Greenhouse Gas Emissions In Cities Research Articles

Vulnerability of Mexico City's water supply sources in the context of climate change

In the context of growing urbanization and climate change, the issue of how to best secure and increase future water supply in developing countries is key. To support informed decision-making in Mexico City, a comprehensive study was conducted to assess the potential effects of climate change and the vulnerability of water sources. The infrastructural, environmental and administrative factors affecting the water available from each source were identified and evaluated, and then combined with the likely impacts in regional water availability estimated using results from two global circulation models and two emission scenarios. The results obtained indicate that the water sources outside Mexico City, such as the Cutzamala and Lerma systems, are the most vulnerable. The current situation is likely to become worse as a result of climate change, as projections suggest a 10–17% reduction in water availability by 2050. When responsible agencies decide the strategies to secure and increase water supply, they will have to consider the prevailing and potential conflicts, the local water demand, the contribution to the city's greenhouse gas emissions and future changes in water availability.

Contribution of Water and Wastewater Infrastructures to Urban Energy Metabolism and Greenhouse Gas Emissions in Cities in India

This is a first analysis of end-use energy intensity (EUEI) and greenhouse gas (GHG) emissions in water and wastewater (W/WW) sectors in India, and it examines their contribution to community-wide energy use and GHG emissions in cities in India. EUEI and related GHG emissions for W/WW infrastructures in Indian cities were analyzed and compared with data for cities in the United States. Data gathered by ICLEI-South Asia, Government of India, and the University of Colorado Denver were used to conduct this analysis. W/WW infrastructures were found to contribute 3-16% of community-wide electricity use and GHG emissions for 16 cities in India; for another 23 cities, the proportion was less than 3%. EUEI for drinking water supply and wastewater treatment averaged 0.3 � 0.2 W· h=Lðn ¼ 7Þ and 0.1 � 0.05 W·h =Lðn ¼ 5Þ, respectively. EUEI for drinking water provision was more than double that for wastewater treatment, the reverse of typical cities in Colorado, likely a result of poorer source water quality in India. In general, although the sample size of Indian W/WW plants is small, EUEI in India appears to be much smaller than in the United States for both water and wastewater sectors based on this first review of quantitative data. DOI: 10.1061/(ASCE)EE.1943-7870.0000661. © 2013 American Society of Civil Engineers. CE Database subject headings: Wastewater management; Urban areas; Emissions; India; Water management. Author keywords: Urban metabolism; End-use energy intensity; Greenhouse gas; Water infrastructure; Wastewater; Developing cities.

Correction to “Carbon sequestration and greenhouse gas emissions in urban turf”

[1] In the paper “Carbon sequestration and greenhouse gas emissions in urban turf” by A. Townsend-Small and C.I. Czimczik (Geophysical Research Letters, 37, L02707, doi:10.1029/2009GL041675, 2010), we discovered an error in the calculation of carbon dioxide (CO2) emissions from fuel consumption during turfgrass maintenance. The data for fuel consumption and park area described in the original publication are correct. Park management contractors use about 2700 gallons of gasoline per month to maintain a total park area of about 2 × 106 m2 [Townsend-Small and Czimczik, 2010]. We assumed that one gallon of gasoline equaled 2421 g C [Environmental Protection Agency, 2005] and a combustion efficiency of 85% [Lal, 2004]. This results in CO2 emissions from fuel usage of 122 g CO2 m−2 yr−1, not 1469 g CO2 m−2 yr−1 as originally reported [Townsend-Small and Czimczik, 2010], or about 24% of the organic carbon (OC) storage per m−2 shown in ornamental lawns (Figure 3 of the current study). [2] This changes the total global warming potential (GWP) of both ornamental lawns and athletic fields (Figure 3b). Based on this correction, the total GWP of ornamental lawns ranges from −108 g CO2 m−2 yr−1 for the low fertilization scenario (10 g N m−2 yr−1) to +285 g CO2 m−2 yr−1 for the high fertilizer scenario (75 g N m−2 yr−1). In athletic fields, which do not store OC in soils, there is a positive GWP ranging from +405 to +798 g CO2 m−2 yr−1 for the low and high fertilizer scenarios, respectively. Our estimates of global warming potential also have errors associated with our measurements of carbon sequestration and N2O production (error bars in Figure 3). Ornamental lawn OC sequestration ranges from −513 +37 to −513 −73 g CO2 m−2 yr−1, with uncertainties estimated from calculating OC sequestration rates based on the standard error (SE) of OC stocks at each time point. N2O emissions range from 45 +108 to 45 −25 g CO2 m−2 yr−1 at a fertilization rate of 10 g N m−2 yr−1 and from 145 + 109 to 145 − 73 g CO2 m−2 yr−1 at a fertilization rate of 75 g N m−2 yr−1. Uncertainties in N2O emissions were calculated from the SE of flux during fertilizer pulses and the 25% or 75% interquartile of the baseline flux. [3] This reanalysis shows that there may be a potential for urban ornamental lawns to sequester atmospheric CO2 if they are managed conservatively (Figure 3b). However, intensive management practices such as frequent application of inorganic fertilizers, irrigation, and fuel consumption from mowing and leaf blowing all decrease the likelihood that urban turfgrass can mitigate greenhouse gas emissions in cities.

Are we missing the point?

The discourse on how to reduce greenhouse gas emissions in cities is dominated by ecological modernization theory, which focuses primarily on technological approaches supported by market mechanisms to curb carbon emissions. This discourse has contributed to a research and management agenda. Yet this is based primarily on perceptions and precedents drawn from high-income nations. This paper draws on empirical evidence from Latin American cities for a critical discussion of the usefulness and limitations of this approach when applied to cities in low- and middle-income nations. The paper suggests that for such cities, ecological modernization is an inappropriate framework for addressing global (and local) environmental problems.