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The Urban CO2 Dome of Rome
Gratani, L. and Varone, L.  2005.  Daily and seasonal variation of CO2 in the city of Rome in relationship with the traffic volume.  Atmospheric Environment 39: 2619-2624.

What was done
The authors monitored atmospheric CO2 concentrations at various locations within the city of Rome in 1995, 1998 and 2001-2004.

What was learned
The data revealed the existence of a strong but variable urban CO2 dome.  Characteristics of the dome included significant temporal influences (seasonal, weekly, and diurnal), where higher values were reported in the winter months (15% greater than summer months), on weekdays (22% greater than weekends), and in the morning hours (23% greater than afternoon hours).  Spatially, CO2 concentrations at the periphery of the city averaged 405 34 and 377 16 ppm on weekdays and weekends, respectively, whereas at the city center they averaged 505 28 ppm and 414 19 ppm on weekdays and weekends, respectively.  In addition, Gratani and Varone report a strong correlation (r = 0.37, p<0.05) between traffic density and CO2 concentration; and they note that CO2 concentrations were highest during times of maximum traffic density.  Lastly, the researchers note that over the 9-year period (1995 to 2004) there was a 30% increase in the city's CO2 concentration, the reasons for which they do not directly address.  However, they state that Rome has become increasingly urbanized over the past few years, adding many new suburbs and rapidly changing into a mega-city of nearly three million inhabitants.

What it means
The results of this study suggest that the urban CO2 dome of Rome is much like that of Phoenix, Arizona and some of the Other Cities of the world where this phenomenon has been investigated.  Whether the 30% increase in its strength over the past nine years is unique or typical, however, cannot be presently ascertained, as no other urban CO2 dome studies have been conducted over as long a time span.

Reviewed 3 August 2005