Can scientists use global temperature data as is?

No. The Goddard Institute for Space Studies (GISS) utilizes temperature data for conducting long-term climate studies. To ensure the reliability of station data for such research, it's crucial that the time series of observations are consistent. GISS also needs to eliminate any temperature fluctuations that are not caused by climate-related factors. These fluctuations can occur due to station relocations, equipment updates, or the merging of data from various sources into a single dataset.

Originally, only documented cases were adjusted, however the current procedure used by NOAA/NCEI applies an automated system that uses systematic comparisons with neighboring stations to deal with documented and undocumented instances of artificial changes. The processes and evaluation of these procedures are described in numerous publications — for instance, Menne et al., 2018 and Venema et al., 2012 — and at the NOAA/NCEI website. Uncertainty arising from the statistical method used to remove artificial changes is accounted for in the confidence interval on the global mean.

For more information, visit: https://climate.nasa.gov/blog/3071/the-raw-truth-on-global-temperature-records/.