Some questions in current climate and CO 2 studies

1. Some questions in current climate and CO2 studies

2. Some questions in current climate and CO2 studies • How big are the global land and ocean sinks? • Given that they are variable, can we specify them with sufficient accuracy to be useful in “Kyoto accounting” • What confidence can we have in predictions of their size over (say) the next 200 years?

3. Accumulation in atmosphere 3.3 Pg C yr-1 1980s budget of anthropogenic carbon dioxide. Land uptake? (1.9 by difference) Deforestation 1.7 Pg C yr-1? Fossil fuel release 5.4 Pg C yr-1 Ocean uptake 1.9 Pg C yr-1

4. The Mauna Loa atmospheric record. C. Dave Keeling Late 1990s measurement network

5. Fossil Fuel Emissions • Well quantified from econometric data (Marland, Andres)

6. Size of the land and ocean sinks • The total sink is known from accurate fossil fuel emission data and atmospheric accumulation rates. • Two methods to separate land and ocean sinks: • Calculate ocean sink from models and obtain net land by difference (IPCC assessments 1 and 2) • Use atmospheric O2/N2 measurements in the atmosphere to separate land and ocean. (IPCC assessment 3).

7. Comparison of North Atlantic annual average pCO2 with multiple models.

8. Oxygen and CO2 Comparison

9. “Keeling’s method” Diagnose size of land and ocean sinks Use known (?) molar ratios of O2 / CO2 change for Fossil fuel burning land uptake / release by vegetation Ocean uptake. Global average concentrations of O2 vs CO2

10. How well is the global ocean sink known? Estimates of the global ocean sink 1990-1999 Reference Sink (GtC yr-1) IPCC (2001) 1.7+/- 0.5 Estimate (O2- CO2 method.) OCMIP-2 Model 2.5+/- 0.4 Intercomparison (ten ocean carbon models).

11. Variability in the ocean and land sinks

12. Variation in the growth rate of atmospheric CO2, 1957-1999 • Rate of growth is highly variable – not due to change in fossil fuel source. • Variation correlates with Southern oscillation – El Ninos. • Indicates the “Natural” sinks for atmospheric CO2 are highly variable. • Though the land sink dominates variability, ocean is also important

13. Estimates of the ocean sink variability

14. 90 3 0 -3 0 -90 -180 -120 -60 0 60 120 180 Atmospheric Inversion calculations of CO2 sources and sinks • Discrimination of sources/sinks between latitude bands is relatively easy • Localising sinks in the same latitude bands is subject to wide error. • Fluxes over ocean basins are than easier to constrain than continental fluxes over large regions.

17. Greenland-Denmark New York–Halifax-Hamburg Caribbean – Portsmouth South-America-Spain 90°W 50°W 10°W Ship-of-Opportunity routes North Atlantic Carbon Observing System Cruise tracks CAVASSOO 2001 – 2003 EU project

18. Surface pCO2, nutrient and surface temperature in the North Atlantic 360 Mar Apr May Jun Jul Aug Sep Oct 340 320 ) atm m ( 300 2 pCO 2 pCO 280 260

19. Comparison of recent, well-resolved data with models. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

20. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

21. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

22. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

23. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

24. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

25. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

26. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

27. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

28. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

29. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

30. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

31. Cavassoo data from I.F.M., University of Kiel (Wallace, Koertzinger et al).

32. Remote sensing of SST, Ocean colour to enable Interpolation/ extrapolation of surface CO2 observations

33. What confidence can we have in predictions of future carbon sinks?

34. Seasonal model-data intercomparison – Hamburg-NewYork Models: Jim Orr, LSCE And OCMIP-2 members Data: CAVASSOO, CASIX OCMIP2 models vs data Mean of models vs data Models are forced with mean climatological data.

35. Seasonal model-data intercomparison – Hamburg-NewYork Models: Jim Orr, LSCE And OCMIP-2 members Data: CAVASSOO, IFM group. OCMIP2 models vs data Mean of models vs data Models are forced with mean climatological data.

37. Possible Marine biological effects on Carbon uptake, next 100 years. Iron fertilisation -- deliberate or inadvertent NO3 fertilisation pH change mediates against calcite- precipitating organisms Reduction in THC offset by increased efficiency of nutrient utilisation Other unforeseen ecosystem changes Process Effect on CO2 uptake ?

38. Iron and Kyoto: • At present the land is a source of iron to the ocean. • Efforts to sequester carbon on land will change that source.

43. Ridgwell, A. J. et al, Geophys. Res. Lett. (2002)