Large scale migration is always problematic. Those with places on the lifeboat will always tend to oppose taking others aboard. Often the tendency is strongest among those who have recently secured a place on board.
Much better to do what we can to minimize the need for migration. There are three different problems that we'll need to address:
- Lowland flooding from sea level rise;
- Climate shift -- the poleward movement of climate zones and changes in long-term average climate conditions affecting agriculture;
- Extreme weather events. Extreme heat waves, extreme rainfall events with flash flooding, and extreme cold snaps. These are associated with looser confinement of the polar vortex and wider meandering of the jet stream.
There's not much that can be done about rising sea levels. In some cases, dikes can be built to protect large areas of lowland, a' la the Netherlands in Europe. But in other cases, dike building is useless, because the coastal region overlies porous limestone. Seawater will just seep under any dikes built. That's the case in Florida, for example. In those cases, the only option is to artificially raise the land and buildings. That's possible, but expensive. It's already happening to a degree in Miami.
Climate shift exacerbates problems with crop failures, tree die-offs and forest fires, and with invasive insects and new diseases. Not much that can be done toward large-scale mitigation, but accelerating the shift toward indoor farming will help.
Extreme weather events are causing the biggest problems recently. The catastrophic flooding in Pakistan, torrential rain storms and flash flooding in much of the U.S. and Europe, deadly heat waves and deadly cold spells are all examples. One may deny that these result from climate change, since incidents of extreme weather events have occurred throughout history. It's the frequency and average severity of the incidents that are on the rise. Climate models predict that the rise will continue, and they show us why. There are reasonable mitigation measures that can be taken. Starting with "passive air conditioning" for heat waves.
During a recent heat wave in Texas, tens of thousands of cattle and other unprotected farm animals died of heat stroke. In India, it's been unprotected human beings, and not just farm animals, who have been dying.
There's a reasonably cheap, semi low-tech solution for that problem: "cold tents". There are recently developed paints that are super-reflective in visible and near-infrared wavelengths, while being efficient emitters of thermal infrared. If a mesh canopy with such paint on its top side is spread over a region of land, the partially shaded land below the canopy will be cooled below ambient air temperature. There is no power consumed, and I believe the cost of land coverage can be on the order of a dollar per square meter. $10,000 per hectare. That's a non-trivial expense, but cheap for a life-saving shelter from intense heat.