Lascar Volcano (Chile) erupted on 20 July 2000, generating a >10 km high ash column. Satellite infrared data have previously indicated that Lascar's large vulcanian explosions are preceded by significant cooling within the active crater, suggesting that characteristic thermal radiance trends can act as remotely detectable eruption precursors. New analyses and data extend the Lascar's thermal history to cover all five large vulcanian eruptions occurring over the last 15 years. The 2000 eruption follows a formerly undocumented style of infrared radiance variation and indicates that Lascar may have modified its activity since 1993, the year of its greatest historical eruption. Therefore such patterns, evident for over a decade at Lascar, can be unexpectedly modified and this has implications for the way apparent thermal precursors should be treated. The largest 1993 eruption produced 8.5 km long pyroclastic flows which the infrared data indicate exhibited exponential cooling over an 8--12 months period. ¿ 2001 American Geophysical Union