El Nino May Slow Global Warming, Study Says
Finally, someone has something nice to say about El Nino.
Researchers from the National Oceanic and Atmospheric Administration found that from 1991 to 1994 - years when El Nino warmed the Pacific - the ocean released 30 percent to 80 percent less carbon dioxide, a gas that is believed to trap heat in the atmosphere.
The finding was published in today's issue of the journal Nature.
Scientists commonly estimate how much carbon dioxide should be in the atmosphere by calculating how much fossil fuel is burned. But some 2 billion tons of carbon dioxide go unaccounted for each year.
According to the NOAA research, reduced carbon-dioxide releases in the Pacific during El Nino could account for about 16 percent to 36 percent of this "missing" gas.
"Obviously, we are very, very interested in where the CO2, which we are releasing every year during fossil fuel burning, ends up," said Rik Wanninkhof, an NOAA oceanographer.
Understanding the year-to-year changes in carbon dioxide levels is key to explaining how the oceans, the land and the atmosphere regulate Earth's climate.
Carbon-dioxide levels in the atmosphere have been rising for decades, a phenomenon blamed on increased burning of fossil fuels and deforestation. Some scientists say this has contributed to global warming .
Previously, episodes of El Nino - the naturally occurring, cyclical warming of the Pacific - were shown to spur plant growth, which in turn sucks carbon dioxide out of the atmosphere. The NOAA research shows another way El Nino helps reduce carbon-dioxide levels.
Usually, the equatorial waters of the Pacific are the source of three-quarters of the carbon dioxide released by the world's tropical oceans. The northern Pacific sucks up all of that and more each year, making it one of the biggest "carbon sinks."
El Nino intensifies that process: The trade winds along the equator die down, so the upwelling of cold, carbon-rich waters decreases and less carbon dioxide is sent into the atmosphere.