ABOUT 183 million years ago, during the Jurassic, something prompted a massive growth of ocean algae. Now evidence suggests that the trigger was a vast amount of carbon dioxide released into the atmosphere by the heating of coal deposits.
Jennifer McElwain of the Field Museum in Chicago and her team discovered there must have been excess CO2 in the atmosphere at the time by studying the CO2– absorbing pores or stomata of fossil leaves: the fewer the stomata, the more readily CO2 must have been available.
To account for the excess CO2, the team studied…
