Deciphering recent climate change in central Mexican lake records

Central Mexico contains a large number of lake basins offering opportunities for climatic reconstruction. The area has, however, also been the focus for human settlement since the time of the earliest occupation of the Americas, as well as being subject to tectonic and volcanic activity. A number of methodological issues arise including the susceptibility of common palaeoecological proxies (pollen, diatoms) to multiple forcing factors and problems of obtaining reliable chronologies. Published lake records indicate that the last 1,500 years have been marked by strong climatic variability, superimposed on continuing high levels of anthropogenic impact. Dry conditions, probably the driest of the Holocene, are recorded over the period 1400 to 800 14C yr BP (ca. AD 700–1200). Climatic change over the last 1,000 years is not well represented, but there are indications of drier conditions corresponding to the ‘Little Ice Age’ of mid- to high latitudes. A range of mechanisms (e.g. solar cycles, ENSO variability) have been proposed to explain climatic variability over the last 1,500 years, but current lake records are inadequate to test these. The developing dendroclimatology for the Mexican highlands and the rich historical archives of the Hispanic period (from AD 1521) offer new opportunities and challenges to palaeolimnologists.