Deborah Zabarenko PlanetArk 12 Oct 10;
The world is probably going to be a more crowded place by 2100 and demographic changes in this growing population -- how many more people there are, how old they are and where they live -- will affect climate-warming emissions, researchers reported on Monday.
Slowing down population growth could have a profound effect on the level of carbon dioxide emissions from fossil fuel use, the researchers found, but this alone will not be enough to prevent the most severe impact from climate change.
Scientists have long drawn a connection between population growth and increased greenhouse gas emissions, but previous research has not focused on demographic shifts that are likely to go along with the increase in the number of people.
World population is expected to be generally older and more urban by century's end, and more people are likely to live in smaller households rather than in extended families, U.S., German and Austrian researchers reported in the Proceedings of the National Academy of Sciences.
But how many people might there be? The researchers considered three scenarios: a continuation of current trends, which would yield a 2-billion-person increase by 2050; a slower growth path which could mean about 1 billion more people; and a faster growth path, which could see a population rise of as much as 3 billion by 2050.
That would mean about 9 billion people living on Earth, compared to more than 6 billion now.
A slower-growth path could cut emissions by 16 to 29 percent of the amount needed to keep global temperatures from causing serious effects, the researchers said. And an aging population with lower participation in the workforce could cut emissions by as much as 20 percent in some industrialized countries.
POSSIBLE RISE IN ASIAN ENERGY DEMAND
Generally speaking, the more people there are, the more fossil fuel they use, causing more greenhouse gas emissions. But those who live in rural areas, particularly in developing countries, use more biomass as fuel instead of fossil fuels like coal and oil, said Brian O'Neill of the U.S. National Center for Atmospheric Research, one of the study's authors.
Therefore, a big move from country to city living is likely to mean greater fossil fuel use, especially in the developing world. Even if city-dwellers have relatively smaller carbon footprints -- living in smaller spaces, using public transit and less fossil fuel per person -- an influx of country people into cities is likely to make greenhouse emissions rise.
Another effect of urbanization is that urban workers tend to contribute more to economic growth than rural workers do.
"That's not because they work harder or longer hours," O'Neill said by telephone from Boulder, Colorado.
"It's because they're in sectors of the economy that drive economic growth more."
As a result, he said, the whole economy of the country grows faster and overall demand for energy rises, driving emissions up, as much as 25 percent in some developing countries.
The trend toward urbanization could have a noticeable impact on energy demand, especially in Asia, O'Neill said.
"I think it's possible ... that we're underestimating potential growth rates in energy demand in regions of the world that may urbanize very quickly over the next 20 to 30 years," he said.
(Editing by Todd Eastham)
Urbanization, Aging Will Affect Greenhouse Gas Emissions
LiveScience.com Yahoo News 13 Oct 10;
As the number of humans already on Earth has resources bursting at the seams, researchers are now finding it's not just population size that impacts the planet's health. The composition of that population and where they live also play huge roles in the release of greenhouse gases.
Aging and urbanization, in particular, could significantly affect global emissions of carbon dioxide over the next 40 years, according to new research published this week in the journal Proceedings of the National Academy of Sciences.
"By examining the relationship between population dynamics and greenhouse gas emissions, this groundbreaking research increases our understanding of how human behaviors, decisions and lifestyles will determine the path of future climate change," said Sarah Ruth, program director in the National Science Foundation (NSF), which funded the study, along with a European Young Investigator's Award, and the Hewlett Foundation.
By mid-century it is estimated that the global population could rise by more than 3 billion people, with most of that increase occurring in urban areas, the researchers say.
To figure out how these changing demographics might impact climate change, the researchers developed scenarios for energy use, emissions and economic growth using a computer model (Population- Environment-Technology model, or PET).
They also analyzed 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.
Overall, they found that if population follows one of the slower growth paths foreseen by demographers at the United Nations, by 2050 it could account for 16 to 29 percent of the emission reductions thought necessary to keep global temperatures from causing serious impacts, the researchers found.
"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 study researcher Brian O'Neill, of the National Center for Atmospheric Research (NCAR) in Boulder, Colo.
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 population.
On the other hand, aging could reduce emissions levels by up to 20 percent in some industrialized countries, a finding that also had to do with productivity - older people are less likely to participate in the labor force or have lower labor productivity, and are associated with slower economic growth, the researchers say.
"Demography will matter to greenhouse gas emissions over the next 40 years," O'Neill said. "Urbanization will be particularly important in many developing countries, especially China and India, and aging will be important in industrialized countries."
The authors suggest that developers of future emissions scenarios give greater consideration to the implications of urbanization and aging, particularly in the United States, European Union, China and India.
"Further analysis of these trends would improve our understanding of the potential range of future energy demand and emissions," O'Neill said.
The research was conducted by scientists at NCAR, the International Institute for Applied Systems Analysis (IIASA), and the National Oceanographic and Atmospheric Administration (NOAA).
