Warm Nights Could Cause More Carbon to be Released

The warming effects of climate change usually conjure up ideas of parched and barren landscapes broiling in a blazing sun, its heat amplified by greenhouse gases. But a study led by Princeton University researchers suggests that hotter nights may actually wield much greater influence over the planet's atmosphere as global temperatures rise -- and could eventually lead to more carbon flooding the atmosphere.

Since measurements began in 1959, nighttime temperatures in the tropics have had a strong influence over year-to-year shifts in the land's carbon-storage capacity, or "sink," the researchers report in the journal Proceedings of the National Academy of Sciences. Earth's ecosystems absorb about a quarter of carbon from the atmosphere, and tropical forests account for about one-third of land-based plant productivity.

During the past 50 years, the land-based carbon sink's "interannual variability" has grown by 50 to 100 percent, the researchers found. The researchers used climate- and satellite-imaging data to determine which of various climate factors -- including rainfall, drought and daytime temperatures -- had the most effect on the carbon sink's swings. They found the strongest association with variations in tropical nighttime temperatures, which have risen by about 0.6 degrees Celsius (33 degrees Fahrenheit) since 1959.

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