Could better monitoring of cities' emissions encourage the US to join climate treaties?
- 09 Oct 2012, 17:30
- Roz Pidcock
A study published today outlines a new way to map the emissions
produced by cities. Cities are major contributors to global climate
change, so the authors say this could be an important step forward
in meeting emission reduction targets.
Cities - as hubs of industry, housing, business and transport -
are responsible for more than 80
per cent of greenhouse gas emissions worldwide, according to
the World Bank. With the
global population approaching nine billion and 68 per cent of people expected
to be living in urbanised areas by 2050, the way cities develop in
the future is set to be critical when it comes to setting and
meeting international emission reduction targets.
While all countries under the United Nations Framework
Convention on Climate Change (UNFCCC) are legally obliged to report
their national greenhouse gas emissions, different countries use different
methods to do so. This inconsistency filters through to the
city level. Although a large chunk of the responsibility to reduce
national emissions will fall to cities, an international standard
for working out how much cities contribute also isn't settled.
A
new study published today in the journal Environmental Science
and Technology lays out a new method for quantifying greenhouse gas
emissions for individual buildings every hour for an entire city.
Professor Kevin Gurney from the Global Institute of Sustainability
at Arizona State University and lead author of the study explains
why this is important:
"Cities
have had little information with which to guide reductions in
greenhouse gas emissions - and you can't reduce what you can't
measure".
Tracking
emissions
Previous research has tended to estimate cities' emissions on a
much broader level, based on data on industrial energy use and
average domestic consumption. The new research takes advantage of
the growing number of atmospheric measurements made at city level
to dig deeper into exactly where the emissions come from.
A still from a video of
hour-by-hour changes in carbon dioxide emissions from different
building types for the US city of Indianapolis. Credit: Bedrich
Benes and Michel Abdul-Massih
The team of scientists collected a range of 'bottom up' data
about carbon dioxide emissions from air pollution reports, traffic
surveys and basic information about building type and size
collected for tax purposes. They combined these data with a
computer modelling system which calculated energy consumption on a
building-by-building basis.
As Gurney explains, users can track the emission intensity for
the whole city using colour-coded, high resolution maps and use
them to make decisions on where efforts to reduce emissions would
be most effective. He says:
"...[T]he
emission mitigation impact of targeting older, less insulated homes
can be quantified and compared to targeting zones of congested,
high-emitting on-road sources".
Decision-making
tool
As well as providing information in a way that is useful to
local decision-makers, the colourful visual displays of daily or
seasonal variations in emissions from different sources -
residential buildings, industry and transport - also make it easier
for ordinary people to see the impact they can make locally to help
mitigate climate change. Gurney adds:
"...[W]e
can provide cities with a complete, three-dimensional picture of
where, when and how carbon dioxide emissions are occurring...to
identify the most cost-effective ways to reduce emissions and track
progress over time".
The issue of scale is important in emissions accounting for
cities. Previous
research for the city of Toronto has shown that the differences
in emissions intensity within the city can be as big as the
difference between cities. For example, residents of high-density
apartment blocks in dense city centres can emit half as much carbon
dioxide as neighbouring residents in single family homes in the
suburbs.
So far the researchers have used the new method in one city in
the United States, Indianapolis, but they say it can be reproduced
across all major US cities, which together are responsible for
nearly 25 per cent of all global carbon dioxide emissions. The
researchers are already working on estimates for Los Angeles,
California and Phoenix.
What about international
treaties?
On an international scale, the team suggests this new tool may
help encourage the US to sign up to international climate change
treaties. In the past, comparing different countries' stated
emissions without having a way to independently verify them has
cast doubt over how to incorporate them into mitigation
agreements to follow on from the Kyoto
Protocol.
The study is part of a larger project called 'Hestia',
named after the Greek goddess of the hearth and home, which
combines ground-based and satellite measurements of methane and
carbon monoxide as well as carbon dioxide. The results from Hestia
are expected to complement the launch of the Orbital Carbon Observatory
satellite, planned for December 2013, which will measure the
concentration of carbon dioxide in the atmosphere.
One thing to note is that the new method does not account for
material or electricity consumed within the city but produced
elsewhere. A study led by the World Bank in 2011 shows that the
greenhouse gas emissions for the same urban resident can vary
significantly depending on whether production or consumption,
or both, are taken into account when calculating greenhouse gas
emissions.
All this shows that clarity counts when calculating urban
emissions if countries are to adopt an international standard. But
this research by US scientists could make a valuable contribution
to creating a standard that countries can agree on.
The full video for the Hestia
projects and shorter videos of emission calculations over time for
Indianapolis can be found on the project website here.