Upon retiring in April after more than four decades as a NASA climate scientist, Dr. James Hansen told Columbia University students he feared “climate chaos” if we do not act immediately to curb greenhouse gas emissions. There are now more than 800 natural disasters worldwide annually, according to the reinsurance giant Munich Re, double the number 20 years ago. That may just be the beginning. The number could skyrocket to 15,000 disasters per year by 2030, said General Electric’s global strategy director Peter Evans, meaning mile-wide tornados like the one that devastated Moore, Oklahoma in May would be the norm.