Expert and Government Review Comments on the IPCC WGI AR5 Second Order Draft – Chapter 2 Comment Chapter From From To To No Page Line Page Line Comment Response 2-1 2 0 0 0 0 First of all I want to convey my sincere admiration to the authors for attempting such a difficult enterprise as is Thanks reviewing all the scientific literature on atmospheric and surface observations. This task is made even more daunting (both from a scientific and writing viewpoint) by the mandate to build on the earlier AR4 report and the need to interpret differences therefrom. Not only does the text become inevitably repetitive, but the authors have had to constantly assess whether the most recent studies support earlier conclusions and what constitutes sufficient evidence to revise or question earlier statements. While I am fully aware of these major difficulties, I still think that the current draft feels rough and of uneven quality, with a lack of consistency (in background scientific information provided, length, level of regional detail, treatment of statistical significance, presence of error bars in graphics, summary statements) from section to section. The precipitation, surface humidity and cloud sections, in particular, seem incomplete. Some lack of uniformity is due to the fact that research has not progressed at the same rate in all observational fields; a a result, while some sections report significant improvements in our understanding, others simply list a myriad of varied regional results that cannot be interpreted in any particular way (is it necessary then to list them?). There are also several places where insufficient effort to assessing (as opposed to listing) results has been paid. From an editing perspective, I must also recommend that the authors undertake a thorough revision of the entire document looking to improve its readability and usefulness to a graduate student, post-doc or scientist not expert in the particular field itself. Currently the document is rather difficult to parse even for an interested reviewer. My take may be flawed but I am thinking of this document as something one could refer a graduate student to in order for him/her to gain an overview on a particular topic. There is a surprising absence of connecting words within paragraphs whose presence would allow the reader to follow the flow of ideas and gain a clearer notion of what the ovrall results mean (by the time the summary sentence arrives, the reader is sometimes at loss). In fact I wonder if there was a deliberate effort to postpone the “narrative touches” until the final draft. In places, the document also seems to be lacking an organized story (with some undesirable jumps, backtracking and repetitions within the text). [Ileana Bladé, Spain] 2-2 2 0 0 0 0 Chapter 2 reports new work on the global abundance and trends of all the important greenhouse gases Rejected - outside scope of Chapter 2. (GHGs), however there are no citations to papers describing and using the isotopic composition and trends of GHGs, a likely more important source of information about GHG sources and sinks than the abundance and trend data. This research could be reviewed in Chapter 6. Please ensure that these papers are reviewed in either Chapter 2 or Chapter 6. The GHG isotope variation papers that should be discussed are: Allison, C. & R. Francey, Verifying global trends in atmospheric carbon dioxide stable isotopes, J. Geophys. Res., 112, D21304, doi:10.1029/2006JD007345, 2007. Rayner, P., R. Law, C. Allison, R. Francey, C. Trudinger & C. Pickett-Heaps, The inter-annual variability of the global carbon cycle (1992-2005) inferred by inversion of atmospheric CO2 and δ13CO2, Global Biogeochem. Cycles, 22, GB3008, doi:10.1029/2007GB003068, 2008 Levin, I., T. Naegler, B. Kromer, M. Diehl, R. Francey, A. Gomez-Pelaez, P. Steele, D. Wagenbach, R. Weller & D. Worthy, Observations and modelling of the global distribution and long-term trend of atmospheric 14CO2, Tellus B, 62(1), 26-46, 2010 Welp, L., .....R. Francey, C. Allison et al., El Nino effects on the isotopic composition of oxygen in atmospheric CO2, Nature, 477, 579-582, 2011 Ferretti, D., J. Miller, J. White, K. Lassey, D. Lowe & D. Etheridge, Stable isotopes provide revised global limits of aerobic methane emissions from plants, Atmospheric Chemistry and Physics, 7, 237-241, 2007. Petrenko, V., D. Etheridge, R. Weiss, E. Brook, H. Schaefer, J. Severinghaus, A. Smith, D. Lowe, Q. Hua & K. Riedel, Methane from the East Siberian Arctic Shelf, Science, 329, 1146-1147, 2010 Park, S., D. Etheridge, P. Fraser, P. Krummel, R. Langenfelds, P. Steele, C. Trudinger et al., Trends and seasonal cycles in the isotopic composition of nitrous oxide since 1940, Nature Geosciences,5, 261-265, 2012 [Government of Australia] 2-3 2 0 0 0 0 Papers on greenhouse gas trends, sources and sinks that should be reviewed in Chapter 2 or Chapter 6: Rejected - outside scope of Chapter 2. Francey, R., C. Trudinger, M. van der Schoot, P. Krummel, P. Steele & R. Langenfelds, Differences between trends in atmospheric CO2 and the reported trends in anthropogenic CO2 emissions, Tellus B, 62: 316–328, doi: 10.1111/j.1600-0889.2010.00472.x, 2010 - this is an important paper because it describes an apparent inconsistency between 'bottom-up' and 'top-down' estimates of fossil fuel CO2 emissions. Do not Cite, Quote or Distribute Page 1 of 235 Expert and Government Review Comments on the IPCC WGI AR5 Second Order Draft – Chapter 2 Comment Chapter From From To To No Page Line Page Line Comment Response Pan, Y., .....J. Canadell, et al., A large and persistent carbon sink in the world’s forests, 1990-2007, Science, 333, 988-993, 2011 Peters, G., .....J. Canadell. M. Raupach et al., Rapid growth in CO2 emissions after the 2008-2009 global financial crisis, Nature Climate Change, 2, 2-4, 2012 Raupach, M., J. Canadell & C. Le Quere, Anthropogenic and biophysical contributors to increasing atmospheric CO2 growth rate and airborne fraction, Biogeosciences, 5, 1601-1613, 2008 Raupach, M., Pinning down the land carbon sink. Nature Climate Change, 1(3), 148-149, 2011 Le Quéré, C., C. Rodenbeck, E. Buitenhuis, T. Conway, R. Langenfelds, A. Gomez, C. Labuschagne, M. Ramonet, T. Nakazawa, N. Metzl, N. Gillett & M. Heimann, Saturation of the Southern Ocean CO2 sink due to recent climate change, Science, 316, 1735-1738, 2007 Le Quere, C., C. Rodenbeck, E. Buitenhuis, T. Conway, R. Langenfelds, A. Gomez, C. Labus change, M. Ramonet, T. Nakazawa, N. Metzl, N. Gillett & M. Heimann, Response to Comments on ‘Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change’, Science, 319, doi:10.1126/science.1147315, 2008. Law, R., R. Matear & R. Francey, Comment on ‘Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change, Science, 319, doi: 10.1126/science.1149077, 2008. Patra, P., M. Takigawa, K. Ishijima, B.-C. Choi, D. Cunnold, E. Dlugokencky, P. Fraser, A. Gomez-Pelaez, T.- Y. Goo, J.-S. Kim, P. Krummel, R. Langenfelds, F. Meinhardt, H. Mukai, S. O’Doherty, R. Prinn, P. Simmonds, P. Steele, Y. Tohjima, K. Tsuboi, K. Uhse, R. Weiss, D. Worthy & T. Nakazawa, Growth rate, seasonal, synoptic & diurnal variations and budget of methane in lower atmosphere, J. Meteorological Society of Japan, 87:4, 635-663, 2009 Patra, P., .....R. Law, Z. Loh, et al., , TransCom model simulations of CH4 and related species: linking transport, surface flux and chemical loss with CH4 variability in the troposphere and lower stratosphere, Atmos. Chem. Phys., 11, 12813-12837, 2011. Le Quéré, C., M. Raupach, J. Canadell, G. Marland, L. Bopp, P. Ciais, T. Conway, S. Doney, R. Feely, P. Friedlingstein, K. Gurney, R. Houghton, J. House, C. Huntingford, P. Levy, M. Lomas, J. Majkut, N. Metzl, J. Ometto, G. Peters, C. Prentice, J. Randerson, S. Running, J. Sarmiento, U. Schuster, S. Sitch, T. Takahashi, N. Viovy, G. van der Werf & I. Woodward, , Trends in the sources and sinks of carbon dioxide, Nature Geosciences, 2, doi:10.1038/ngeo689, 2009 Chevallier, F., P. Ciais , T. Conway, T. Aalto, B. Anderson, P. Bousquet, E. Brunke, L. Ciattaglia, Y. Esaki, M. Fröhlich, A. Gomez-Pelaez, L. Haszpra, P. Krummel, R. Langenfelds, M. Leuenberger, T. Machida, F. Maignan, H. Matsueda, J-A. Morguí, H. Mukai, T. Nakazawa, P. Peylin, M. Ramonet, L. Rivier, Y. Sawa, M. Schmidt, P. Steele, S. Vay, A. Vermeulen, S. Wofsy & D. Worthy: CO2 surface fluxes at grid point scale estimated from a global 21-year reanalysis of atmospheric measurements, J. Geophys. Res., 115, D21307,doi:10.1029/2010JD013887, 2010 [Government of Australia] 2-4 2 0 0 0 0 Papers on long-term ice core CO2 record that should be reviewed in Chapter 2 or Chapter 5 include: Rejected - outside scope of Chapter 2. Ahn, J., .....D. Etheridge, M. Rubino et al., Atmospheric CO2 over the last 1000 years: a high resolution record from the West Antarctic Ice Sheet (WAIS) Divide ice core, Global Biogeochemical Cycles, 26, GB2027, doi:10.1029/2011GB004247, 2012 Other ice core/firn papers that need to be reviewed in Chapter 2 or Chapter 5: Worton et al., CF4, C2F6, Environ. Sci. Tech., 41, 2184-2189, 2007 (may have been reviewed in the 4th Assessment) Witrant et al., trace gases in firn, Atmos. Chem. Phys. Disc., 11, 23029-23080, 2011 Buizert et al., trace gases in Greenland ice core, Atmos. Chem. Phys. Disc.,11, 15975-16021, 2011 [Government of Australia] 2-5 2 0 0 0 0 Important paper on CFC lifetimes that should be included in Chapter 2: Rejected - outside scope of Chapter 2. Do not Cite, Quote or Distribute Page 2 of 235 Expert and Government Review Comments on the IPCC WGI AR5 Second Order Draft – Chapter 2 Comment Chapter From From To To No Page Line Page Line Comment Response Rigby, M., .....P.