To meet global limits on atmospheric warming, the world's governments might have to extract greenhouse gases from the air, says a new United Nations environmental report due out in the spring.

A 29-page policy summary, part of an international shift to clean energy and seen in advance by Reuters, indicates emissions around the world will have to plunge by 40 to 70 percent between 2010 and 2050 in order to meet U.N. warming targets.

The report, expected to be published in Germany in April after being edited by the Intergovernmental Panel on Climate Change, says the world community isn't doing nearly enough to achieve goals agreed to in 2010, restrict warming to about 3.6 degrees Fahrenheit above pre-industrial times, a Reuters story said.

The temperature ceiling is understood as a threshold for floods, heat waves, droughts and rising sea levels.

That said, new technologies need to be developed to remove carbon dioxide from the air.

To limit warming at all, the report states, world governments would need to invest an extra $147 billion a year in low-carbon energies like wind, solar or nuclear power from now through 2029.

Meanwhile, investments in fossil fuels would need to drop by $30 billion annually. Then, several hundred billion dollars would have to be spent yearly on making major sectors including transportation, building and industry more energy efficient.

Right now, the report said, annual investments in energy systems globally are an estimated $1.2 trillion.

"Global greenhouse gases have risen more rapidly between 2000 and 2010," the draft said, with greater reliance on coal than in previous decades.

The IPCC cautioned that the findings in the draft, dated Dec. 17, were subject to change. "This is a work in progress which will be discussed and revised in April," said Jonathan Lynn, an IPCC spokesman in Geneva.

The report estimates the costs of combating global warming overall would reduce global consumption of goods and services between 1-4 percent in 2030, 2-6 percent in 2050 and 2-12 percent in 2100, compared to no action.

China, the United States and the European Union are the top greenhouse gas emitters.