Freshwaters in dierent regions show many similarities and dierences in their responses to climatic warming. Bases for comparison include reports from regional committees, long-term records for several sites where climate has warmed in the past two decades and other human alterations to freshwaters that simulate some of the expected results of climatic warming, such as reservoir construction. Palaeoecological studies of freshwaters under climatic warming and dierences in communities under dierent climatic regimes are also considered. Major changes in the physical, chemical and biological characteristics of lakes occur. Many of the changes to lakes and streams are the result of strong eects of climatic warming on terrestrial catchments. Inputs from catchments can be either dampened or ampliยฎed by in-lake processes, in some cases causing counter-intuitive responses, such as the acidiยฎcation of streams but alkalinization of lakes in areas where supplies of base cations are limited. Consideration of landยฑwater interactions and interactions between climatic warming and other human stresses are important for the accurate prediction of the eects of climatic change.