Climatology (from Greek κλίμα, klima, "place, zone"; and -λογία, -logia) or climate science is the scientific study of climate, scientifically defined as weather conditions averaged over a period of time.[1] This modern field of study is regarded as a branch of the atmospheric sciences and a subfield of physical geography, which is one of the Earth sciences. Climatology now includes aspects of oceanography and biogeochemistry.
The main methods employed by climatologists are the analysis of observations and modelling the physical laws that determine the climate. The main topics of research are the study of climate variability, mechanisms of climate changes and modern climate change. Basic knowledge of climate can be used within shorter term weather forecasting, for instance about climatic cycles such as the El Niño–Southern Oscillation (ENSO), the Madden–Julian oscillation (MJO), the North Atlantic oscillation (NAO), the Arctic oscillation (AO), the Pacific decadal oscillation (PDO), and the Interdecadal Pacific Oscillation (IPO).