New data published by the Met Office's Hadley research centre suggests that flooding will be an even bigger problem than anticipated for our warming planet. And it is plants that are to blame.
According to research, published in the journal Nature, plants tend to absorb and so expire less water from the soil when they grow in an atmosphere with high levels of CO2. This means the ground will become saturated, increasing the amount of water running off into rivers, making flooding more likely.
"It's a double-edged sword," said Dr Richard Betts, climate impact scientist at Hadley, and lead author of the study. "It means that increases in drought due to climate change could be less severe as plants lose less water. On the other hand, if the land is saturated more often, you might expect that intense rainfall events are more likely to cause flooding."
Plants matter to climatologists because of their place in the carbon cycle: through tiny pores on their leaves, known as stomata, they pull carbon from the atmosphere, in the form of carbon dioxide, and turn it into leaves and stalks and so on, drawing water in through their roots. Any excess water is expelled through these same pores, but in a CO2 rich atmosphere, the stomata close up slightly, making them less efficient evaporators.
Dr. Bets also notes that this work means it is not possible to draw like-for-like comparisons between CO2 and other greenhouse gases, such as methane, because of the additional direct impact carbon has on plants. ®