October 10, 2016--Nevada caves illuminate past climate, future challenges in the Southwest (Las Vegas Sun)

On a trip to Great Basin National Park, UNLV geoscience professor Matt Lachniet says that rainfall many millennia ago formed lakes in the desolate basins lining this strip of rural highway. Between the towns of Pioche and Panaca, we stop at Cathedral Gorge, where a multimillion-year dance of erosion and tectonics forged a slender canyon fringed with clay-colored spires. Closer to Great Basin, Lachniet’s grad student cuts left off an access road, down a 20-foot slope to an unspectacular oval-shaped depression in the land. This thirsty patch of earth was a lake 12,000 years ago, its ridges still marked by the force of ancient waves. “This is like a van Gogh painting to me,” Lachniet says. Water’s past forms the foundation of his research, including his climate studies inside Nevada caves. On a hot September day at his UNLV lab, he’d explained why, pointing to a table holding dozens of bisected stalagmites, the spikes that ascend against gravity from a cave’s floor. The delicate lines in the stone resemble tree rings. Cut a stalagmite in half, Lachniet said, and you find layers dating thousands of years, the echo of minerals left behind by water. 

For a climate scientist, these imprints are invaluable. Lachniet can track regional trends over 175,000 years, and researchers elsewhere have worked with much older samples. His focus is the long-term, looking at natural controls like gradual shifts in Earth’s orbit. On a time scale of years and decades, climate also is determined by sea-surface temperature, including El Niño patterns. That dynamic is changing with a modern variable: the politically thorny issue of global warming. While lawmakers debate, scientists agree that human activity exerts a strong force on the planet, a force so strong that when it comes to temperature, the natural climate machinery is often superseded by human-caused change, which has contributed to drought, rising sea levels and glacial retreat. Climate is a natural, cyclical process, skeptics say. True, but that scientific reality falls flat as an argument when you consider that humans can affect all sorts of natural processes. Just as the U.S. Geological Survey has shown human activity can induce earthquakes, NASA has shown that humans have rapidly affected the climate, with heat-trapping carbon at its highest level in 400,000 years. Using the cave records, Lachniet found that Nevada’s climate fluctuates between dry and wet in one cycle of about 21,000 years. Around 1,600 years ago, we entered a warming period and will continue trending drier. Add human activity, and Lachniet warns of a potential double-whammy. “There’s going to be the natural trend of warming plus the human trend on top of it. We could potentially expect faster rates of what will be normal due to human influence.” To view the full article visit the Las Vegas Sun.