A raging dispute among climate scientists is breaking into the open. Could they slow global warming by injecting aerosols into the atmosphere to reflect sunlight, or are the unintended consequences potentially so dangerous that even experimentation should be prohibited? The very idea was beyond the pale at the time of the Paris Agreement, but now it's gaining some traction. Opponents say it's beyond reckless. Would trying to resolve one problem create others that could get out of control?