 Homogenization is necessary for all climate data to correct for non-climatic changes, such as introduction of different measurement instruments, changes in location of the instruments, or differences in the time of day that measurements are taken.The NOAA temperature dataset is regularly updated with refinements improving the allowance for known biases, including the effects of past changes in methods of collecting temperatures.In 2015 it changed from the Global Historical Climatology Network to the new International Surface Temperature Initiative databank which includes many more stations giving wider coverage of land surface temperatures, and the latest Extended Reconstructed Sea Surface Temperature dataset (version 4) which made improved allowances for biases, including the phased changeover from measuring ship water intake to using automatic buoys