open borders  is justice, not charity . Saving perfect strangers  may be  a matter of charity. But letting strangers save themselves with the willing assistance of people other than yourself is a matter a justice .
This underscores the importance of why it won’t do, as Matt Ridley opined , to tell “the poor to give up the dream of getting richer through fossil fuels.” Taxing or regulating carbon emissions and subsidizing alternative energy sources in the hope of achieving a carbon-free economy will not allow us to deal with the possible consequences of global warming. Even the EPA says  that “if we stabilized concentrations and the composition of today’s atmosphere remained steady (which would require a dramatic reduction in current greenhouse gas emissions), surface air temperatures would continue to warm.” In other words, reducing carbon emissions won’t make much difference in global temperatures over the century, but it will seriously impede the poor getting richer.
Recent anthropological research  by Penn State University’s Pat Shipman, built on a complete sequencing of the Neanderthal genome, shows that Neanderthals survived many periods of abrupt climate change, including a “volcanic winter” caused by a massive eruption near what is now Naples. If they survived and adapted to abrupt climate change, surely modern man ought to be able to adapt to long-term changes, provided climate policies don’t stifle human progress and economic growth.