Abrupt Tropical Climate Change: Past and Present Lonnie Thompson, E Mosley-Thompson, H Brecher, M Davis, B Leon, D Les, P Lin, T Mashiotta, K Mountain David Chauvaux AtmosSci
An examination of three lines of evidence that point to multiple events of abrupt climate change in the last ~5000 years, possibly including now
1) δ18O averages and net mass-balance histories determined from ice cores covering the last 400 and 2000 years show that current warming of high elevations in the tropics is unprecedented in at least 2 millennia
2) The retreat of mid- to low-latitude glaciers (which had been doing just fine for thousands of years) signals a recent, abrupt change in Earth's climate
3) Carbon dating of preserved plants recently exposed along the margin of the Quelccaya ice cap as it recedes, along with widespread proxy evidence, point to an abrupt cooling event marking the transition from early to late Holocene ~5200 years ago
Where Oh Where Has My Glacier Gone? • Qori Kalis, outlet of Quelccaya, has been monitored since 1963 • Avg retreat rate 1963-1978: ~6m/yr • Avg retreat rate 1991-2005: ~60m/yr • 10X faster in only 30 years!!!
Graph shows about equal rates of retreat across numerous Peruvian glaciers • Avg retreat rates 1980-1995: ~20m/yr
400 years ago to now: Everybody Loves Ice Cores 2 sets of cores were takes from Quelccaya, in 1983 and 2003 Annual avg δ18O values were compared across the cores and found to be virtually identical Double significance • confirms time scale for 1983 core • shows that δ18O record well-preserved despite 20 yrs of surface warming
7 cores compared from Andes, Himalayas, and Tibetan Plateau to build a climate profile
The current accelerating glacial retreat across the world suggests the increase in the globally averaged temperature may have prematurely interrupted the natural progression of cooling. Observations suggest that a century of human activity may have kicked the global climate closer to what it had been like before 5000 years ago. If so, the retreat of the glaciers may indicate the passing of a threshold and tropical glaciers may soon disappear.
Movie time! https://www.youtube.com/watch?v=y0qDc4hXUSY