AGW Observer

Observations of anthropogenic global warming

New research from last week 22/2012

Posted by Ari Jokimäki on June 4, 2012

This week we have really cool collection of new papers. We have special section for papers on Greenland ice sheet – past, present, and future. Another special section deals with Arctic affairs – cryosphere, atmosphere, and biosphere. We also have other papers on diverse subjects, such as biomass burning, ENSO, Italian newspapers, Great Cormorants, black carbon, and diurnal temperature range.


GREENLAND ICE SHEET, THE PAST: What Greenland ice sheet melting did to North Atlantic climate during Last Interglacial?

Sensitivity of the North Atlantic climate to Greenland Ice Sheet melting during the Last Interglacial – Bakker et al. (2012) [FULL TEXT]

Abstract: “During the Last Interglacial (LIG; ~130 000 yr BP), part of the Greenland Ice Sheet (GIS) melted due to a warmer than present-day climate. However, the impact of this melting on the LIG climate in the North Atlantic region is relatively unknown. Using the LOVECLIM Earth system model of intermediate complexity, we have systematically tested the sensitivity of the LIG climate to increased freshwater runoff from the GIS. In addition, experiments have been performed to investigate the impact of an idealized reduction of both surface elevation and extent of the GIS on the LIG climate. Based on changes in the maximum sea-ice cover and the strength of the overturning circulation, three regimes have been identified, which are characterized by a specific pattern of surface temperature change in the North Atlantic region. By comparing the simulated deep ocean circulation with proxy-based reconstructions, the most realistic simulated climate could be discerned. The resulting climate is characterized by a shutdown of deep convection and a subsequent ~4 °C cooling in the Labrador Sea. Furthermore, a cooling of ~1 °C over the North Atlantic Ocean between 40° N and 70° N is seen. The prescribed reduction in surface elevation and extent of the GIS results in a local warming of up to 4 °C and amplifies the freshwater-forced reduction in deep convection and the resultant cooling in the Nordic Seas. A further comparison of simulated summer temperatures with both continental and oceanic proxy records reveals that the partial melting of the GIS during the LIG could have delayed maximum summer temperatures in the western part of the North Atlantic region relative to the insolation maximum.”

Citation: Bakker, P., Van Meerbeeck, C. J., and Renssen, H.: Sensitivity of the North Atlantic climate to Greenland Ice Sheet melting during the Last Interglacial, Clim. Past, 8, 995-1009, doi:10.5194/cp-8-995-2012, 2012.


GREENLAND ICE SHEET, THE PRESENT: Watching that Greenland ice flow

Ice flow in Greenland for the International Polar Year 2008–2009 – Rignot & Mouginot (2012)

Abstract: “A digital representation of ice surface velocity is essential for a variety of glaciological, geologic and geophysical analyses and modeling. Here, we present a new, reference, comprehensive, high-resolution, digital mosaic of ice motion in Greenland assembled from satellite radar interferometry data acquired during the International Polar Year 2008 to 2009 by the Envisat Advanced Synthetic-Aperture Radar (ASAR), the Advanced Land Observation System (ALOS)’s Phase-Array L-band SAR (PALSAR) and the RADARSAT-1 SAR that covers 99% of the ice sheet in area. The best mapping performance is obtained using ALOS PALSAR data due to higher levels of temporal coherence at the L-band frequency; but C-band frequency SAR data are less affected by the ionosphere. The ice motion map reveals various flow regimes, ranging from patterned enhanced flow into a few large glaciers in the cold, low precipitation areas of north Greenland; to diffuse, enhanced flow into numerous, narrow, fast-moving glaciers in the warmer, high precipitation sectors of northwest and southeast Greenland. We find that the 100 fastest glaciers (v > 800 m/yr) drain 66% of the ice sheet in area, marine-terminating glaciers drain 88% of Greenland, and basal-sliding motion dominates internal deformation over more than 50% of the ice sheet. This view of ice sheet motion provides significant new constraints on ice flow modeling.”

Citation: Rignot, E. and J. Mouginot (2012), Ice flow in Greenland for the International Polar Year 2008–2009, Geophys. Res. Lett., 39, L11501, doi:10.1029/2012GL051634.


GREENLAND ICE SHEET, THE FUTURE: Uncertainties in projecting Greenland ice sheet future melting

An assessment of key model parametric uncertainties in projections of Greenland Ice Sheet behavior – Applegate et al. (2012) [FULL TEXT]

Abstract: “Lack of knowledge about the values of ice sheet model input parameters introduces substantial uncertainty into projections of Greenland Ice Sheet contributions to future sea level rise. Computer models of ice sheet behavior provide one of several means of estimating future sea level rise due to mass loss from ice sheets. Such models have many input parameters whose values are not well known. Recent studies have investigated the effects of these parameters on model output, but the range of potential future sea level increases due to model parametric uncertainty has not been characterized. Here, we demonstrate that this range is large, using a 100-member perturbed-physics ensemble with the SICOPOLIS ice sheet model. Each model run is spun up over 125 000 yr using geological forcings and subsequently driven into the future using an asymptotically increasing air temperature anomaly curve. All modeled ice sheets lose mass after 2005 AD. Parameters controlling surface melt dominate the model response to temperature change. After culling the ensemble to include only members that give reasonable ice volumes in 2005 AD, the range of projected sea level rise values in 2100 AD is ~40 % or more of the median. Data on past ice sheet behavior can help reduce this uncertainty, but none of our ensemble members produces a reasonable ice volume change during the mid-Holocene, relative to the present. This problem suggests that the model’s exponential relation between temperature and precipitation does not hold during the Holocene, or that the central-Greenland temperature forcing curve used to drive the model is not representative of conditions around the ice margin at this time (among other possibilities). Our simulations also lack certain observed physical processes that may tend to enhance the real ice sheet’s response. Regardless, this work has implications for other studies that use ice sheet models to project or hindcast the behavior of the Greenland Ice Sheet.”

Citation: Applegate, P. J., Kirchner, N., Stone, E. J., Keller, K., and Greve, R.: An assessment of key model parametric uncertainties in projections of Greenland Ice Sheet behavior, The Cryosphere, 6, 589-606, doi:10.5194/tc-6-589-2012, 2012.


Changes in diurnal temperature range in United States since 1901

U.S. Diurnal Temperature Range Variability and Regional Causal Mechanisms, 1901-2002 – Lauritsen & Rogers (2012)

Abstract: “Long-term (1901-2002) diurnal air temperature range data (DTR) are evaluated to examine its spatial and temporal variability across the United States, the early-century origin of the DTR declines, and the relative regional contributions to DTR variability among cloud cover, precipitation, soil moisture and atmosphere/ocean teleconnections. Rotated principal component analysis (RPCA) of the Climate Research Unit (CRU) TS 2.1 dataset identifies 5 regions of unique spatial U.S. DTR variability. RPCA creates regional orthogonal indices of cloud cover, soil moisture, precipitation and the teleconnections used subsequently in stepwise multiple linear regression to examine their regional impact on DTR, maximum (Tmax), and minimum (Tmin) temperatures. The southwestern U.S. has the smallest DTR and cloud cover trends as both Tmax and Tmin increase over the century. Tmin increases are the primary influence on DTR trend in other regions except in the south central U.S. where downward Tmax trend largely affects its DTR decline. Tmax and DTR tend to both exhibit simultaneous decadal variations during unusually wet and dry periods in response to cloud cover, soil moisture, and precipitation variability. The widely-reported post-1950 DTR decline began regionally at various times ranging from around 1910 to the 1950s. Cloud cover alone accounts for up to 63.2% of regional annual DTR variability, with cloud cover trends driving DTR in northern states. Cloud cover, soil moisture, precipitation, and atmospheric/oceanic teleconnection indices account for up to 80.0% of regional variance over 1901-2002 (75.4% in detrended data) although the latter only account for small portions of this variability.”

Citation: Ryan G. Lauritsen and Jeffrey C. Rogers, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00429.1.


The increase of anthropogenic black carbon emissions in China since 1980

Spatial and temporal variation of anthropogenic black carbon emissions in China for the period 1980–2009 – Qin & Xie (2012) [FULL TEXT]

Abstract: “Multi-year inventories of anthropogenic black carbon emissions, including both fuel consumption and biomass open burning, at a high spatial resolution of 0.25°×0.25° have been constructed in China using GIS methodology for the period 1980–2009, based on official statistical data and time-varying emission factors. Results show that black carbon emissions increased from 0.87 Tg in 1980 to 1.88 Tg in 2009 with a peak in about 1995, and had been continually increasing in the first decade of the 21 century. Residential contribution to the total BC emissions declined from 82.03% in 1980 to 42.33% in 2009 at a continuous diminishing trend, but had always been the dominant contributor in China. While contributions from industry and transportation sectors had increased notably. BC emissions were mainly concentrated in the central eastern districts, the three northeastern provinces and the Sichuan Basin, covering 22.30% of China’s territory, but were responsible for 43.02%, 50.47%, 50.69% and 54.30% of the national black carbon emissions in 1985, 1995, 2005 and 2009, respectively. Besides, China made up 70%–85% of BC emissions in East Asia, half of the emissions in Asia, and accounted for averagely 18.97% of the global BC emissions during the estimation period.”

Citation: Qin, Y. and Xie, S. D.: Spatial and temporal variation of anthropogenic black carbon emissions in China for the period 1980–2009, Atmos. Chem. Phys., 12, 4825-4841, doi:10.5194/acp-12-4825-2012, 2012.


Colony of Great Cormorants emits nitrous oxide

The Great Cormorant (Phalacrocorax carbo) colony as a “hot spot” of nitrous oxide (N2O) emission in central Japan – Mizota et al. (2012)

Abstract: “Unusual high soil fluxes up to ca. 500 mg N2O m−2 h−1 emission were associated with a continued breeding/roosting colony of Great Cormorant in central Japan. This flux is nearly two-orders of magnitude higher than those hitherto documented. The flux was markedly dependent upon the soil surface temperature, i.e., higher in April–October during the prevailing high air temperatures, as compared with November to March. Integrated input of fecal N at rearing and fledging stages of chicks followed by coupled mineralization, nitrification and subsequently denitrification processes under humid and temperate regimes is responsible for such an unusual flux. The Great Cormorant colony serves as a “hot spot” of N2O emission of natural origin.”

Citation: Chitoshi Mizota, Kosuke Noborio, Yoshiaki Mori, Atmospheric Environment, Volume 57, September 2012, Pages 29–34, http://dx.doi.org/10.1016/j.atmosenv.2012.02.007.


Study reveals the climate change agendas of Italian newspapers

How do the media affect public perception of climate change and geohazards? An Italian case study – Pasquaré & Oppizzi (2012)

Abstract: “This paper uses a combination of a qualitative approach and a quantitative, software-based approach to explore the Italian print media construction of climate change and geohazards between 2007 and 2010. We have broken down our analysis in two sections: the first one deals with the coverage of climate change; the second one focuses on the media representation of hydrogeological hazards and extreme events in Italy. Our software-based, qualitative and quantitative analysis of 1253 storylines from two major Italian broadsheets (the La Repubblica and the Corriere della Sera) has enabled us to assess the presence of typical journalistic frames such as conflict and dramatization, as well as newly-introduced ones such as “prevention vs damages”, and “weather vs climate”. Our results show that the two newspapers appear to have different “agendas” that might have different impacts on their own readerships: the La Repubblica has been on the forefront of forging a broad public consensus on the need for actions aimed at tackling climate change, whereas the Corriere della Sera has gradually built a journalistic agenda aimed at minimizing the urgency of the climate change problem. As regards the media’s representation of hydrogeological hazards, we have confirmed what assessed by previous research, i.e. that Italian journalists still prefer to focus on damages rather than prevention; on a better note, the tendency of the Italian press to confuse weather with climate, blaming climate change for extreme rainfalls causing landslides and floods, has decreased in the last four years.”

Citation: Federico A. Pasquaré, Paolo Oppizzi, Global and Planetary Change, Volumes 90–91, June 2012, Pages 152–157, http://dx.doi.org/10.1016/j.gloplacha.2011.05.010.


ENSO makes it difficult to detect anthropogenic trend in eastern Tropical Pacific

The Effect of ENSO Events on the Tropical Pacific Mean Climate: Insights from an Analytical Model – Liang et al. (2012)

Abstract: “To better understand the causes of climate change in the tropical Pacific on the decadal and longer time scales, we delineate the rectification effect of ENSO events into the mean state by contrasting the time-mean state of a low-order model for the Pacific with its equilibrium state. The model encapsulates the essential physics of the ENSO system, but remains simple enough to allow us to obtain its equilibrium state. The model has an oscillatory regime that resembles the observations. In this oscillatory regime, the time-mean SST in the eastern equatorial Pacific is found to be significantly different from the corresponding equilibrium SST, with the former being warmer than the latter. The difference is found to be proportional to the amplitude of ENSO. In addition, the zonal SST contrast of the time-mean state is found to be less sensitive to increases in external forcing than that of the equilibrium state, due to warming effect of ENSO events on the eastern Pacific. It is further shown this rectification effect of ENSO events owns to the nonlinear advection term in the heat budget equation. The study elucidates the role of ENSO events in shaping the tropical mean climate state and suggests that decadal warming in the recent decades in the eastern tropical Pacific may be more a consequence than a cause of the elevated ENSO activity during the same period. The results also provide a simple explanation for why it is difficult to detect an anthropogenically forced trend in the zonal SST contrast in the observations.”

Citation: Jin Liang, Xiu-Qun Yang, and De-Zheng Sun, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00490.1.


Anthropogenic activities have altered natural trends in biomass burning from about 5500 years ago

Trends in biomass burning in the Carpathian region over the last 15,000 years – Feurdean et al. (2012)

Abstract: “Fire is recognized as a critical process with significant impacts on biota and the atmosphere. In this study, 11 micro- and macrocharcoal sedimentary records extracted from peat bogs and lakes at different elevations in the Carpathian region (in Hungary and Romania) were used to explore the patterns and the potential underlying mechanisms in biomass burning in this region during the last 15,000 years. Results from micro-charcoal and macro-charcoal data show similar trends in biomass burning and suggest that the major signal of both charcoal size-fragments relates mainly to local fires. Fire activity was low during the lateglacial, attained maximum values in the early Holocene (11,700–8000 cal. yr BP), become lower than present during the mid-late Holocene (8000–1000 cal yr BP), and increased again over the last 1000 years. The reconstructed spatial trends in biomass burning display different degrees of heterogeneity through time. Generally, there was more spatial similarity in fire activity across the study region during the lateglacial and early Holocene (15,000–8000 cal yr BP), followed by increased spatial heterogeneity from ca 8000 cal yr BP onwards. Biomass burning appears to have been primarily modulated by climate during both the lateglacial and Holocene, through its effect on vegetation productivity and therefore fuel availability (lateglacial), and fuel structure, moisture and flammability (the Holocene). Onsite human activities are likely to have provided an extra ignition source already in the early Holocene. However, evidence suggest that anthropogenic activities have markedly altered the natural trends in biomass burning from about 5500 yr BP (lowlands) and over the last 2000-1000 years (in the mountain environments), by either removing the biomass (in the lowlands) or igniting fire where it seldom occurs naturally (i.e., in the mountain environments). On the other hand, burning activity also appears coincident with significant changes in tree species compositions, indicating that fire has likely acted as a driving factor in forest dynamics. Results also suggest that peat deposits provide a more localized fire record than lakes, and that trends and patterns of change can be different even for sites situated close to each other.”

Citation: Angelica Feurdeana, Allan Spessa, Enikö K. Magyari, Katherine J. Willis, Daniel Veres, Thomas Hickler, Quaternary Science Reviews, Volume 45, 29 June 2012, Pages 111–125.


ARCTIC AFFAIRS, CRYOSPHERE: How long has mountain permafrost existed continuously in Norway?

The relative age of mountain permafrost – estimation of Holocene permafrost limits in Norway – Lilleøren et al. (2012)

Abstract: “For Scandinavia in general and Norway in particular the regional distribution of mountain permafrost is reasonably well known, both through ground temperature measurements in boreholes, geophysical soundings and spatial modeling. However, the evolution of permafrost over longer time periods, such as the Holocene, is unknown, but is considered to have significance for landscape development and geomorphological processes in high mountain areas of Scandinavia. In this study two mean annual air temperature series covering the Holocene have been compiled to drive a 1D heat flow model over a 10 kyr period for several sites in Norway. At each site temperature-monitored boreholes exist, which were used to calibrate the model. In addition the spatial distribution of permafrost during selected time periods of the Holocene was addressed using a newly implemented version of an equilibrium permafrost model. The result of this study indicates an altitudinal zonation of relative permafrost age in Norway. We find that permafrost has existed continuously since the deglaciation at the highest altitudes, whereas in large areas where permafrost currently is present, it degraded during the Holocene thermal maximum (HTM). In all boreholes the coldest simulated permafrost occurred during the ‘Little Ice Age’ (LIA), and also the largest areal distribution of Holocene permafrost in Norway seems to be connected to the LIA.”

Citation: Karianne S. Lilleøren, Bernd Etzelmüller, Kjersti Gisnås, Thomas V. Schuler, Ole Humlum, Global and Planetary Change, http://dx.doi.org/10.1016/j.gloplacha.2012.05.016.


ARCTIC AFFAIRS, CRYOSPHERE & ATMOSPHERE: Arctic sea ice retreats, clouds go higher

The Impact of Arctic sea-ice retreat on the recent change in cloud-base height during autumn – Sato et al. (2012)

Abstract: “Cloud-base observations over the ice-free Chukchi and Beaufort Seas in autumn were conducted using a shipboard ceilometer and radiosondes during the 1999–2010 cruises of the Japanese R/V Mirai. In comparison with cloud-base heights in an ice-covered case (the Surface Heat Budget of the Arctic Ocean project in 1998), our ice-free results showed a 30% decrease (increase) in the frequency of low clouds with a ceiling below (above) 500 m. Temperature profiles revealed that the boundary layer was well developed over the ice-free ocean in the 2000s, whereas a stable layer dominated during the ice-covered period in 1998. The change in surface boundary conditions likely resulted in the difference in cloud-base height, although it had little impact on air temperatures in the mid- and upper troposphere. Data from the 2010 R/V Mirai cruise were investigated in detail in terms of air-sea temperature difference. Stratus clouds near the sea surface were predominant under a warm advection situation, whereas stratocumulus clouds with a cloud-free layer were significant under a cold advection situation. The threshold temperature difference between sea surface and air temperatures for distinguishing the dominant cloud types was 3 K. Anomalous upward turbulent heat fluxes associated with the sea-ice retreat have likely contributed to warming of the lower troposphere.”

Citation: Sato, K., J. Inoue, Y.-M. Kodama, and J. E. Overland (2012), Impact of Arctic sea-ice retreat on the recent change in cloud-base height during autumn, Geophys. Res. Lett., 39, L10503, doi:10.1029/2012GL051850.


ARCTIC AFFAIRS, ATMOSPHERE: Factors contributing to Arctic warming

Local and remote controls on observed Arctic warming – Screen et al. (2012)

Abstract: “The Arctic is warming two to four times faster than the global average. Debate continues on the relative roles of local factors, such as sea ice reductions, versus remote factors in driving, or amplifying, Arctic warming. This study examines the vertical profile and seasonality of observed tropospheric warming, and addresses its causes using atmospheric general circulation model simulations. The simulations enable the isolation and quantification of the role of three controlling factors of Arctic warming: 1) observed Arctic sea ice concentration (SIC) and sea surface temperature (SST) changes; 2) observed remote SST changes; and 3) direct radiative forcing (DRF) due to observed changes in greenhouse gases, ozone, aerosols, and solar output. Local SIC and SST changes explain a large portion of the observed Arctic near-surface warming, whereas remote SST changes explain the majority of observed warming aloft. DRF has primarily contributed to Arctic tropospheric warming in summer.”

Citation: Screen, J. A., C. Deser, and I. Simmonds (2012), Local and remote controls on observed Arctic warming, Geophys. Res. Lett., 39, L10709, doi:10.1029/2012GL051598.


ARCTIC AFFAIRS, BIOSPHERE: Review of evidence on climate and sea ice effects to polar bears

Effects of Climate Warming on Polar Bears: A Review of the Evidence – Stirling & Derocher (2012)

Abstract: “Climate warming is causing unidirectional changes to annual patterns of sea ice distribution, structure, and freeze-up. We summarize evidence that documents how loss of sea ice, the primary habitat of polar bears (Ursus maritimus), negatively affects their long-term survival. To maintain viable subpopulations, polar bears depend upon sea ice as a platform from which to hunt seals for long enough each year to accumulate sufficient energy (fat) to survive periods when seals are unavailable. Less time to access to prey, because of progressively earlier breakup in spring, when newly-weaned ringed seal (Pusa hispida) young are available, results in longer periods of fasting, lower body condition, decreased access to denning areas, fewer and smaller cubs, lower survival of cubs as well as bears of other age classes and, finally, subpopulation decline toward eventual extirpation. The chronology of climate-driven changes will vary between subpopulations, with quantifiable negative effects being documented first in the more southerly subpopulations, such as those in Hudson Bay or the southern Beaufort Sea. As the bears’ body condition declines, more seek alternate food resources so the frequency of conflicts between bears and humans increases. In the most northerly areas, thick multiyear ice, through which little light penetrates to stimulate biological growth on the underside, will be replaced by annual ice which facilitates greater productivity and may create habitat more favorable to polar bears over continental shelf areas in the short term. If the climate continues to warm and eliminate sea ice as predicted, polar bears will largely disappear from the southern portions of their range by mid-century. They may persist in the northern Canadian Arctic Islands and northern Greenland for the foreseeable future, but their long-term viability, with a much reduced global population size in a remnant of their former range, is uncertain.”

Citation: Ian Stirling, Andrew E. Derocher, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02753.x.


CLASSIC OF THE WEEK: Barrell (1908)

Relations between Climate and Terrestrial Deposits – Barrell (1908) [FULL TEXT]

Abstract: No abstract.

Citation: Joseph Barrell, The Journal of Geology, Vol. 16, No. 2 (Feb. – Mar., 1908) (pp. 159-190).


When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

2 Responses to “New research from last week 22/2012”

  1. mosi said

    Why is this one out?

    http://www.nature.com/ngeo/journal/v5/n6/full/ngeo1481.html

    It made some fuss in the media.

  2. Ari Jokimäki said

    I rarely include anything from Nature just because those usually make fuss in the media anyway. My weekly posts on new research are usually such, that most of them do not get publicity elsewhere. You can think of my posts as supplementary to other news services.

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