Your can't know that, there's too many variables. Let's assume a terrible scenario with massive heatwaves across the Middle East and Central and Southern Asia (like the ones that have already happened, including recently, in Iraq and and India) that get too frequent and unbearable. Add in food supply problems due to droughts, fertilizer shortages, etc. Now you have millions of migrants going to Europe , or at least North. No one can reliably predict how such a scenario plays out, migrant crisis are unpredictable.
