Review and Critical Analysis of International UHI Studies

use. In a two week intense study of the “CO2 dome” its existence was confirmed and identified as
being 75% stronger than the surrounding rural area [162].
Other papers discussing CO2 emissions concluded that:
In Kuwait atmospheric CO2 concentrations were highest in February and lowest in September.
Higher on weekdays than weekends. Higher after sun set, when conditions were more stable and
lower in late afternoon, several hours after unstable conditions [167].
A paper from the UK measured CO2 and SO2 concentrations along a transect between a city and
rural area. They found that in winter CO2 and SO2 increased towards the city at day and
nighttime. CO2 was lower in the afternoon, but SO2 was higher. In summer concentrations
increased for both but larger increases were observed on rural sites. There were uniform
concentrations over rural areas and small differences between rural and urban areas [163].
In a residential study of CO2 concentrations in Phoenix, Arizona, [165] daily maximum
concentrations occurred at nighttime but varied according to season and the air temperature.
They peaked on winter evenings and just before sunrise in the summer. Daily minimum
concentrations occurred during the afternoon. The urban mean cold season max was 67.4%
higher than the rural areas surrounding and 32.6% for the residential mean cold season
maximum. CO2 was also recorded as being in higher concentration on weekdays. Variables were
identified as air temperature inversions and solar induced convection which dilutes the pollutant
levels.
Another study on CO2 concentrations found that urban areas had 16% higher concentrations
compared to rural, the study was undertaken over a number of years, and concentrations had
actually dropped in the more recent years compared to rural areas. Again, concentrations were
highest in the early morning and lowest in the early afternoon [158].
A study looking at emissions in cities across the US found that CO2 emissions were higher in
suburban areas and during the month of July [159]. In a study in Mexico City, CO2 fluxes were at
their highest during the morning and lowest at night and fluxes correlated with traffic flow [164].
A study looking at the sources of CO2 emissions found that 80% were humans and vehicles
compared to natural sources like soil CO2 efflux (the release of CO2 from the soil) [166].
2.2.6 Health Impacts
Health conditions such as respiratory illness, heat cramps, exhaustion, non‐fatal heat stroke and
heat related mortality are all associated with urban heat islands and elevated levels of heat
compared to rural areas. Phenomenon such as heat waves put vulnerable groups such as young
children, adults with health conditions and the elderly more at risk from heat related illness.
Homes particularly at risk are those with dark roofs, on upper floors with windows on two sides
and of brick construction may experience extreme heat during heat waves [078].
Many infectious diseases are linked to changes in climate and land use. Sensitive diseases are
transmitted either indirectly or are vector‐borne diseases meaning they require a host, generally
an insect or rodent. Animals, disease carrying or otherwise, are hugely affected by changes in
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