Orlando Sentinel: Homo sapiens faces a crucial test. Can we swiftly reverse the global overheating and climate instability that we have caused? Our future may depend on passing this test. Signs that humanity’s reckless greenhouse-gas emissions have overheated and destabilized the climate are unmistakable. This year is headed toward the highest average global temperature in 130 years. Weather extremes have become more frequent this decade with fierce storms, killer cold, killer heat waves, lethal floods …