My own approach is to show pictures of hospitals during the 2003
European killer heat wave and pictures of hurricane Katrina submergence and refugees, and to say that it is highly likely that there will be many more such scenes in the future (that is, scenes of mortality, flooding and environmental refugees), due to the probable increase in heat waves and flooding.
Here are some that come to mind: the
European heat wave that killed at least 50,000 people in 2003, the Russian
killer heat wave in 2010 and Pakistan flooding in the same year.