Findings published by Australia's Commonwealth Scientific and Industrial Research Organization also showed that 2005 marked the fourth-consecutive year of increased carbon dioxide emissions.
"To have four years in a row of above-average carbon dioxide growth is unprecedented," Paul Fraser, a scientist with the CSIRO's center for marine and atmospheric research, said in a statement.
The study analyzed a 30-year record of air samples collected at an Australian Bureau of Meteorology observation station on the southern island state of Tasmania.
Mike Raupach, a scientist with the organization, said from 2000 to 2005 the growth rate of carbon dioxide emissions was more than 2.5 percent per year, whereas in the 1990s it was less than 1 percent per year.
The World Meteorological Organization reported a few weeks ago that carbon dioxide levels in the atmosphere are now 35% higher than in the late 18th century.