Grey hair could be a sign of a green lifestyle.
Recent research found that the average American's contribution to climate change drops after age 65.
As they near retirement, Americans pump out more per capita carbon dioxide emissions than at any time in their life, approximately 14.9 metric tons per year, according to the study published in the journal Demographics. But after 65, average emissions drop until reaching 13.1 metric tons for 80-year-olds, the greatest age for which data was available.
These results could alter projections of future greenhouse gas emissions.
"Emissions will continue to grow because the population size will continue to increase. However, they will grow less than we would have expected based only on projections of population size only," the study's author Emilio Zagheni of the Max Planck Institute for Demographic Research told Discovery News.
Zagheri correlated age to greenhouse gas production by looking at how the use of nine factors, such as air travel, gasoline and electricity, changed as people aged.
He found that gasoline use went down as people became more sedentary in later life, but home electricity and natural gas use increased.
For American seniors reducing home energy costs looks like the green choice. It could also save them some green.
"Our research confirms that utilities' costs make up a larger share of expenses for older consumers than for younger, and we work on several fronts to help ensure our members and all older Americans can better afford their home energy bills," Tiffany Lundquist, media relations manager for the AARP, formerly known as the American Association of Retired Persons, told Discovery News.
Some older Americans take action to reduce bills and pollution.
"In our publications, web site, and educational outreach, environmental features are popular and we frequently highlight tips on saving money on home energy costs," said Lundquist.
"Our members' interest in this work is demonstrated in part by their active volunteerism in support of it. As an example, the 'Operation Energy Save' toolkit, which people can use to help friends and neighbors conserve energy, is among the more popular of the offerings on our volunteerism web site, Create the Good," Lundquist said.
Energy saving seniors may be able to reduce their carbon footprint, but it won't solve the climate change problem.
Census results show the average age of the populations of the United States, Europe and Japan is increasing. But this demographic shift won't result in emissions reductions until this century is half over.
The study suggests that until 2050, aging may actually account for a slight increase in emissions, since people's greenhouse gas contribution continues to increase until around age 65.
"In the longer term, as more and more people will be older than 65, emissions are expected to decrease. This is partially related to the fact that people at older ages produce less emissions and that a reduction of the proportion of people in the labor force tends to slow the growth in the size of the economy, and thus consumption and emissions," Zagheri explained to Discovery News.
Although the developed world now has a touch of gray, many emerging economies have a youth bulge.
"Aging is expected to have the same beneficial effect in developing countries in the long term. However, it is very likely that the increase in affluence and the process of urbanization and development will more than counteract the beneficial effect of aging on carbon emissions," Zagheri said.
© 2012 Discovery Channel