Orbiting Carbon Observatory-2OCO-2
Science 6 March 2009:
Vol. 323. no. 5919, pp. 1276 - 1277
DOI: 10.1126/science.323.5919.1276
Eli Kintisch
With rising temperatures altering a variety of ecological and weather systems on Earth, the current patchwork of sensors can't answer all the questions that scientists are asking. Land-based sensors have provided a conclusive picture of rising CO2 levels worldwide, for example, but researchers don't fully understand where all the carbon that humans and natural sources are pouring into the atmosphere ends up. How much is being absorbed and where?
NASA's Orbiting Carbon Observatory (OCO) was supposed to provide some answers about the nature of carbon sinks on land and in the oceans. But on 24 February, the rocket carrying the $278 million satellite crashed shortly after takeoff, the victim of a failure related to the nose cone. "Bang--it's gone. It was absolutely terrible," says Pieter Tans, an atmospheric scientist at the National Oceanic and Atmospheric Administration's laboratory in Boulder, Colorado. Tans was hoping to improve his four-dimensional maps of CO2 flows--useful to close the global carbon budget--by using OCO's unique ability to detect tiny carbon fluxes.
The loss of OCO is part of a bigger problem of data gaps related to climate. Some gaps, like OCO, rest upon relatively new measurements. In other cases, climate scientists worry that satellites well beyond their operational lifetimes will fail before their replacements are in orbit. Sometimes, as with the monitoring of forest biomass, polar ice, and sea levels, the records go back for decades. "The need for a systematic and comprehensive approach to collecting climate observations has taken on new urgency," concluded a panel from the National Academies in a report issued last week. No single agency or person has the overall authority for the multibillion-dollar challenge of observing Earth's climate, it noted. Researchers are hopeful that a $400 million boost for space-based Earth sensors included in the stimulus package (see p. 1274) will make a difference. But a 2007 academy panel estimated it would cost $6 billion through 2020 to fix a system it said was "at risk of collapse" in 2005.
This backlog exists at a time when better observations are urgently needed, especially at Earth's poles, say researchers. The 2007 report from the Intergovernmental Panel on Climate Change identified basic observations to better understand ice sheet physics as a key requirement for more reliable predictions of sea-level rise. POLENET, an effort to install seismic monitors all over the Antarctic continent, will provide measurements of the temperature of the bedrock on which ice sheets sit, a major factor that affects the speed at which ice slides toward the coast. But bad weather, compounded by rising fuel costs that forced the National Science Foundation to trim spending on polar research, allowed scientists to place only one new station in the field out of 16 originally planned; most operational stations are clustered near McMurdo Station, the main U.S. base on the continent.
The speed at which ice sheets are declining is also governed by the interaction of glaciers with water at the ocean shore. A robotic submarine has recently collected data on the Pine Island Glacier, the fastest moving glacier in Antarctica. Scientists would like a long-term picture of shifting dynamics at the edge of the ice sheet as well as this snapshot. But a project to set up stations on the glacier's edge to monitor the region below the ice was delayed by logistical hurdles: The ice was too rough to allow planes to land on skis, and arranging helicopter facilities wouldn't be possible until the 2011-12 season. "Logistics in Antarctica proceed slowly, [and] we only get to make progress for about 3 months in any year," says NASA's Robert Bindschadler.
Modelers say more data could also clarify the role of atmospheric aerosols in global warming. Aerosols help form clouds, which can both warm and cool the atmosphere. The main sensor on the $14 billion National Polar-orbiting Operational Environmental Satellite System (NPOESS), scheduled for a 2010 launch, will provide aerosol data that will be inferior to data gathered by a sensor on an existing NASA craft called Terra, already 2 years beyond its operational life. In 2007, the National Research Council's (NRC's) decadal study for the field suggested that NASA launch a replacement between 2013 and 2016, and Michael Freilich, NASA's earth sciences chief, says his staff has begun to scope out the mission's requirements. "We're committed to the decadal," he says.
Even Earth-observing mainstays like Landsat are at risk. Landsat 5 and Landsat 7 are both well beyond their nominal design life, regularly missing swaths of images during malfunctions. Scientists who rely on the crafts to study forests' contributions to the carbon cycle say a gap in land imagery is virtually assured because the next satellite in the series, the Landsat Data Continuity Mission, won't be launched before 2012. "We may lose one or both of these satellites before then," says Compton Tucker of the White House Climate Change Science Program (CCSP).
Another problem area is ocean color, a variable that scientists use to measure photosynthesis in the ocean--a giant and poorly understood contributor to the global carbon cycle. NASA's orbiting SeaWiFS sensor has been steadily recording data since 1997. But the instrument is 7 years beyond its design life, and the sensor meant to measure ocean color on the first NPOESS mission will likely be unable to provide sufficient data because of technical problems (Science, 15 February 2008, p. 886). That has spurred some managers to push for a "gap filler" mission sooner, says Tucker. But Freilich is hesitant to commit.
CCSP is leading an interagency effort to finalize a plan that would for the first time provide a set of government priorities for Earth observations, says Tucker. Scientists say that's the first step needed to fill the gaps.
In some cases, international partners might help, he says. Japan's recently launched Greenhouse Gases Observing Satellite, for example, detects CO2 starting at the ground level, like OCO. Although its resolution is lower, it well complements an existing NASA satellite that only picks up CO2 readings at an altitude of 5 km. "We're going to see what we can continue to do with our Japanese partners to fill the gap," says NASA's Stacey Boland.
The effort to better coordinate climate-related monitoring will no doubt be strengthened by the NRC report released last week and presented on 26 February to presidential science adviser John Holdren. Holdren has extolled the virtues of "observation and scientific study of the condition of our home planet's land, vegetation, oceans, and atmosphere." Climate researchers are hoping those words, delivered at his confirmation hearing to be director of the White House Office of Science and Technology Policy, will soon translate into support for filling the holes in the nation's current Earth-monitoring system.