AGW Observer

Observations of anthropogenic global warming

New research from last week 7/2011

Posted by Ari Jokimäki on February 21, 2011

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Anthropogenic ocean acidification shows in Bering Sea

Coupling primary production and terrestrial runoff to ocean acidification and carbonate mineral suppression in the eastern Bering Sea – Mathis et al. (2011) “Water column pH and carbonate mineral saturation states were calculated from dissolved inorganic carbon (DIC) and total alkalinity data collected over the eastern Bering Sea shelf in the spring and summer of 2008. The saturation states (Ω) of the two most important carbonate minerals, calcite (Ωcalcite) and aragonite (Ωaragonite) were strongly coupled to terrestrial runoff from the Yukon and Kuskokwim rivers, primary production in the surface waters, and remineralization of organic matter at depth over the shelf. In spring, before ice melt occurred, pH over the shelf was largely confined to a range of 7.9–8.1 and Ωcalcite and Ωaragonite ranged from 1.5 to 3.0 and 0.8 to 2.0, respectively. At the stations closest to river outflows, aragonite was undersaturated in the water column from the surface to the bottom. During the summer sea ice retreat, high rates of primary production consumed DIC in the mixed layer, which increased pH and Ωcalcite and Ωaragonite. However, Ωcalcite and Ωaragonite decreased by ∼0.3 in the bottom waters over the middle and outer shelf. Over the northern shelf, where export production is highest, Ωaragonite decreased by ∼0.35 and became highly undersaturated. The observed suppression and undersaturation of Ωcalcite and Ωaragonite in the eastern Bering Sea are correlated with anthropogenic carbon dioxide uptake into the ocean and will likely be exacerbated under business-as-usual emission scenarios. Therefore, ocean acidification could threaten some benthic and pelagic calcifying organisms across the Bering Sea shelf in the coming decades.” Mathis, J. T., J. N. Cross, and N. R. Bates (2011), Coupling primary production and terrestrial runoff to ocean acidification and carbonate mineral suppression in the eastern Bering Sea, J. Geophys. Res., 116, C02030, doi:10.1029/2010JC006453. [full text]

New estimate shows ocean’s biological carbon pump weaker

A reduced estimate of the strength of the ocean’s biological carbon pump – Henson et al. (2011) “A major term in the global carbon cycle is the ocean’s biological carbon pump which is dominated by sinking of small organic particles from the surface ocean to its interior. Several different approaches to estimating the magnitude of the pump have been used, yielding a large range of estimates. Here, we use an alternative methodology, a thorium isotope tracer, that provides direct estimates of particulate organic carbon export. A large database of thorium-derived export measurements was compiled and extrapolated to the global scale by correlation with satellite sea surface temperature fields. Our estimates of export efficiency are significantly lower than those derived from the f-ratio, and we estimate global integrated carbon export as ∼5 GtC yr−1, lower than most current estimates. The lack of consensus amongst different methodologies on the strength of the biological carbon pump emphasises that our knowledge of a major planetary carbon flux remains incomplete.” Henson, S. A., R. Sanders, E. Madsen, P. J. Morris, F. Le Moigne, and G. D. Quartly (2011), Geophys. Res. Lett., 38, L04606, doi:10.1029/2011GL046735. [full text]

Debate on prehistoric land use effects continues

Modelling prehistoric land use and carbon budgets: A critical review – Boyle et al. (2011) “An evaluation of modelled estimates for C release following early land clearance at the global level based on new model assumptions suggests that earlier studies may have underestimated its magnitude, chiefly because of underestimation of the mid-Holocene global population. Alternative information sources for population and land utilisation support both a greater total CO2 release and a greater Neolithic contribution. Indeed, we show that the quantity of terrestrial C release due to early farming, even using the most conservative assumptions, greatly exceeds the net terrestrial C release estimated by inverse modelling of ice core data by Elsig et al. (Elsig J, Schmitt J, Leuenberger D, Schneider R, Eyer M, Leuenberger M et al. (2009) Stable isotope constraints on Holocene carbon cycle changes from an Antarctic ice core. Nature 461: 507–510), though uncertainty about past global population estimates precludes calculation of a precise value.” John F. Boyle, Marie-José Gaillard, Jed O. Kaplan, John A. Dearing, The Holocene February 17, 2011, doi: 10.1177/0959683610386984.

Tropical corals in Japan expanding polewards 14 km/year

Rapid poleward range expansion of tropical reef corals in response to rising sea surface temperatures – Yamano et al. (2011) “Rising temperatures caused by climatic warming may cause poleward range shifts and/or expansions in species distribution. Tropical reef corals (hereafter corals) are some of the world’s most important species, being not only primary producers, but also habitat-forming species, and thus fundamental ecosystem modification is expected according to changes in their distribution. Although most studies of climate change effects on corals have focused on temperature-induced coral bleaching in tropical areas, poleward range shifts and/or expansions may also occur in temperate areas. We show the first large-scale evidence of the poleward range expansion of modern corals, based on 80 years of national records from the temperate areas of Japan, where century-long measurements of in situ sea-surface temperatures have shown statistically significant rises. Four major coral species categories, including two key species for reef formation in tropical areas, showed poleward range expansions since the 1930s, whereas no species demonstrated southward range shrinkage or local extinction. The speed of these expansions reached up to 14 km/year, which is far greater than that for other species. Our results, in combination with recent findings suggesting range expansions of tropical coral-reef associated organisms, strongly suggest that rapid, fundamental modifications of temperate coastal ecosystems could be in progress.” Yamano, H., K. Sugihara, and K. Nomura (2011), Geophys. Res. Lett., 38, L04601, doi:10.1029/2010GL046474.

Methane concentration might be rising again

Global column-averaged methane mixing ratios from 2003 to 2009 as derived from SCIAMACHY: Trends and variability – Frankenberg et al. (2011) “After a decade of stable or slightly decreasing global methane concentrations, ground-based in situ data show that CH4 began increasing again in 2007 and that this increase continued through 2009. So far, space-based retrievals sensitive to the lower troposphere in the time period under consideration have not been available. Here we report a long-term data set of column-averaged methane mixing ratios retrieved from spectra of the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) instrument onboard Envisat. The retrieval quality after 2005 was severely affected by degrading detector pixels within the methane 2ν3 absorption band. We identified the most crucial problems in SCIAMACHY detector degradation and overcame the problem by applying a strict pixel mask as well as a new dark current characterization. Even though retrieval precision after the end of 2005 is invariably degraded, consistent methane retrievals from 2003 through 2009 are now possible. Regional time series in the Sahara, Australia, tropical Africa, South America, and Asia show the methane increase in 2007–2009, but we cannot yet draw a firm conclusion concerning the origin of the increase. Tropical Africa even seems to exhibit a negative anomaly in 2006, but an impact from changes in SCIAMACHY detector degradation cannot be excluded yet. Over Assakrem, Algeria, we observed strong similarities between SCIAMACHY measurements and ground-based data in deseasonalized time series. We further show long-term SCIAMACHY xCH4 averages at high spatial resolution that provide further insight into methane variations on regional scales. The Red Basin in China exhibits, on average, the highest methane abundance worldwide, while other localized features such as the Sudd wetlands in southern Sudan can also be identified in SCIAMACHY xCH4 averages.” Frankenberg, C., I. Aben, P. Bergamaschi, E. J. Dlugokencky, R. van Hees, S. Houweling, P. van der Meer, R. Snel, and P. Tol (2011), J. Geophys. Res., 116, D04302, doi:10.1029/2010JD014849.

A forest changes its CO2 exchange with climate variability

Relationships between large-scale circulation patterns and carbon dioxide exchange by a deciduous forest – Zhang et al. (2011) “In this study, we focus on a deciduous forest in central Massachusetts and investigate the relationships between global climate indices and CO2 exchange using eddy-covariance flux measurements from 1992 to 2007. Results suggest that large-scale circulation patterns influence the annual CO2 exchange in the forest through their effects on the local surface climate. Annual gross ecosystem exchange (GEE) in the forest is closely associated with spring El Niño–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO), previous fall Atlantic Multidecadal Oscillation (AMO), and previous winter East Pacific–North Pacific (EP-NP) pattern. Annual net ecosystem exchange (NEE) responds to previous fall AMO and PDO, while annual respiration (R) is impacted by previous fall ENSO and Pacific/North American Oscillation (PNA). Regressions based on these relationships are developed to simulate the annual GEE, NEE, and R. To avoid problems of multicollinearity, we compute a “Composite Index for GEE (CIGEE)” based on a linear combination of spring ENSO and PDO, fall AMO, and winter EP-NP and a “Composite Index for R (CIR)” based on a linear combination of fall ENSO and PNA. CIGEE, CIR, and fall AMO and PDO can explain 41, 27, and 40% of the variance of the annual GEE, R, and NEE, respectively. We further apply the methodology to two other northern midlatitude forests and find that interannual variabilities in NEE of the two forests are largely controlled by large-scale circulation patterns. This study suggests that global climate indices provide the potential for predicting CO2 exchange variability in the northern midlatitude forests.” Zhang, J., L. Wu, G. Huang, and M. Notaro (2011), J. Geophys. Res., 116, D04102, doi:10.1029/2010JD014738.

Not much long-term trend in El Niño according to new reanalysis

El Niño variability in simple ocean data assimilation (SODA), 1871–2008 – Giese & Ray (2011) “A new ocean reanalysis that covers the period from 1871 to 2008 is used to explore the time-evolving characteristics of El Niño. The new reanalysis assimilates all available hydrographic and sea surface temperature data into a model of the global ocean forced with surface boundary conditions from an atmospheric reanalysis that also covers the period from 1871 through 2008. Using traditional measures of El Niño, our reanalysis shows that the timing of El Niño events is in agreement with sea surface temperature reconstructions, but El Niño in the reanalysis is stronger, particularly from 1871 to 1920. A new index based on the first moment of the temperature anomaly is introduced. The new index is used to characterize the strength and location of El Niño events and has the advantage that it is independent of the location of El Niño. Using the new index, El Niño in the reanalysis shows prominent decadal variability of strength but relatively little long-term trend. El Niño events were strong in the last part of the 19th century and first part of the 20th century and again in the latter part of the 20th century, with weak El Niño events in the middle of the 20th century. The location of El Niño also varies considerably, ranging from the western to the eastern Pacific near the coast of South America. However, the null hypothesis that the location of El Niño can be represented as a random distribution about a central longitude of about 140°W cannot be rejected.” Giese, B. S., and S. Ray (2011), J. Geophys. Res., 116, C02024, doi:10.1029/2010JC006695.

Estimate of global CO2 emissions from volcanic lakes

Global CO2 emission from volcanic lakes – Pérez et al. (2011) “The global CO2 discharge from subaerial volcanism has been estimated at ~300 Mt yr−1. However, estimates of CO2 emissions from volcanic lakes have not been considered. In order to improve this information, extensive research on CO2 emissions of volcanic lakes worldwide has been performed. The observed normalized average CO2 emission rates increase from alkaline (5.5 t km−2 d−1), to neutral (201.2 t km−2 d−1), to acid (614.2 t km−2 d−1) in volcanic lakes. Taking into account (1) normalized CO2 emission rates, (2) the number of volcanic lakes in the world (~769), and (3) the fraction and average areas of the investigated alkaline, neutral, and acid volcanic lakes, the estimated global CO2 emission from volcanic lakes is 117 ± 19 Mt yr−1, with 94 ± 17 Mt yr−1 as deep-seated CO2. This study highlights the importance of a revision of the actual global CO2 discharge from subaerial volcanism.” Nemesio M. Pérez, Pedro A. Hernández, German Padilla, Dácil Nolasco, José Barrancos, Gladys Melían, Eleazar Padrón, Samara Dionis, David Calvo, Fátima Rodríguez, Kenji Notsu, Toshiya Mori, Minoru Kusakabe, M. Carmencita Arpa, Paolo Reniva and Martha Ibarra, Geology, v. 39 no. 3 p. 235-238, doi: 10.1130/G31586.1.

Global mean precipitation initially decreases

Changes in global-mean precipitation in response to warming, greenhouse gas forcing and black carbon – Frieler et al. (2011) “Precipitation changes are a key driver of climate change impacts. On average, global precipitation is expected to increase with warming. However, model projections show that precipitation does not scale linearly with surface air temperature. Instead, global hydrological sensitivity, the relative change of global-mean precipitation per degree of global warming, seems to vary across different scenarios and even with time. Based on output from 20 coupled Atmosphere-Ocean-General-Circulation-Models for up to 7 different scenarios, we discuss to what extent these variations can be explained by changes in the tropospheric energy budget. Our analysis supports earlier findings that long- and shortwave absorbers initially decrease global-mean precipitation. Including these absorbers into a multivariate scaling approach allows to closely reproduce the simulated global-mean precipitation changes. We find a sensitivity of global-mean precipitation to tropospheric greenhouse gas forcing of −0.42 ± 0.23%/(W/m2) (uncertainty given as one std of inter-model variability) and to black carbon emissions of −0.07 ± 0.02%/(Mt/yr). In combination with these two predictors the dominant longer-term effect of surface air temperatures on precipitation is estimated to be 2.2 ± 0.52%/K – much lower than the 6.5%/K that may be expected from the Clausius-Clapeyron relationship.” Frieler, K., M. Meinshausen, T. Schneider von Deimling, T. Andrews, and P. Forster (2011), Geophys. Res. Lett., 38, L04702, doi:10.1029/2010GL045953.

Sea level budget balanced by deep ocean heat

Deep ocean warming assessed from altimeters, Gravity Recovery and Climate Experiment, in situ measurements, and a non-Boussinesq ocean general circulation model – Song & Colberg (2011) “Observational surveys have shown significant oceanic bottom water warming, but they are too spatially and temporally sporadic to quantify the deep ocean contribution to the present-day sea level rise (SLR). In this study, altimetry sea surface height (SSH), Gravity Recovery and Climate Experiment (GRACE) ocean mass, and in situ upper ocean (0–700 m) steric height have been assessed for their seasonal variability and trend maps. It is shown that neither the global mean nor the regional trends of altimetry SLR can be explained by the upper ocean steric height plus the GRACE ocean mass. A non-Boussinesq ocean general circulation model (OGCM), allowing the sea level to rise as a direct response to the heat added into the ocean, is then used to diagnose the deep ocean steric height. Constrained by sea surface temperature data and the top of atmosphere (TOA) radiation measurements, the model reproduces the observed upper ocean heat content well. Combining the modeled deep ocean steric height with observational upper ocean data gives the full depth steric height. Adding a GRACE-estimated mass trend, the data-model combination explains not only the altimetry global mean SLR but also its regional trends fairly well. The deep ocean warming is mostly prevalent in the Atlantic and Indian oceans, and along the Antarctic Circumpolar Current, suggesting a strong relation to the oceanic circulation and dynamics. Its comparison with available bottom water measurements shows reasonably good agreement, indicating that deep ocean warming below 700 m might have contributed 1.1 mm/yr to the global mean SLR or one-third of the altimeter-observed rate of 3.11 ± 0.6 mm/yr over 1993–2008.” Song, Y. T., and F. Colberg (2011), J. Geophys. Res., 116, C02020, doi:10.1029/2010JC006601.

For those with good Finnish or Google translator skills, here’s my Finnish news article on this study. (Edited to add: Here’s English version of my news article.)

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2 Responses to “New research from last week 7/2011”

  1. [...] recent piece of research posted on Ari’s blog – AGW Observer – caught my attention: Rising temperatures caused by climatic warming may cause poleward [...]

  2. Watching the Deniers said

    Again thanks Ari, appreciate pointers to this research.

    Mike @ WtD

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