Sugar maples are flowering! These off years when they do, they unfurl countless millions of ethereal dangling blooms all over New England. In Montpelier this happened during recent rains, but on the uplands around town they are blooming still, the palest of greens and full of movement and light, nascent leaves opening above them. Now something truly amazing happens. The carbon dioxide buildup in our hemisphere starts to drop. By July 1, maples and others will be transforming their blooms into seed for the next generation, and carbon dioxide levels will be markedly lower, compliments of photosynthesis. Then back again next winter, thanks to human activity.