Elevated atmospheric CO2 concentration and temperature across an urban–rural transect

Abstract

The heat island effect and the high use of fossil fuels in large city centers are well documented, but by how much fossil fuel consumption is elevating atmospheric CO 2 concentrations and whether elevations in both atmospheric CO 2 and air temperature from rural to urban areas are consistently different from year to year are less well known. Our aim was to record atmospheric CO 2 concentrations, air temperature and other environmental variables in an urban area and compare it to suburban and rural sites to see if urban sites are experiencing climates expected globally in the future with climate change. A transect was established from Baltimore city center (Urban site), to the outer suburbs of Baltimore (suburban site) and out to an organic farm (rural site). At each site a weather station was set-up to monitor environmental variables for 5 years. Atmospheric CO 2 was consistently and significantly increased on average by 66 ppm from the rural to the urban site over the 5 years of the study. Air temperature was also consistently and significantly higher at the urban site (14.8 1C) compared to the suburban (13.6 1C) and rural (12.7 1C) sites. Relative humidity was not different between sites whereas the vapor pressure deficit (VPD) was significantly higher at the urban site compared to the suburban and rural sites. An increase in nitrogen deposition at the rural site of 0.6% and 1.0% compared to the suburban and urban sites was small enough not to affect soil nitrogen content. Dense urban areas with large populations and high vehicular traffic have significantly different microclimates compared to outlying suburban and rural areas. The increases in atmospheric CO 2 and air temperature are similar to changes predicted in the short term with global climate change, therefore providing an environment suitable for studying future effects of climate change on terrestrial ecosystems.

Variations in Atmospheric CO2 Mixing Ratios across a Boston, MA Urban to Rural Gradient

“…When integrated across the day, Vulcan mobile source emission estimates were 42.7% and 58.7% higher during the weekday compared to weekends in Boston and Worcester, respectively, which is consistent with elevated CO 2 mixing ratios observed during weekdays at each site. Observational studies in Portland and Phoenix showed weekday/weekend differences as high as 4.0 and 14.4 ppm, respectively [15,41], while a study from suburban Baltimore showed no significant weekend difference [17]. Weekend effects reflect the importance of local commuting patterns on observations of CO 2 mixing ratios.…”

“…For example, CO 2 mixing ratios have been found to be higher in urban centers compared to adjacent rural locations in Phoenix [15], Salt Lake City [16], and Baltimore [17]-a phenomenon known as an "urban CO 2 dome". These higher mixing ratios are due in part to local traffic emissions, as seen in Helsinki [18], Mexico City [19], and Basel [20], but may also be effected by residential, commercial, and industrial emissions.…”

A Mobile Measuring Methodology to Determine Near Surface Carbon Dioxide within Urban Areas

“…Measuring the gradient of carbon dioxide between urban and rural locations (e. g. Berry & Colls, 1990a/b;Ziska et al, 2004;George et al, 2007). All of these studies were carried out by stationary measurements.…”

Evolution and variation of atmospheric carbon dioxide concentration over terrestrial ecosystems as derived from eddy covariance measurements

“…The consistent long-term increase in atmospheric CO 2 concentration makes it important to explore the temporal variations of atmospheric CO 2 . Meanwhile, it is also important to examine the spatial variations since atmospheric CO 2 concentration in the surface layer of the atmosphere varies significantly over different land covers (George et al, 2007;Zhang et al, 2008;Jacobson, 2010), although CO 2 is generally assumed to be wellmixed in the boundary layer. Better knowledge of the temporal and spatial variations of CO 2 concentration in the surface layer of the atmosphere is needed to improve the forecast of future CO 2 concentration levels (Wu et al, 2012).…”