In my final journalistic piece to appear in 2008, I covered the scariest news I heard all year, namely that the pH of the oceans is decreasing a lot faster than expected, due to all that CO2 we put into the air. One of the papers that came out in December in PNAS quantifies the trend as 0.04 units per year, which would mean a whole unit in around 25 years. As the pH is a logarithmic scale, that would mean 10 times more H+ ions in the oceans, and it would turn the entire marine biosphere upside down.
Current Biology 18, No 24 (23.12.), R1112
Abstract and restricted access to full text here.