evidence: Data adjustments may also be required if there are changes to the time of day that observations are made. If, for example, a network of weather stations adopts a uniform observation time, as they did in the United States, stations making such a switch will see their data affected, because temperature is dependent on time of day. [...] While raw data from an individual station are never adjusted, any station showing abnormal data resulting from changes in measurement method, its immediate surroundings, or apparent errors, is compared to reference data from neighboring stations that have similar climate conditions in order to identify and remove abnormal data before they are input into the GISTEMP method. While such data adjustments can substantially impact some individual stations and small regions, they barely change any global average temperature trends. [...] Independent analyses conclude the impact of station temperature data adjustments is not very large. Upward adjustments of global temperature readings before 1950 have, in total, slightly reduced century-scale global temperature trends. Since 1950, however, adjustments to input data have slightly increased the rate of global warming recorded by the temperature record by less than 0.1 degree Celsius (less than 0.2 degrees Fahrenheit).