Slower population growth may help reduce global emissions:
18, 2010 - Xinhua
Slower population growth could contribute to significantly reducing greenhouse
gas emissions, a new study suggests.
"If global population growth slows down, it is not going to solve the
climate problem, but it can make a contribution, especially in the long term," said
the study's lead author, Brian O'Neill, a scientist at the National Center
for Atmospheric Research (NCAR).
Such slow growth paths by 2050 could account for 16 to 29 percent of the emissions
reductions thought necessary to keep global temperatures from causing serious
impacts, according to the study conducted by an international team of scientists
from the NCAR, the International Institute for Applied Systems Analysis ( IIASA),
and the National Oceanographic and Atmospheric Administration.
The effect of slower population growth on greenhouse gas emissions would be
even larger by the end of the century, said the study appearing Monday in Proceedings
of the National Academy of Sciences.
Slower population growth will have different influences, depending on where
it occurs, said study co-author, IIASA scientist Shonali Pachauri.
"A slowing of population growth in developing countries today will have
a large impact on future global population size. However, slower population
growth in developed countries will matter to emissions, too, because of higher
per capita energy use," Pachauri said.
Scientists have long known that changes in population will have some effect
on greenhouse gas emissions, but there has been debate on how large that effect
In the latest study, the researchers sought to quantify how demographic changes
influence emissions over time, and in which regions of the world. They also
went beyond changes in population size to examine the links between aging,
urbanization, and emissions.
The team found that growth in urban populations could lead to as much as a
25 percent rise in projected carbon dioxide emissions in some developing countries.
The increased economic growth associated with city dwellers was directly correlated
with increased emissions, largely due to the higher productivity and consumption
preferences of an urban labor force, the researchers said.
In contrast, aging can reduce emissions levels by up to 20 percent in some
industrialized countries, mainly because older populations are associated with
lower labor force participation, and the resulting lower productivity leads
to lower economic growth, according to the study.
"Demography will matter to greenhouse gas emissions over the next 40
years," said O'Neill. "Urbanization will be particularly important
in many developing countries, especially China and India, and aging will be
important in industrialized countries."
"Households can affect emissions either directly, through their consumption
patterns, or indirectly, through their effects on economic growth," O'Neill
By mid-century it is estimated that global population could rise by more than
three billion people, with most of that increase occurring in urban areas,
according to the study.
The researchers developed a set of economic growth, energy use, and emissions
scenarios, using a new computer model (the Population- Environment-Technology
model, or PET). To capture the effects of future demographic change, they distinguished
between household types, looking at age, size, and urban vs. rural location.
In addition, they drew on data from national surveys covering 34 countries
and representative of 61 percent of the global population to estimate key economic
characteristics of household types over time, including labor supply and demand
for consumer goods.
The study also suggests that developers of future emissions scenarios give
greater consideration to the implications of urbanization and aging, particularly
in the United States, the European Union, China, and India.
"Further analysis of these trends would improve our understanding of
the potential range of future energy demand and emissions," said O'Neill.
The researchers caution that their findings do not imply that policies affecting
aging or urbanization should be implemented as a response to climate change,
but rather that better understanding of these trends would help anticipate