This document provides supplementary information for the CRU TS3.10 paper, including web links to data sources, detailed updates for specific variables, and analyses of the impact of using a wind climatology in PET calculations. It covers: 1. **Web Links**: Provides links to various climate data sources, such as MCDW bulletins, CLIMAT reports, and temperature series from different countries. 2. **Detailed Information on Variable Updates**: - **Mean Temperature (TMP)**: Updates are made through CLIMAT, MCDW, and WWR, reducing missing values from 38% to 34%. - **Mean Monthly Maximum and Minimum Temperature (TMX/TMN)**: New data sources include NOAA/NCDC, CLIMAT, Canadian homogenized series, and Australian archives. - **Monthly Total Precipitation (PRE)**: Additional sources include NCDC, WWR, ASEAN Compendium, and Iranian climate data. - **Monthly Counts of Rain-Days (WET)**: Conversion factors from RDY to RD0 were derived to improve coverage. - **Mean Monthly Vapour Pressure (VAP) and Monthly Total of Sun-hours (SUNH)**: Updates are made using CLIMAT and MCDW monthly publications. 3. **Use of a Wind Climatology in Calculating PET**: A 1961-1990 wind speed climatology is used due to insufficient monthly wind observations. Comparisons show good agreement with published PET series. 4. **Trend Analysis and Comparisons**: Trends for TMP (using CRUTEM4) and PRE (using GPCCv5) are analyzed over three time periods (1901-1950, 1951-2009, and 1901-2009). Confidence limits and autocorrelation adjustments are used to determine significant trends and their consistency. The document aims to provide comprehensive background and supporting evidence for the CRU TS3.10 dataset, enhancing its reliability and usability.This document provides supplementary information for the CRU TS3.10 paper, including web links to data sources, detailed updates for specific variables, and analyses of the impact of using a wind climatology in PET calculations. It covers: 1. **Web Links**: Provides links to various climate data sources, such as MCDW bulletins, CLIMAT reports, and temperature series from different countries. 2. **Detailed Information on Variable Updates**: - **Mean Temperature (TMP)**: Updates are made through CLIMAT, MCDW, and WWR, reducing missing values from 38% to 34%. - **Mean Monthly Maximum and Minimum Temperature (TMX/TMN)**: New data sources include NOAA/NCDC, CLIMAT, Canadian homogenized series, and Australian archives. - **Monthly Total Precipitation (PRE)**: Additional sources include NCDC, WWR, ASEAN Compendium, and Iranian climate data. - **Monthly Counts of Rain-Days (WET)**: Conversion factors from RDY to RD0 were derived to improve coverage. - **Mean Monthly Vapour Pressure (VAP) and Monthly Total of Sun-hours (SUNH)**: Updates are made using CLIMAT and MCDW monthly publications. 3. **Use of a Wind Climatology in Calculating PET**: A 1961-1990 wind speed climatology is used due to insufficient monthly wind observations. Comparisons show good agreement with published PET series. 4. **Trend Analysis and Comparisons**: Trends for TMP (using CRUTEM4) and PRE (using GPCCv5) are analyzed over three time periods (1901-1950, 1951-2009, and 1901-2009). Confidence limits and autocorrelation adjustments are used to determine significant trends and their consistency. The document aims to provide comprehensive background and supporting evidence for the CRU TS3.10 dataset, enhancing its reliability and usability.