Have you considered purchasing carbon offsets for airplane trips or other activities that generate carbon? Do you ever wonder if they make a difference, or how you can make sure they do offset carbon as advertised? Should you choose tree planting or energy retrofits, for example? (Energy retrofits are recommended because of their immediate and long lasting impact.) This short video, from MIT, provides a great explanation of what carbon offsets are, what net zero means, and how to choose offsets that will have an environmental benefit.