I’ve been meaning to blog about Lonnie Thompson’s visit to Lamont last week; I suppose it’s the frigid temperatures here in New York that have kept melting tropical glaciers on my own back burner.
For those who don’t know, Lonnie Thompson runs the Ice Core Paleoclimatology Research Group at the Ohio State’s Byrd Polar Research Center. He’s a distinguished professor in OSU’s School of Earth Sciences, one of Time Magazine’s Heroes of the Environment, and the topic of Mark Bowen’s 2005 book, Thin Ice. He’s also spent more time above 18,000 feet than anyone, ever (Bowen 2005).
Thompson’s high-altitude adventures are all part of his efforts to create the world’s first tropical ice-core archive. Ice cores reveal information about past climates; by analyzing certain indicators (isotopic ratios and net mass accumulation, for instance), scientists are able to use ice cores to create high-resolution climate histories. Focusing on glacial ice in places like Kenya, Ecuador, and Tibet, Thompson and colleagues have collected more than 7,000 meters of ice and provided the world with centuries of annually resolved climatic data relevant to the regions where most of the world’s population lives.
The records are interesting on a number of levels. Thompson is able, for instance, to use ice core records to detail the connections between Peruvian glaciers and the tropical Pacific sea surface temperatures. He is also able to hypothesize about the speed at which several Andean glaciers were created, and to provide precipitation histories of the region that serves as the mouth of the Indus and Ganges rivers. Thompson also finds evidence of abrupt climatic change 5,200 years ago, an event that marks the transition from early Holocene warmth to cooler conditions.
Thompson’s data tells a more recent story as well. Temperature proxies (δ18O) in ice cores from tropical glaciers around the world show that low-latitude temperatures haven’t been as warm for at least two millennia. At the same time, Thompson finds that the percent of ice loss associated with current temperatures signals a recent and abrupt change in the Earth’s climate. Thompson believes that this, combined with evidence of an earlier abrupt transition, indicates that the present warming is unprecedented for at least 5,000 years.
One of the early pioneers of the field, Thompson certainly has a corner on information about tropical glaciers. But he’s not keeping it to himself, and his message is sobering. Unless we do something to slow climate change, melting glaciers might be just the tip of the iceberg.