The federal government needs to hire more than 270,000 workers for “mission-critical” jobs over the next three years, a surge prompted in part by the large number of baby-boomer federal workers reaching retirement age, according to the results of a government-wide survey being released Thursday.

The numbers also reflect the Obama administration’s intent to take on several enormous challenges, including the repair of the financial sector, fighting two wars, and addressing climate change…

Mission-critical jobs are those positions identified by the agencies as being essential for carrying out their services. The study estimates that the federal government will need to hire nearly 600,000 people for all positions over President Obama’s four years — increasing the current workforce by nearly one-third…

Despite the projected growth in federal jobs, the size of the government would be no larger than at most other times in the country’s post-World War II history, both in relative and absolute terms.