When I wrote a few weeks ago about EPA's first baby step towards slowing climate change--a proposed limit on CO2 emissions from new coal-fired power plants--I didn't expect to see new evidence of global warming so soon thereafter. I say "evidence" rather than "proof" because the weather is too variable to draw strong conclusions from any single event.
Nonetheless, the recent weather patterns are too extraordinary to be ignored. Locally, DC recorded 11 straight days of 95-plus temperatures, three days longer than the previous record. Moreover, the three previous occurrences of 8-day streaks all occurred since 1987.
Most of us probably had never heard of a "derecho", because they usually only occur out west, until one swept through this area on June 29 and knocked out power for millions of people.
Nationally, 3,215 daily high temperature records were set in June throughout the United States, and NOAA has reported that the last six-month and 12-month periods were the warmest on record. And the severe drought that is affecting more than half of the country is the worst in more than half a century. One consequence has been the terrible fires in Colorado, where hot, dry weather has made the forests more vulnerable to burning. The map, from earthobservatory.nasa.gov, shows the drought effects--brown means vegetation is less than normal, green means more than normal.
NASA just announced that polar sea ice coverage in June was the lowest ever recorded, breaking the record set just two years ago. And as the ice shrinks, warming accelerates--sea ice reflects 90 percent of solar heat back into space but open sea water absorbs 90 percent of that heat.
While we can't be 100 percent certain that the warming is due to human activity, it is by far the most likely explanation. Scientists knew in the 19th century that CO2 was a greenhouse gas. Since then the amount of CO2 in the atmosphere has gone up 40 percent--from 280 ppm to 392. It is still going up about two ppm annually and this rise is entirely due to human activity, mainly burning of fossil fuels.
CO2 also has other harmful effects. Marine scientists estimate that all of the world's coral reefs--which play a critical role in sustaining ocean life--will be gone within a generation because CO2 is making the water more acidic, and coral can survive only within a narrow pH range.
In short, Mother Nature is sending all kinds of warning signals that something bad is happening. It's time to start listening.