NASA Carbon Cycle & Ecosystems Joint Science Workshop 28 April - 2 May 2008 Berrien Moore III Climate Central Princeton, NJ & University of New Hampshire Active Sensing of CO 2 Emissions over Nights, Days, & Seasons (ASCENDS)

Active Sensing of CO 2 Emissions over Nights, Days, and Seasons (ASCENDS) Launch: Mission Size: Medium ASCENDS provides a highly precise global dataset for atmospheric CO 2 column measurements without seasonal, latitudinal, or diurnal bias. This will quantify the regional carbon sources/sinks and thereby increase understanding of the underlying mechanisms are central to prediction of future levels of CO 2.

Orbiting Carbon Observatory - JPL

Anthropogenic C Emissions: Fossil Fuel : 1.3% y : 3.3% y Fossil Fuel: 8.4 Pg C [2006-Total Anthrop. Emissions: = 9.9 Pg] Raupach et al. 2007, PNAS; Canadell et al 2007, PNAS

Trajectory of Global Fossil Fuel Emissions 50-year constant growth rates to 2050 B1 1.1%, A1B 1.7%, A2 1.8% A1FI 2.4% 2006 Observed % Raupach et al. 2007, PNAS; Canadell et al 2007, PNAS

The Airborne Fraction ( ) Ocean removes 24% Land removes 30% 55% were removed by natural sinks 45% of all CO 2 emissions accumulated in the atmosphere The Airborne Fraction The fraction of the annual anthropogenic emissions that remains in the atmosphere Canadell et a.l, 2007, PNAS

Atmospheric CO 2 Concentration : 1.9 ppm y – 1979: 1.3 ppm y – 1989: 1.6 ppm y – 1999: 1.5 ppm y -1 Year 2006 Atmospheric CO 2 concentration: 381 ppm 35% above pre-industrial [CO 2 ] NOAA 2007, Canadell et al., 2007, PNAS

65% - Increased activity of the global economy 17% - Increased carbon intensity of the global economy 18% - Decreased efficiency of natural sinks Attribution of Recent Acceleration of Atmospheric CO 2 To: Economic growth Carbon intensity Efficiency of natural sinks Canadell et al., 2007, PNAS : 1.9 ppm y – 1979: 1.3 ppm y – 1989: 1.6 ppm y – 1999: 1.5 ppm y -1

Impact of Stabilizing Emissions versus Sabilizing Concentrations of CO 2

Global Carbon Sources and Sinks Source: GCTE / IGBP

Science Questions How is the Earth's carbon cycle changing? What are the spatial and temporal patterns of exchange of CO 2 between the atmosphere and the surface, and how are these patterns affected by large scale modes in weather-climate, and how are these patterns affected by human actions? What are the feedbacks of climate on the carbon cycle, and what are the likely effects on the carbon cycle of these feedbacks in the future? This mission will make measurements day and night at all latitudes in all seasons of total column mixing ratio of CO 2 with sufficient precision to allow accurate determination of spatial and temporal pattern of the sources and sinks of CO 2. The CARBON CYCLE. Carbon in the atmosphere is a controlling factor on climate and hence on ecological productivity and the sustainability of life.

Challenges Posed by the Science Questions Because of spatial and temporal variability, practical determination of the pattern of sources and sinks from surface measurements is impossible. The only viable approach is to infer aspects of the rates of exchange by inverting the causal relation between source-sinks and atmospheric concentration. This requires measurements of total column CO 2 with high precision measurements in all seasons and all latitudes with a focus upon mid to lower troposphere, under a varying set of large-scale weather-climate modes. MODIS

ASCENDS will reduce major uncertainties and help explain the “missing carbon sink” and its dynamics. Global Carbon Budget (IPCC, 2007) The largest uncertainties about the Earth’s carbon budget are in its terrestrial components; land biosphere is the most vulnerable carbon pool. Importance of the Science Questions

ASCENDS will resolve the geographical and temporal patterns of oceanic sources and sinks. Large uncertainties remain about the size of the oceanic sink. Recent evidence suggests that the Southern Ocean sink may be saturating. Oceanic uptake of CO 2 increases the acidity of the ocean with unknown ecological effects. Global Carbon Budget (IPCC, 2007) Importance of the Science Questions

Science Rationale Science Measurement Requirements ASCENDS CO 2 Measurement Requirements derived from Observing System Simulation Experiments (OSSEs) conducted by Peter Rayner and Frédéric Chevallier, CEA-CNRS. Assumed measurement precision for 100-km tropospheric CO 2 column measurement over land of 1.3 ppmv during day and 0.8 ppmv at night and over water of 4.2 ppmv during day and 2.1 during night. Fractional Error Reduction ASCENDS will make major contribution to knowledge of CO 2 sources & sinks. Average Error Reduction Land: 40% Ocean: 13% Total:20%

Airborne Test Flights Approach ASCENDS will deliver laser based remote sensing measurements of CO 2 mixing ratios (XCO 2 ) Day and night At all latitudes During all seasons ASCENDS includes simultaneous measurements of CO 2 number density (ND) tropospheric column O 2 ND column: surface pressure for CO 2 to XCO 2 Temperature profile: improved CO 2 accuracy Altimetry: surface elevation, cloud top heights CO profile: identify combustion sources of CO 2 ASCENDS will be a logical extension of OCO and GOSAT capabilities Summary ASCENDS identified as a medium size mission in the NRC Decadal Survey LRD to overlap with OCO (OCO scheduled launch: Dec 2008) Data have been collected from airborne instruments to verify the CO 2 measurement capability of the laser based approach Mission Objectives Day/Night Global CO 2 Column Measurements Airborne Demonstration Pressure Altitude (km) Latitude Active Sensing of CO 2 Emissions over Nights, Days, & Seasons (ASCENDS)

Payload CO 2 column measurement CO 2 Laser Absorption Spectrometer to resolve (or weight) the CO 2 altitude distribution, particularly across the mid to lower troposphere. 1.6 µm LAS only baseline Integrated 1.6 µm µm Surface pressure measurement O 2 Laser Absorption Spectrometer to convert CO 2 number density to mixing ratio. Surface/cloud top altimeter Laser altimeter to measure CO 2 column length. Temperature sounder Six channel passive radiometer to provide temperature corrections. CO sensor Gas Filter Correlation Radiometers (at 2.3 & 4.6 µm) to separate biogenetic fluxes from biomass burning and fossil fuel combustion. Imager To provide cloud clearing for soundings. CO 2 column mixing ratio (XCO 2 ) measurement with Laser Absorption Spectrometer (LAS) technique requires the simultaneous measurement of the CO 2 column number density (CND); the O 2 column number density to converting the CND to XCO 2 ; and the path length of the measurement. A temperature profile measurement is also required to constrain the XCO 2 measurement. A column CO measurement over the same XCO 2 path is also recommended for interpreting sources and sinks of CO 2.

Key Mission Milestones Pre-Phase A: Present – April 2010 Start Phase A: April 2010 Confirmation: April 2012 Payload Delivery: April 2014 Satellite Ship: September 2015 Launch: October 2015 End of Primary Mission (3 years): October 2018 Note: Earlier launch (August 2014) is technically feasible if prior year implementation funding is provided.