The Impact of Urbanization on Global Surface Temperature Trends
Abstract
Rapid urbanization over the past half century has contributed to a warming bias in some Global Historical Climatological Network (GHCN) temperature records. The extent to which this urban warming bias contributes to global temperature trends remains largely unquantified both in raw and homogenized datasets, and no clear consensus exists on the need for specific urbanization corrections in global temperature reconstructions. In order to determine the magnitude of urbanization bias in the dataset, and to quantify the extent to which the newly adopted GHCN homogenization procedures correct for it, we examine minimum, maximum, and mean temperature trends from stations classified using numerous proxies for urbanity including MODIS, urban boundaries (GRUMP), satellite nightlights, and impermeable surface area, each created from publicly available high-resolution GIS datasets. These urbanity proxies are used to segment stations into separate urban and rural sets, and temperature differences between the two are calculated using both spatial gridding and station pairing approaches. The analysis is performed on raw and homogenized monthly data derived from the Global Historical Climatology Network (GHCN) Daily dataset that includes approximately 24,000 temperature measurement stations during the period from 1960 to present. Homogenized data that have been further adjusted using NASA GISS's Satellite Nightlight urban correction are also evaluated. The magnitude of the urbanization bias in the raw data and the degree to which this bias is mitigated with homogenization is discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMGC33B1065H
- Keywords:
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- 1632 GLOBAL CHANGE / Land cover change;
- 1640 GLOBAL CHANGE / Remote sensing;
- 1694 GLOBAL CHANGE / Instruments and techniques;
- 1946 INFORMATICS / Metadata