The National Oceanic and Atmospheric Administration spends roughly $6 million per year to sample carbon dioxide, methane and nearly 20 other gases using a global network of ground stations, tall towers and aircraft.

But faced with shrinking budgets and an uncertain fiscal future, NOAA has stopped measuring greenhouse gas levels at a dozen ground stations, eliminated some aircraft monitoring and cut the frequency of remaining measurements in half. The agency scrapped plans to expand its network of tall towers and is now moving to shut down some of the seven existing sites.

The cuts come at a time when governments are pushing for more detailed information about sources and sinks of greenhouse gases. Scientists say the decision to shrink NOAA's monitoring network -- the world's largest -- threatens their ability to provide those answers.

"The reality is that countries are making commitments that will cost millions, if not billions, of investment in climate-related work, and governments want more certainty about what's happening, what other countries are doing," said Pep Canadell, executive director of the Global Carbon Project. "We barely have enough to provide what a lot of agencies are asking for. The prospect of having fewer sampling stations around the world is a frightening one."

Canadell is one of more than 50 researchers who signed a letter, published last week in the journal Science, warning that additional cuts to NOAA's monitoring program could harm U.S. national security and render useless the hundreds of millions of dollars that several nations, including the United States, have spent developing new CO2-monitoring satellites.

Putting a crimp in long-term monitoring
The situation is likely to get worse before it gets better.

Last year, NOAA sought $5.5 billion but received $600 million less with Congress slashing the agency's ocean, fisheries and research accounts. Lawmakers also approved legislation that mandates automatic, across-the-board spending cuts beginning in January.

Agency sources said they have been told to expect a budget cut of at least 5 percent for fiscal 2013, which begins Oct. 1.

"What you've got is a critical and small -- in terms of dollars -- operation that is being subjected to targeted strain," said Scott Lehman, a research professor at the University of Colorado, Boulder, said of NOAA's monitoring effort. "You don't balance the federal budget on the strength of $6 million programs."

NOAA's greenhouse gas monitoring network continues work that began in 1958, when Charles Keeling, a geochemist at the Scripps Institution of Oceanography, began measuring atmospheric CO2 levels at Mauna Loa, Hawaii.

Keeling's monitoring produced the now-famous "Keeling curve," a graph showing the steady growth of atmospheric carbon dioxide levels over the last 54 years, from 315 parts per million in 1958 to roughly 392 parts per million today.

"Without that, all we are, scientifically, is totally blind about what's happening in the atmosphere," said Taro Takahashi, an ocean scientist at Columbia University's Lamont-Doherty Earth Observatory.

NOAA began making its own measurements of CO2 at Mauna Loa in 1974, an effort that eventually expanded to roughly 100 sites around the world where the agency monitors 20 gases that affect the global carbon cycle using samples collected by ground stations and observatories, tall towers and aircraft (ClimateWire, Dec. 14, 2009).

"We like long-term measurements," said Pieter Tans, who leads NOAA's greenhouse gas monitoring effort, which is based at the agency's Earth System Research Laboratory in Boulder, Colo. "We'd like at certain sites to stay there for many decades, because trends in the differences between sites tell you something about emissions, about changes in uptake or output in large regions."

Cuts could reverberate internationally
Continuous measurements of atmospheric CO2, carbon monoxide and methane form the backbone of NOAA's monitoring network. They are collected at the agency's six observatories -- in Hawaii, Alaska, Greenland, Antarctica, American Samoa and California -- and seven tall towers scattered across the United States.

NOAA supplements those measurements with air samples collected regularly in flasks on the ground and in the air, which provide information about a broader range of gases and help expand geographic coverage that helps scientists understand local variations in greenhouse gas output.

The majority of the monitoring sites are run by "volunteers" who submit samples and data to NOAA at no cost. At other sites, the agency must pay for measurements -- like air samples collected in flasks during regular flights of small, private planes at 15 U.S. sites.

Those pay-to-play sites were first on the chopping block when the recent budget cuts began. Now, with NOAA managers anticipating a 5 percent budget reduction in fiscal 2013, scientists in and out of the agency say they're worried that the greenhouse gas monitoring program will be forced to cut personnel.

Many say they're concerned that if NOAA's program continues to shrink, monitoring efforts in other countries could suffer. In addition to operating the largest global network measuring greenhouse gases and ozone-depleting substances, NOAA maintains standards that ensure other countries doing similar work are of high quality and in compatible formats.

The U.S. effort has served as a model -- and a continuing reference -- for programs in Europe, China, India and Brazil.

And with a new generation of CO2-monitoring satellites now in development, ensuring the continuation of ground-based measurements of greenhouse gases has taken on new importance, experts said.

Satellite data 'wasted' without ground monitoring
Japan's GOSAT, now in orbit, and NASA's Orbiting Carbon Observatory-2, still in development, are designed to provide regular measurements of atmospheric carbon dioxide in places ground measurements have not reached.

According to recent reports by the National Academy of Sciences and JASON, an independent group of scientists that advises the government, that kind of satellite coverage will be crucial to determine whether individual nations comply with emissions cuts outlined in future climate pacts.

But satellites cannot supplant ground-based monitoring networks, said Sander Houweling, an atmospheric scientist at Utrecht University in the Netherlands who helped organize the Science letter.

"In the foreseeable future, it is not going to be like that," Houweling said. "With measurements from satellites, we have to learn how to make sure they are on the same scale as ground-based measurements. In the current phase, we are exploring how to make use of measurements taken from space."

Canadell of the Global Carbon Project agreed. "This is not threatening the need for these atmospheric, high-precision measurements," he said. "To the contrary, it makes them even more critical. Otherwise, these hundreds of millions of dollars we spend on every single satellite get wasted."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500