NASA Carbon Cycle & Ecosystems Joint Science Workshop 28 April - 2 May 2008

1. Active Sensing of CO2 Emissions over Nights, Days, & Seasons (ASCENDS) Berrien Moore IIIClimate Central Princeton, NJ &University of New Hampshire NASA Carbon Cycle & Ecosystems Joint Science Workshop 28 April - 2 May 2008

2. Active Sensing of CO2 Emissionsover Nights, Days, and Seasons (ASCENDS)Launch: 2013-2016Mission Size: Medium ASCENDS provides a highly precise global dataset for atmospheric CO2 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 CO2.

3. Orbiting Carbon Observatory - JPL

4. Anthropogenic C Emissions: Fossil Fuel 2006 Fossil Fuel:8.4 Pg C [2006-Total Anthrop. Emissions: 8.4+1.5 = 9.9 Pg] 1850 1870 1890 1910 1930 1950 1970 1990 2010 • 1990 - 1999:1.3%y-1 • 2000 - 2006:3.3% y-1 Raupach et al. 2007, PNAS; Canadell et al 2007, PNAS

5. 2006 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% Observed 2000-2006 3.3% Raupach et al. 2007, PNAS; Canadell et al 2007, PNAS

6. The Airborne Fraction (2000-2006) 45% of all CO2 emissions accumulated in the atmosphere The Airborne Fraction The fraction of the annual anthropogenic emissions that remains in the atmosphere 55% were removed by natural sinks Ocean removes 24% Land removes 30% Canadell et a.l, 2007, PNAS

7. [CO2] 1850 1870 1890 1910 1930 1950 1970 1990 2010 Atmospheric CO2 Concentration Year 2006 Atmospheric CO2 concentration: 381 ppm 35% above pre-industrial • 1970 – 1979: 1.3 ppm y-1 1980 – 1989: 1.6 ppm y1 • 1990 – 1999: 1.5 ppm y-1 • 2000 - 2006:1.9 ppmy-1 NOAA 2007,Canadell et al., 2007, PNAS

8. Attribution of Recent Acceleration of Atmospheric CO2 • 1970 – 1979: 1.3 ppm y-1 1980 – 1989: 1.6 ppm y1 • 1990 – 1999: 1.5 ppm y-1 • To: • Economic growth • Carbon intensity • Efficiency of natural sinks • 2000 - 2006:1.9 ppmy-1 65% - Increased activity of the global economy 17% - Increased carbon intensity of the global economy 18% - Decreased efficiency of natural sinks Canadell et al., 2007, PNAS

9. Impact of Stabilizing Emissions versus Sabilizing Concentrations of CO2

10. Global CarbonSourcesandSinks Source: GCTE / IGBP

11. Science Questions How is the Earth's carbon cycle changing? What are the spatial and temporal patterns of exchange of CO2 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 CO2 with sufficient precision to allow accurate determination of spatial and temporal pattern of the sources and sinks of CO2. The CARBON CYCLE. Carbon in the atmosphere is a controlling factor on climate and hence on ecological productivity and the sustainability of life.

12. 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 CO2 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

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

14. Importance of the Science Questions Large uncertainties remain about the size of the oceanic sink. Recent evidence suggests that the Southern Ocean sink may be saturating. Oceanic uptake of CO2 increases the acidity of the ocean with unknown ecological effects. ASCENDS will resolve the geographical and temporal patterns of oceanic sources and sinks. Global Carbon Budget(IPCC, 2007)

15. Average Error Reduction Land: 40% Ocean: 13% Total: 20% Fractional Error Reduction Science Rationale Science Measurement Requirements • ASCENDS CO2 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 CO2 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. ASCENDS will make major contribution to knowledge of CO2 sources & sinks.

16. Pressure Altitude (km) Latitude Active Sensing of CO2 Emissions over Nights, Days, & Seasons (ASCENDS) Mission Objectives Airborne Demonstration Day/Night Global CO2 Column Measurements Airborne Test Flights • Approach • ASCENDS will deliver laser based remote sensing measurements of CO2 mixing ratios (XCO2) • Day and night • At all latitudes • During all seasons • ASCENDS includes simultaneous measurements of • CO2 number density (ND) tropospheric column • O2 ND column: surface pressure for CO2 to XCO2 • Temperature profile: improved CO2 accuracy • Altimetry: surface elevation, cloud top heights • CO profile: identify combustion sources of CO2 • 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 2013-2016 to overlap with OCO (OCO scheduled launch: Dec 2008) • Data have been collected from airborne instruments to verify the CO2 measurement capability of the laser based approach

17. Payload CO2 column mixing ratio (XCO2) measurement with Laser Absorption Spectrometer (LAS) technique requires the simultaneous measurement of the CO2 column number density (CND); the O2 column number density to converting the CND to XCO2; and the path length of the measurement. A temperature profile measurement is also required to constrain the XCO2 measurement. A column CO measurement over the same XCO2 path is also recommended for interpreting sources and sinks of CO2. • CO2 column measurement • CO2Laser Absorption Spectrometer to resolve (or weight) the CO2 altitude distribution, particularly across the mid to lower troposphere. • 1.6 µm LAS only baseline • Integrated 1.6 µm + 2.0 µm • Surface pressure measurement • O2 Laser Absorption Spectrometer to convert CO2 number density to mixing ratio. • Surface/cloud top altimeter • Laser altimeter to measure CO2 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.

19. 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.