Plants put the brakes on global warming but clouds – sometimes suggested as a climate stabiliser – amplify it, scientists have shown this week. In the first case, NASA researchers have developed more detailed computer models of how plants respond to the increased amount of CO2 that humans are putting into the atmosphere. To do this, Lahouari Bounoua and his colleagues incorporated a previously-overlooked way in which plants grow more efficiently in these circumstances into their simulations.
When more CO2 is available, plants are able to use less water yet maintain previous levels of the photosynthesis process that drives their growth, in a process called “down-regulation”. Meanwhile, higher temperatures would increase leaf growth, and in turn raise the movement of water into the atmosphere from plants and land known as evapotranspiration on a global scale. Water cools surfaces it evaporates from, which is why we sweat, and so this creates an additional cooling effect. Consequently plants provide more help in keeping the Earth’s temperature down through “cooling feedbacks” in simulations including this process than existing models predicted. Read the rest of this entry »