Efforts to respond to the varied and complex consequences of
human-influenced climate change may be locked in long-term political quagmire.
At the local level, though, the equation is simpler: It's a matter of life and
In Indiana's capital city, human activities such as
deforestation and development — the very endeavors that created the city,
really — fashioned a hot spot right in the center of the state. In
effect, they've changed the climate. And, along with this increased temperature
pressure, the city must cope with higher densities of vulnerable populations,
most notably people without air conditioning.
Though tornadoes may be the top cause of weather-related
deaths this year, extreme heat events are typically the no. 1 cause in North
America, according to Daniel Johnson, an assistant professor of geography at
IUPUI, the Center for Urban Health and Center for Health Geographics.
Each year, Indianapolis experiences an average of three
deaths directly attributed to heat, but experts say this number is
underreported because deaths attributed to cardiovascular or respiratory
conditions may have been inflamed to fatal levels by high temperatures.
The pressures are at times much more marked, though, and
widespread death occurs, Johnson told an audience gathered at the 2011 Indiana
Environmental Health Summit earlier this summer. Examples he offered included
an estimated 600 heat-related deaths in Chicago in the summer of 1995 and 181
deaths in Philadelphia in 1993. Also, heat, coupled with the effects of
heat-related wild fires, was linked to 56,000 deaths in Russia last year, he
More deaths are noted in areas with higher surface temperature,
In Indianapolis, Johnson works with emergency management and
the Indianapolis Health Department to use mapping tools to locate areas of
special concern. Researchers layer various types of information to develop
strategies to combat heat-related emergencies.
"This is a good slide to show to anthropogenic climate
change skeptics," Johnson said at the environmental summit, displaying a
map of land surface temperature in Indiana that reflects dramatic differences
between urban and rural surface temperatures as captured by NASA's MODIS, or
Moderate Resolution Imaging Spectroradiometer, satellite. [See image.]
"Through changes we've made to our environment, we've
changed the urban climate in these locations — this more or less can't be
Average temperatures taken across the region may not reflect
the magnified intensity experienced in what experts call urban heat islands.
The regional forecast may, for instance, peg Indianapolis at 95, Shelbyville at
93, Terre Haute at 95 and Columbus at 92.
Likewise, intensity of summer heat does not average a
certain number of degrees hotter with each new acre of asphalt sprawling beyond
the urban core. Data compiled by the Indiana State Climate office underscore
the ongoing variability of average temperature trends.
When the heat index hits 105 or higher, the National Weather
Service typically issues heat advisories or warnings.
In the past two decades, the number of days crossing into
this threshold of extreme heat range from a high of eight in 1990 to none in
2008. Last year, five days crossed over to that level. So far this year, at
least two days have already hit that mark.
Indiana State Climatologist Dev Niyogi explained urban heat
island effects are well documented and "highly localized" phenomena
measured and experienced at a micro level.
By honing the MODIS data into a tighter scale, Johnson's
mapping exercises reveal how these variations are expressed across different
areas of the city.
The maps reveal what Johnson called "dramatic
changes" in the distribution of urban heat islands in the past three
decades and their relationship to vulnerable populations across the city
between 1990 and 2000.
Johnson's team is waiting for the U.S. Census Bureau to
release detailed elements of the recent decennial census, which will enable
researchers to understand recent population shifts and better assess the city's
current state of vulnerability.
Their definition of vulnerability includes socio-economic
factors that influence a person's potential to access air conditioning in
addition to features of the natural landscape such as percent of tree cover.
"We have seen the heat island become more dispersed
which is not necessarily a good thing because with urban sprawl services are
more thinly spread and the effects of mitigation strategies are diluted,"
Johnson told NUVO.
"Additionally, we have seen some changes in the social
vulnerability and its spatial distribution. This, in coincidence with the
dispersed urban health effects, can lead to different levels of vulnerability
Mapping vulnerability helps local health officials better
implement heat-mitigation strategies, such as where they might introduce
cooling centers and employ educational campaigns about the health hazards
associated with extreme heat.
"High social risk areas usually have low tree
cover," Johnson said.
Urban heat islands, which can run more than five degrees
hotter than surrounding rural regions during the day, retain their heat when
the sun goes down.
In the evening, the difference can run as high as 22
degrees, according to the U.S. Environmental Protection Agency.
Though urban heat islands are experienced on a micro-scale,
with dramatic variations across a city's different neighborhoods, the
implications of urban climate change present issues of much broader interest.
In addition to his position as state climatologist, Dev
Niyogi is also an associate professor at Purdue University, specializing in
land use, land cover change and its affect on weather and climate.
His recent research concerns the effects of urban landscapes
on thunderstorm distribution. A study published by the Journal of Applied
Meteorology and Climatology, in which Niyogi was lead author, found "that
more than 60 percent of storms changed structure over the Indianapolis area as
compared with only 25 percent over the rural regions."
This finding relates to earlier findings that "the
distribution of urban area and anthropogenic heating could greatly influence the
distribution and amount of regional rainfall" ultimately affecting the
variability of precipitation around urban areas. Some studies have suggested
that urban splitting of storm systems may reduce precipitation in large cities
and increase storm intensity downwind.
Climate, Niyogi told NUVO, is like politics in that it is
local and heavily influenced by the features in your backyard. Local
environment influences everything from residents' general comfort to air
quality, heating and cooling expenses and the severity of drought, he said.
Currently, Niyogi said, researchers are engaged in
identifying risk assessment tools to help people devise the most effective
decision-making tools in response to behavior of the local climate. Other
topics of research exploring climate-change mitigation strategies include
studies of urban tree cover, reforestation strategies and green roofing design.
Macro weather pressures such as thunderstorms are still
natural and uncontrolled phenomena. Niyogi likens them to a hammer, while
climate changes linked to human influence are more like a chisel: "While
we can't control the hammer, the placement of the chisel is in our hands, at
times, through local planning."