The reconstruction of the dynamic elements of past environments is extremely important for understanding both the present state and evolutionary trends in future climate development. Since long-term measurements on climate variability very rarely go back more than about 100 years, palaeoclimate and environmental reconstructions based on proxy indicators must be used to validate the output of global climate models. Especially important such reconstructions are in climatologically sensitive and pristine regions such as polar areas, where any small global climate change results in distinct regional variations of temperature, precipitation, and other climate-induced changes. There are few examples of quantitative palaeoclimate studies in Siberia. The obtained environmental reconstructions have to be tested by further quantitative studies from other sites in this region, using numerical proxy data that are based on regional calibration datasets and temperature models, which were not available until now. At the present state of knowledge, biological indicators from aquatic and terrestrial environments are the most reliable proxies, because they react sensitively to climate change and define different aspects of environments, which should be assessed together for reliable reconstructions. The basis of all quantitative reconstruction approaches are regional calibration datasets from which the empirical reconstruction models (i.e. the transfer function) will be established. New calibration dataset and based on it chironomid-climate inference models for reconstructing palaeoclimate variables were established along latitudinal temperature gradients in northeastern Siberia. Previous application of non-regional models for temperature reconstruction causes difficulty in their interpretation and makes results sometimes controversial. Reconstructions of the ecological conditions of the Holocene were made using the new models and have shown fluctuations in the lake level and other climate dependant parameters. Strong faunistic changes take place after 4500 yBP. T july went down up to 2oC below modern temperature. These observations confirm end of Holocene climate optimum at this time.