farther north. But Americans have been moving in the opposite direction, to parts of the country with some of the most extreme climate dangers, like more and more days of scorching heat. Scientists have developed a range of different scenarios for how carbon emissions could affect our climate. If carbon emissions continue to grow sharply, we may see extreme levels of carbon concentration in our atmosphere. But climate change could be plenty devastating, even in the scenario where emissions grow at a more modest pace. The South and parts of the West will endure dramatic losses in agriculture production, with some counties in Texas suffering the worst. Warming temperatures could spur more production in northern states like Minnesota. Experts suggest Detroit, Buffalo, Milwaukee may see a renaissance, as climate migrants from the lower half of the country move north. Climate-driven economic damage will spread across the southern third of the country, erasing more than 8% of economic output. But it won't hit everyone equally. Rural, poor, black and indigenous communities in the south are likely to bear disproportionate pain. Where will people in rural parts of Louisiana go after the next hurricane? How will farm workers survive when crops have dried up? Who will have the means to move? And who will be trapped or left behind?