title: Abrupt tropical climate change: past and present.
abstract: Three lines of evidence for abrupt tropical climate change, both past and present, are presented. First, annually and decadally averaged delta(18)O and net mass-balance histories for the last 400 and 2,000 yr, respectively, demonstrate that the current warming at high elevations in the mid- to low latitudes is unprecedented for at least the last 2 millennia. Second, the continuing retreat of most mid- to low-latitude glaciers, many having persisted for thousands of years, signals a recent and abrupt change in the Earth's climate system. Finally, rooted, soft-bodied wetland plants, now exposed along the margins as the Quelccaya ice cap (Peru) retreats, have been radiocarbon dated and, when coupled with other widespread proxy evidence, provide strong evidence for an abrupt mid-Holocene climate event that marked the transition from early Holocene (pre-5,000-yr-B.P.) conditions to cooler, late Holocene (post-5,000-yr-B.P.) conditions. This abrupt event, approximately 5,200 yr ago, was widespread and spatially coherent through much of the tropics and was coincident with structural changes in several civilizations. These three lines of evidence argue that the present warming and associated glacier retreat are unprecedented in some areas for at least 5,200 yr. The ongoing global-scale, rapid retreat of mountain glaciers is not only contributing to global sea-level rise but also threatening freshwater supplies in many of the world's most populous regions.
authors.affiliation: Byrd Polar Research Center and Departments of Geological Sciences and Geography, Ohio State University, Columbus, OH 43210, USA. thompson.3@osu.edu
authors.forename: Lonnie G
authors.initials: LG
authors.lastname: Thompson
authors.forename: Ellen
authors.initials: E
authors.lastname: Mosley-Thompson
authors.forename: Henry
authors.initials: H
authors.lastname: Brecher
authors.forename: Mary
authors.initials: M
authors.lastname: Davis
authors.forename: Blanca
authors.initials: B
authors.lastname: León
authors.forename: Don
authors.initials: D
authors.lastname: Les
authors.forename: Ping-Nan
authors.initials: PN
authors.lastname: Lin
authors.forename: Tracy
authors.initials: T
authors.lastname: Mashiotta
authors.forename: Keith
authors.initials: K
authors.lastname: Mountain
mesh_terms: D017752:Greenhouse Effect; D006801:Humans; D019021:Natural History; D014329:Tropical Climate