Abstract High-elevation tropical glaciers provide records of past climate from which current changes can be assessed. Comparisons among three ice-core records from tropical mountains on opposite sides of the Pacific Ocean reveal how climatic events are linked through large-scale processes such as El Niño–Southern Oscillation. Two distinctive trans-Pacific events in the mid-fourteenth and late-eighteenth centuries are distinguished by elevated aerosol concentrations in cores from the Peruvian Andes and the Tibetan Himalaya. Today aerosol sources for these areas are enhanced by droughts accompanying El Niños. In both locations, large-scale atmospheric circulation supports aerosol transport from likely source regions. Oxygen isotopic ratios from the ice cores are significantly linked with tropical Pacific sea-surface temperatures, especially in the NIÑO3.4 region. The arid periods in the fourteenth and eighteenth centuries reflect droughts that were possibly connected to strong and/or persistent El Niño conditions and Intertropical Convergence Zone migration. These ‘black swans’ are contemporaneous with climate-related population disruptions. Recent warming, particularly at high elevations, is posing a threat to tropical glaciers, many of which have been retreating at unprecedented rates over the last several thousand years. The diminishing ice in these alpine regions endangers water resources for populations in South Asia and South America.

The potential of stable isotopic ratios ( 18 O/ 16 O and 2 H/ 1 H) in mid- to low-latitude glaciers as a modern tool for paleoclimate reconstruction is reviewed. To interpret quantitatively the ice-core isotopic records, the response of the isotopic composition of precipitation to long-term fluctuations of key climatic parameters (temperature, precipitation amount, relative humidity) over the given area should be known. Furthermore, it is important to establish the transfer functions that relate the climate-induced changes of the isotopic composition of precipitation to the isotope record preserved in the glacier. This paper will present long-term perspectives of isotopic composition variations in ice cores spanning the last 25,000 years from the mid- to low-latitude glaciers. The δ 18 O records from the far western Tibetan Plateau suggest temperatures as warm as today occurred approximately 3000 years ago. However, δ 18 O records from the Himalayas and the eastern side of the Tibetan Plateau confirm that the twentieth century is the warmest period in the last 12,000 years. In the South American Andes on Huascarán, δ 18 O records suggest temperatures as warm as those of today occurred 5000 years ago. All the tropical glaciers for which data exist are disappearing. The evidence for recent and rapid warming in the low latitudes is presented and possible reasons for this warming are examined. The isotopic composition of precipitation should be viewed not only as a powerful proxy indicator of climate, but also as an additional parameter for understanding climate-induced changes in the water cycle, on both regional and global scales.