Two summers ago, Switzerland saw its hottest June in 250 years. Then, in August of that year, temperatures in France soared to 40°C (104°F) and remained high for weeks. Scientists estimate that more than 30,000 Europeans, many of them French, died during that heat wave (SN: 7/3/04, p. 10: Available to subscribers Dead Heat).
Now, new climate research shows that the hot, dry weather affected more than the continent’s people. Data from satellite-borne sensors measuring reflected light from foliage suggest that plants in the region sported as little as two-thirds as much greenery in 2003 as they did on average in the 3 previous years, says Philippe Ciais of the Laboratory for Climate Sciences and the Environment in Gif-sur-Yvette, France. The largest decreases in foliage occurred in France and northern Italy.
Leaves extract carbon dioxide from the atmosphere, and ground-level measurements during the heat wave indicated higher-than-normal amounts of the gas across Europe, says Ciais. He and his colleagues conclude that plants stressed by the heat and drought were taking up much less carbon dioxide than they had in previous years.
As a whole, European plants probably produced about 30 percent less greenery and, as a result, absorbed about 1.8 billion metric tons less carbon dioxide than they had in previous years, the researchers conclude in the Sept. 22 Nature.