Tim McDonnell

Tim McDonnell

Climate Desk Associate Producer

Tim McDonnell joined Climate Desk after stints at Mother Jones and Sierra magazine. He remains a cheerful guy despite covering climate change all the time. Originally from Tucson, Tim loves tortillas and epic walks.

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Slicing Open Stalagmites to Reveal Climate Secrets

| Thu Jun. 6, 2013 3:04 PM EDT

Stacy Carolin collects samples in a Borneo cave last fall.

If you've ever visited a cave, you know the rules: Stay on the path, and keep your greasy paws off the formations. So Stacy Carolin was a bit taken aback the first time she headed into a cave not as a tourist, but as a scientist, and took a step off the beaten path. "I was a city girl back then," she recalls. "It was very muddy and slippery…and also completely pitch black." Not exactly the setting you'd expect for cutting-edge climate change research.

A few years later, Carolin, a Ph.D. student at Georgia Tech, is breaking ground in the field of paleoclimatology, the study of ancient climates, using an unconventional but increasingly prevalent tool: speleothems, a catch-all term for cave formations that includes stalagmites (remember the mnemonic: those that "mite" reach the ceiling from the floor) and stalactites (those that hold "tite" to the ceiling).

In a study released today in the journal Science, Carolin and her colleagues outline 100,000-year-old rainfall conditions in Borneo, mapped from chemical clues in cave formations there. Like most historic climate reconstructions, the goal is to compile real-life data against which to test predictive models; if scientists know how much rainfall there was in the tropics in the past, they can see how well their models are able to replicate those conditions, and tweak accordingly. But the most commonly-used "proxies" for ancient climates, including tree rings and ice cores, are notoriously inadequate in the tropics, leaving holes in scientists' geographic picture of the past and making it difficult to measure historic changes in tropical weather systems, like monsoons, which can themselves have major impacts on global climate.

Deep inside caves in Mexico, Southeast Asia, China, and other limestone-rich locales worldwide, scientists have found rich troves of data in speleothems. Researchers look for formations that have already fallen over or broken off, so as not to damage the cave, haul these back to the lab, slice them open ("like a hot dog," Carolin says), and study the ancient atoms within to discover how old they are and how much rainfall there was at different points in their past (speleothems form when rainwater drips through the limestone, picking up acid and minerals that pile up in the cave).

Tim McDonnell

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Which States Use the Most Green Energy?

| Thu May 16, 2013 5:00 AM EDT

Florida and Texas might be leading the nation's rollout of solar and wind power, respectively, but Washington, where hydroelectric dams provide over 60 percent of the state's energy, was the country's biggest user of renewable power in 2011, according to new statistics released last week by the federal Energy Information Administration.

Hydro continued to be the overwhelmingly dominant source of renewable power consumed nationwide, accounting for 67 percent of the total, followed by wind with 25 percent, geothermal with 4.5 percent, and solar with 3.5 percent. The new EIA data is the latest official snapshot of how states nationwide make use of renewable power, from industrial-scale generation to rooftop solar panels, and reveals an incredible gulf between leaders like Washington, California, and Oregon, and states like Rhode Island and Mississippi that use hardly any.

The gap is partly explained by the relative size of states' energy markets, but not entirely: Washington uses less power overall than New York, for example, but far outstrips it on renewables (the exact proportions won't be available until EIA releases total state consumption figures later this month). Still, the actual availability of resources—how much sun shines or wind blows—is far less important than the marching orders passed down from statehouses to electric utilities, says Rhone Resch, head of the Solar Energy Industries Association.

"Without some carrot or stick, there's little reason to pick [renewables] up" in many states, he says; even given the quickly falling price of clean-energy technology, natural gas made cheap by fracking is still an attractive option for many utilities.

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