Finding no coral bleaching over the past 150 years is hardly a conclusive finding. Climate has varied significantly since corals became the dominant reef builders in the ocean. I do not deny that human activity can and has damaged reefs—pollution and direct physical destruction has ravaged many ocean environments. However, I do not accept that variations in temperature and pH of an equal or greater magnitude than today have not occurred in the past. As the collection of climate data has improved, it has become obvious that temperature variation caused by the El Niño/La Niña cycle and other decade scale osculations dwarfs any warming trend due to human activity. One of the points of the paper I reviewed was that many corals are more resilient than the insanely fragile creatures usually portrayed by ecologists. Any life form that over specializes to the point where it cannot tolerate a few degrees of temperature change or other variation in its environment has evolved itself into extinction. And, as the long, brutal record of life on Earth shows, nature periodically cleans house, clearing away the over specialized to make way for new forms of life. Since coral is still around after several hundred million years and a number of notable extinction events, they must not be as delicate as generally thought. As a scuba diver, I am glad that they are tougher than assumed.