By Molly Bentley
At a time when climate change impacts are accelerating, our ability to observe those impacts from space is deteriorating.
Nasa's Earth observation capacity is under threat, critics say
Cuts in US government funding for Nasa programmes will dramatically weaken scientists' capacity to monitor and understand the planet's climate; at least, so says a major study from the National Research Council (NRC), published earlier this year.
If present trends continue, they conclude, by 2015 the number of US Earth-observing satellite missions will be reduced by half, putting the scientific systems they support "at risk of collapse".
They warn that such a loss would severely hamper the ability of scientists to collect basic information about the Earth's climate system, to monitor changes - including those that directly affect human health, such as disease outbreaks and water contamination - and provide accurate weather forecasts.
Programmes involving measurements of temperature, ozone, ocean winds, water vapour, and solar radiation are among those expected to be curtailed.
The substitution of more economical but less capable instruments on some missions will worsen forecasts of El Nino, hurricanes and coastal weather, the study says.
The warnings of reduced observing capability come with the Intergovernmental Panel on Climate Change (IPCC) in the middle of a sequence of major reports which are painting a picture of likely climate change impacts around the world.
"We need to understand the planet's climate and how it's going to change," says Berrien Moore, director of the Institute for the Study of Earth, Ocean and Space at the University of New Hampshire, and co-lead author of the NRC study.
"To permit the Earth-observing capability to diminish at this time is unwise."
Due to a series of cancelled or delayed missions, ageing satellites and instruments, and decline in funding for new projects, the nation's space-based observing programme is in disarray, the study's authors believe.
A committee of more than 100 leading American scientists and policy-makers authored the NRC report.
The NRC was responding to a request by Nasa, the National Oceanic and Atmospheric Administration (Noaa) and the US Geological Survey to assess the health of the field and recommend priority space-based missions that fit with their research programmes.
Satellites have been essential to understanding Earth processes. These eyes in the sky allow scientists to take measurements which would be impossible by other means.
"Our knowledge of how the climate has changed and is changing relies heavily on satellite remote sensing," comments Richard Somerville from Scripps Institution of Oceanography at the University of California in San Diego, a lead author on the recent IPCC climate science report.
"How are you going to measure shrinking sea ice without a satellite?" he asks.
"The Arctic is a big place, and you can't have guys floating out there in canoes taking measurements."
As well as monitoring the changing climate, satellites provide basic information about the workings of the climate system and the poorly understood role of clouds, ice, and aerosol particles, he says.
The NRC Earth-observation report recommends that 17 new satellite missions be flown in the next decade. They were chosen from over 100 proposed missions based on cost, readiness, and the potential to answer critical scientific and policy questions, among other criteria.
The new satellites would be developed for launch between 2010 and 2020, with price tags for each mission ranging from $65m to $650m (£30m to £300m).
Each would provide key measurements to help form an integrated picture of the planet's dynamics. This would help researchers answer basic scientific questions about the climate system, monitor climate change, and forecast weather.
Some new projects could help monitor risks to human health. For example, one mission designed to monitor soil moisture may contribute to more reliable forecasts of vector-borne disease outbreaks.
The recommended missions could be run within the amount that Nasa spent for Earth science eight years ago, the NRC concludes.
"It's clearly affordable," says Richard Anthes from the University Corporation for Atmospheric Research, one of the report's co-lead authors.
"To do the entire programme would cost the American public $2 per person per year."
None of the recommended new missions is slated for funding under President Bush's proposed 2008 budget.
The NRC study also expresses concern about missions that have been scaled back.
High on the list is the National Polar-orbiting Operational Environmental Satellite System (NPOESS), whose first launch is delayed by three years, and whose instruments will be reduced in number and quality.
One instrument that will be lessened is the Conical Scanning Microwave Imager/Sounder (CMIS), designed to collect data on atmospheric conditions to help in weather forecasting.
Its dual measurements would help correct for the atmospheric distortion affecting ground-based observation.
CMIS has been removed and replaced with a less expensive and less capable sensor, contends Christopher Ruf, Professor of Atmospheric, Oceanic and Space Sciences at the University of Michigan.
As a result, it may not have as fine a resolution or be able to correct for atmospheric distortion as well.
"The cheap one will work in clear weather and less well in severe weather," he says, "but the fancy one will work in a hurricane.
"We were excited about that because it would help us improve the tracking of hurricanes, where they make landfall, and the size of the flooding."
Balancing the books
The NRC report says the failure to support Earth-observing systems is part of a larger trend of diminished funding for Earth sciences within Nasa.
By the accountant's sheet, the agency's Earth science budget, which funds Earth-observing missions, appears to be growing; but the NRC found it is actually decreasing. It has fallen by more than a third since 2000, according to Berrien Moore's calculations.
While the President's 2008 Nasa Earth science budget includes a $32.8m boost over last year's allocation, the NRC believes the amount is only a lifeline to beleaguered, already-approved missions such as the delayed Global Precipitation Measurement (GPM) satellite cluster designed to measure planetary rainfall.
The current budget is "totally inadequate" to support the NRC future mission recommendations, says the report.
"Ten years from now, we'll have a less-capable Earth-observing system," comments Scott Denning, an atmospheric scientist at Colorado State University.
NPOESS could provide valuable data on climate and weather
There was concern during hearings in the US Congress that, with an obligation to complete the International Space Station and fulfill other projects, Nasa is trying to do too much.
Nasa Administrator Mike Griffin responded to the NRC study in remarks at the Goddard Space Symposium in March.
He said that, if looked at from 1990, the Nasa Earth science budget has in fact grown, with aeronautical and space technology research losing out.
He labelled the NRC's request for more money as a "brazen recommendation".
"It's hardly brazen to request that the budget be brought back to 2000 levels given how important Earth observing is to the planet," retorts Dr Anthes.
The NRC comments that the Earth science budget remains well below the 2000 funding, even with the president's proposed boost for 2008.
The president's budget includes a five-year projection. After 2010, the trajectory for Earth science funding continues downward.
"By 2012 we go to a 20-year low," says Dr Moore, "and Earth sciences goes in the tank."
He believes the amount of money the NRC budgeted for new satellite missions is the minimum needed to manage and understand the planet. "We don't want to break the bank; we're just saying 'restore the budget to where it was'."
Discussions will continue. The House of Representatives is due to make its budget recommendations in July.