Ethically speaking, what should developed nations do to assist people living in, for example, sub-Saharan Africa, who have no resources with which to relocate,

Ethically speaking, what should developed nations do to assist people living in, for example, sub-Saharan Africa, who have no resources with which to relocate, and are already suffering the consequences of climate change? I consider it a catastrophic situation, even though I'm personally not among the sick, dying, or refugees. I don't think it's fear-mongering to acknowledge the massive harm industrial nations are causing to real human beings, and to demand solutions of policy-makers, even if those solutions are costly.