Urbanization bias III. Estimating the extent of bias in the Historical Climatology Network datasets - Supplementary Information

Supplementary information dataset for the following article: R. Connolly and M. Connolly (2014). Urbanization bias III. Estimating the extent of bias in the Historical Climatology Network datasets. Open Peer Rev. J., 34 (Clim. Sci.), ver 0.1 (non peer-reviewed draft) Abstract of article The extent to which two widely-used monthly temperature datasets are affected by urbanization bias was considered. These were the Global Historical Climatology Network (GHCN) and the United States Historical Climatology Network (USHCN). These datasets are currently the main data sources used to construct the various weather station-based global temperature trend estimates. Although the global network nominally contains temperature records for a large number of rural stations, most of these records are quite short, or are missing large periods of data. Only eight of the records with data for at least 95 of the last 100 years are for completely rural stations. In contrast, the U.S. network is a relatively rural dataset, and less than 10% of the stations are highly urbanized. However, urbanization bias is still a significant problem, which seems to have introduced an artificial warming trend into current estimates of U.S. temperature trends. The homogenization adjustments developed by the National Climatic Data Center to reduce the extent of non-climatic biases in the networks were found to be inadequate, inappropriate and problematic for urbanization bias. As a result, the current estimates of the amount of “global warming” since the Industrial Revolution have probably been overestimated.

本数据集为以下论文的配套补充信息数据集：R. Connolly与M. Connolly（2014）《城市化偏差III：估算历史气候学网络数据集的偏差程度》，刊载于Open Peer Rev. J. 34卷（气候科学专刊），版本0.1（未同行评审草稿）。

本研究探讨了两套广泛应用的月度气温数据集受城市化偏差影响的程度。这两套数据集分别为全球历史气候学网络（Global Historical Climatology Network, GHCN）与美国历史气候学网络（United States Historical Climatology Network, USHCN），二者目前是构建各类基于气象站的全球气温趋势估算的核心数据源。
尽管全球气象网络名义上涵盖大量乡村气象站的气温记录，但其中多数记录时长偏短，或存在大规模数据缺失时段。在近100年中至少有95年保有完整数据的记录中，仅8条来自完全未受城市化影响的乡村站。与之形成鲜明对比的是，美国气象网络属于相对偏乡村的数据集，仅有不到10%的站点属于高度城市化站点。但城市化偏差仍是一个不容忽视的显著问题，其似乎为当前美国气温趋势估算引入了人为增暖趋势。
美国国家气候数据中心（National Climatic Data Center）为削减数据集内非气候性偏差所开发的均一化校正方案，经检验无法有效适配城市化偏差的校正需求，存在适用性不足、操作失当等缺陷。据此，当前对工业革命以来“全球变暖”幅度的估算，大概率存在高估情况。