AGW Observer

Observations of anthropogenic global warming

New research from last week 49/2011

Posted by Ari Jokimäki on December 12, 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.

Pacific Decadal Oscillation might contribute to tropical belt widening

Effects of the PDO phase on the tropical belt width – Grassi et al. (2011) “Recent studies have shown that the Tropical Belt (TB) has progressively expanded since at least the late 1970’s. This trend has been largely attributed to the radiative forcing due to GHG increase and stratospheric ozone depletion, even if an influence of Sea Surface Temperature (SST) anomalies has been also suggested. In this work we investigate the impact of the Pacific Decadal Oscillation (PDO) on the TB width. The study is performed by using both AMIP (Atmospheric Model Intercomparison Project) and idealized simulations, produced by NCAR/CAM3 GCM, and reanalysis data (ERA-Interim, ERA-40 and MERRA). Reanalysis show that a switch of the PDO from a positive to a negative phase can lead to a significant TB expansion during the equinoxes. This effect, indicating a possible PDO contribution to the widening that characterized the TB width during the last decades, is not correctly reproduced by model simulations. Deficiencies in the sensitivity of model simulated convective processes to SST anomalies are suggested as a possible cause of the TB widening underestimation.” Barbara Grassi, Gianluca Redaelli, Pablo Osvaldo Canziani, and Guido Visconti, Journal of Climate 2011, doi:

Evaluating anthropogenic carbon and its effect to pH in South Pacific Ocean

Changes in South Pacific anthropogenic carbon – Waters et al. (2011) “The changes in anthropogenic CO2 are evaluated in the South Pacific, along the meridional line P18 (110°W) and the zonal line P06 (32°S), using the extended multiple linear regression (eMLR) method. The structure of the column inventory of anthropogenic CO2 on P18 is similar to the southern section of P16 in the central South Pacific (150°W), but the overall increase is greater by approximately 5–10 μmol kg−1. The value of the anthropogenic CO2 inventory on P18 is in agreement at the crossover point of an earlier evaluation of P06. Subsequent changes in pH due to the increase in anthropogenic CO2 are also evaluated. The change in pH is determined from the changes in anthropogenic CO2 and do not reflect variability in other decadal signals. For both cruise tracks, the average annual change in pH is −0.0016 mol kg−1 yr−1. This value is in good agreement with the average decrease in pH in the North Pacific, at the Hawaii Times Series and the subtropical North Atlantic. The uptake rates of anthropogenic CO2 are within reasonable agreement with similar studies in the South Pacific. There is evidence for greater uptake of anthropogenic CO2 in the western South Pacific and is attributed to the formation of subtropical Mode Water in the region.” Waters, J. F., F. J. Millero, and C. L. Sabine (2011), Global Biogeochem. Cycles, 25, GB4011, doi:10.1029/2010GB003988.

Nuclear power industry affects atmospheric radiocarbon concentration

Continental-scale enrichment of atmospheric 14CO2 from the nuclear power industry: potential impact on the estimation of fossil fuel-derived CO2 – Graven & Gruber (2011) “The 14C-free fossil carbon added to atmospheric CO2 by combustion dilutes the atmospheric 14C/C ratio (Δ14C), potentially providing a means to verify fossil CO2 emissions calculated using economic inventories. However, sources of 14C from nuclear power generation and spent fuel reprocessing can counteract this dilution and may bias 14C/C-based estimates of fossil fuel-derived CO2 if these nuclear influences are not correctly accounted for. Previous studies have examined nuclear influences on local scales, but the potential for continental-scale influences on Δ14C has not yet been explored. We estimate annual 14C emissions from each nuclear site in the world and conduct an Eulerian transport modeling study to investigate the continental-scale, steady-state gradients of Δ14C caused by nuclear activities and fossil fuel combustion. Over large regions of Europe, North America and East Asia, nuclear enrichment may offset at least 20% of the fossil fuel dilution in Δ14C, corresponding to potential biases of more than −0.25 ppm in the CO2 attributed to fossil fuel emissions, larger than the bias from plant and soil respiration in some areas. Model grid cells including high 14C-release reactors or fuel reprocessing sites showed much larger nuclear enrichment, despite the coarse model resolution of 1.8°×1.8°. The recent growth of nuclear 14C emissions increased the potential nuclear bias over 1985–2005, suggesting that changing nuclear activities may complicate the use of Δ14C observations to identify trends in fossil fuel emissions. The magnitude of the potential nuclear bias is largely independent of the choice of reference station in the context of continental-scale Eulerian transport and inversion studies, but could potentially be reduced by an appropriate choice of reference station in the context of local-scale assessments.” Graven, H. D. and Gruber, N., Atmos. Chem. Phys., 11, 12339-12349, doi:10.5194/acp-11-12339-2011, 2011. [Full text]

Human actions are seen in borehole temperatures in Czechia and Slovenia

Detection and quantification of local anthropogenic and regional climatic transient signals in temperature logs from Czechia and Slovenia – Dědeček et al. (2011) “The paper reports on detection and quantification of the impact of local anthropogenic structures and regional climatic changes on subsurface temperature field. The analyzed temperature records were obtained by temperature monitoring in a borehole in Prague-Spořilov (Czechia) and by repeated logging of a borehole in Šempeter (Slovenia). The observed data were compared with temperatures yielded by mathematical 3D time-variable geothermal models of the boreholes’ sites with the aim to decompose the observed transient component of the subsurface temperature into the part affected by construction of new buildings and other anthropogenic structures in surroundings of the boreholes and into the part affected by the ground surface temperature warming due to the surface air temperature rise. A direct human impact on the subsurface temperature warming was proved and contributions of individual anthropogenic structures to this change were evaluated. In the case of Spořilov, where the mean annual warming rate reached 0.034°C per year at the depth of 38.3 m during the period 1993–2008, it turned out that about half of the observed warming can be attributed to the air (ground) surface temperature change and half to the human activity on the surface in the immediate vicinity of the borehole. The situation is similar in Šempeter, where the effect of the recently built surface anthropogenic structures is detectable down to the depth of 80 m and the share of the anthropogenic signal on the non-stationary component of the observed subsurface temperature amounts to 30% at the depth of 50 m.” Petr Dědeček, Jan Šafanda and Dušan Rajver, Climatic Change, DOI: 10.1007/s10584-011-0373-5.

CO2 emissions matter to German car buyers

German car buyers’ willingness to pay to reduce CO2 emissions – Achtnicht (2011) “Motorized individual transport strongly contributes to global CO2 emissions, due to its intensive usage of fossil fuels. Current political efforts addressing this issue (i.e. emission performance standards in the EU) are directed towards car manufacturers. This paper focuses on the demand side. It examines whether CO2 emissions per kilometer is a relevant attribute in car choices. Based on a choice experiment among potential car buyers from Germany, a mixed logit specification is estimated. In addition, distributions of willingness-to-pay measures for an abatement of CO2 emissions are obtained. The results suggest that the emissions performance of a car matters substantially, but its consideration varies heavily across the sampled population. In particular, some evidence on gender, age and education effects on climate concerns is provided.” Martin Achtnicht, Climatic Change, DOI: 10.1007/s10584-011-0362-8.

Arctic Oscillation shows up in Swiss aquifers

Regime shift in groundwater temperature triggered by the Arctic Oscillation – Figura et al. (2011) “Groundwater is the world’s most important source of raw drinking water. However, the potential impact of climate change on this vital resource is unclear because of a lack of relevant long-term data. Here we statistically analyze over 20 years of groundwater temperature data from five Swiss aquifers fed predominantly by river-bank infiltration. The results reveal an abrupt increase in annual mean groundwater temperature centered on 1987–1988 that can also be observed in air and river temperatures. We associate this temperature increase with the Northern Hemisphere late 1980s climate regime shift (CRS), which itself is related to an abrupt change in the behavior of the Arctic Oscillation. Because temperature affects redox conditions in groundwater, groundwater biogeochemistry in aquifers fed by river-bank infiltration is likely to depend on large-scale climatic forcing and will be affected by climate change.” Figura, S., D. M. Livingstone, E. Hoehn, and R. Kipfer (2011), Geophys. Res. Lett., 38, L23401, doi:10.1029/2011GL049749.

Carbon dioxide emissions from global wind power deployment

Environmental implications of large-scale adoption of wind power: a scenario-based life cycle assessment – Arvesen & Hertwich (2011) “We investigate the potential environmental impacts of a large-scale adoption of wind power to meet up to 22% of the world’s growing electricity demand. The analysis builds on life cycle assessments of generic onshore and offshore wind farms, meant to represent average conditions for global deployment of wind power. We scale unit-based findings to estimate aggregated emissions of building, operating and decommissioning wind farms toward 2050, taking into account changes in the electricity mix in manufacturing. The energy scenarios investigated are the International Energy Agency’s BLUE scenarios. We estimate 1.7–2.6 Gt CO2-eq climate change, 2.1–3.2 Mt N-eq marine eutrophication, 9.2–14 Mt NMVOC photochemical oxidant formation, and 9.5–15 Mt SO2-eq terrestrial acidification impact category indicators due to global wind power in 2007–50. Assuming lifetimes 5 yr longer than reference, the total climate change indicator values are reduced by 8%. In the BLUE Map scenario, construction of new capacity contributes 64%, and repowering of existing capacity 38%, to total cumulative greenhouse gas emissions. The total emissions of wind electricity range between 4% and 14% of the direct emissions of the replaced fossil-fueled power plants. For all impact categories, the indirect emissions of displaced fossil power are larger than the total emissions caused by wind power.” Anders Arvesen and Edgar G Hertwich 2011 Environ. Res. Lett. 6 045102 doi:10.1088/1748-9326/6/4/045102. [Full text]

In low crop yield years biofuel production might emit more GHGs than fossil fuel burning

The significance of nitrous oxide emission due to cropping of grain for biofuel production: a Swedish perspective – Klemedtsson & Smith (2011) “The current regulations governing production of biofuels in the European Union require that they have to mitigate climate change, by producing >35% less greenhouse gases (GHG) than fossil fuels. There is a risk that this may not be achievable, since land use for crop production inevitably emits the potent GHG nitrous oxide (N2O), due to nitrogen fertilisation and cycling in the environment. We analyse first-generation biofuel production on agricultural land and conclude that efficient agricultural crop production resulting in a good harvest and low N2O emission can fulfil the EU standard, and is possible under certain conditions for the Swedish agricultural and bioethanol production systems. However, in years having low crop yields, and where cropping is on organic soils, total GHG emissions per unit of fuel produced can be even higher than those released by burning of fossil fuels. In general, the N2O emission size in Sweden and elsewhere in northern Europe is such that there is a >50% chance that the 35% saving requirement will not be met. Thus ecosystem N2O emissions have to be convincingly assessed. Here we compare Swedish emission data with values estimated by means of statistical models and by a global, top-down, approach; the measurements and the predictions often show higher values that would fail to meet the EU standard and thus prevent biofuel production development.” Kasimir Klemedtsson, Å. and Smith, K. A., Biogeosciences, 8, 3581-3591, doi:10.5194/bg-8-3581-2011, 2011. [Full text]

Attribution of climate change is not limited to model simulations

Patterns of change: whose fingerprint is seen in global warming? – Hegerl et al. (2011) “Attributing observed climate change to causes is challenging. This letter communicates the physical arguments used in attribution, and the statistical methods applied to explore to what extent different possible causes can be used to explain the recent climate records. The methods use fingerprints of climate change that are identified on the basis of the physics governing our climate system, and through the use of climate model experiments. These fingerprints characterize the geographical and vertical pattern of the expected changes caused by external influences, for example, greenhouse gas increases and changes in solar radiation, taking also into account how these forcings and their effects vary over time. These time–space fingerprints can be used to discriminate between observed climate changes caused by different external factors. Attribution assessments necessarily take the natural variability of the climate system into account as well, evaluating whether an observed change can be explained in terms of this internal variability alone, and estimating the contribution of this source of variability to the observed change. Hence the assessment that a large part of the observed recent warming is anthropogenic is based on a rigorous quantitative analysis of these joint drivers and their effects, and proceeds through a much more comprehensive and layered analysis than a comparison at face value of model simulations with observations.” Gabriele Hegerl et al 2011 Environ. Res. Lett. 6 044025 doi:10.1088/1748-9326/6/4/044025. [Full text]

Soil maximum freeze depth has decreased in Eurasian high latitudes

An observational 71-year history of seasonally frozen ground changes in the Eurasian high latitudes – Frauenfeld & Zhang (2011) “In recent decades, significant changes have occurred in high-latitude areas, particularly to the cryosphere. Sea ice extent and thickness have declined. In land areas, glaciers and ice sheets are experiencing negative mass balance changes, and there is substantial regional snow cover variability. Subsurface changes are also occurring in northern soils. This study focuses on these changes in the soil thermal regime, specifically the seasonally frozen ground region of Eurasia. We use a database of soil temperatures at 423 stations and estimate the maximum annual soil freezing depth at the 387 sites located on seasonally frozen ground. Evaluating seasonal freeze depth at these sites for 1930–2000 reveals a statistically significant trend of −4.5 cm/decade and a net change of −31.9 cm. Interdecadal variability is also evident such that there was no trend until the late 1960s, after which seasonal freeze depths decreased significantly until the early 1990s. From that point forward, likely through at least 2008, no change is evident. These changes in the soil thermal regime are most closely linked with the freezing index, but also mean annual air temperatures and snow depth. Antecedent conditions from the previous warm season do not appear to play a large role in affecting the subsequent cold season’s seasonal freeze depths. The strong decrease in seasonal freeze depths during the 1970s to 1990s was likely the result of strong atmospheric forcing from the North Atlantic Oscillation during that time period.” Oliver W Frauenfeld and Tingjun Zhang 2011 Environ. Res. Lett. 6 044024 doi:10.1088/1748-9326/6/4/044024. [Full text]

Analysis of tree-ring divergence problem

Who is the new sheriff in town regulating boreal forest growth? – Williams et al. (2011) Without abstract – here’s the first paragraph: “Climate change appears to be altering boreal forests. One recently observed symptom of these changes has been an apparent weakening of the positive relationship between high-latitude boreal tree growth and temperature at some sites (D’Arrigo et al 2008). This phenomenon is referred to as the ‘divergence problem’ or ‘divergence effect’ and is thought to reflect a non-linear relationship between temperature and tree growth, where recent warming has allowed other factors besides growing-season temperature to emerge as dominant regulators of annual growth rates.” A Park Williams et al 2011 Environ. Res. Lett. 6 041004 doi:10.1088/1748-9326/6/4/041004. [Full text available in the abstract page]

Climate change threatens turtle species

On the brink of extinction? How climate change may affect global Chelonian species richness and distribution – Ihlow et al. (2011) “Anthropogenic global climate change has already led to alterations in biodiversity patterns by directly and indirectly affecting species distributions. It has been suggested that poikilothermic animals, including reptiles, will be particularly affected by global change and large-scale reptile declines have already been observed. Currently, half of the world′s freshwater turtles and tortoises are considered threatened with extinction and climate change may exacerbate these declines. In this study, we assess how global chelonian species richness will change in the near future. We use species distribution models developed under current climate conditions for 78% of all extant species and project them onto different Intergovernmental Panel on Climate Change (IPCC) climate change scenarios for 2080. We detect a strong dependence of temperature shaping most species ranges, which coincide with their general temperature related physiological traits (i.e. temperature dependent sex determination). Furthermore, the extent and distribution of the current bioclimatic niches of most chelonians may change remarkably in the near future, likely leading to a substantial decrease of local species abundance and ultimately a reduction in species richness. Future climatic changes may cause the ranges of 86% of the species to contract and of these ranges nearly 12% are predicted to be situated completely outside their currently realized niches. Hence, the interplay of increasing habitat fragmentation and loss due to climatic stress may result in a serious threat for several chelonian species.” Flora Ihlow, Johannes Dambach, Jan O. Engler, Morris Flecks, Timo Hartmann, Sven Nekum, Hossein Rajaei, Dennis Rödder, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02623.x.

Study estimates 0.7% of global methane emissions comes from West Siberia mires

Regional methane emission from West Siberia mire landscapes – Glagolev et al. (2011) “Methane emissions from mires in all climate–vegetation zones of West Siberia (forest steppe, subtaiga, south taiga, middle taiga, north taiga, forest tundra and tundra) were measured using a static chamber method. The observed fluxes varied considerably from small negative values in forested bogs and palsa to hundreds of mgC m − 2 h − 1 in ponds and wet hollows. Observed data were consolidated in the form of the empirical model of methane emissions designated as the ‘standard model’. The model is based on medians of CH4 flux distributions of eight different micro-landscape types depending on their location and estimated duration of methane emission period within the climate–vegetation zone. The current version (Bc8) of the ‘standard model’ estimates methane flux from West Siberia mires at 2.93 ± 0.97 TgC CH4 yr − 1 that accounts for about 2.4% of the total methane emission from all mires or 0.7% of global methane emission from all sources.” M Glagolev et al 2011 Environ. Res. Lett. 6 045214 doi:10.1088/1748-9326/6/4/045214. [Full text]

Removing short term variability from global temperature analysis makes years 2009 and 2010 warmest

Global temperature evolution 1979–2010 – Foster & Rahmstorf (2011) “We analyze five prominent time series of global temperature (over land and ocean) for their common time interval since 1979: three surface temperature records (from NASA/GISS, NOAA/NCDC and HadCRU) and two lower-troposphere (LT) temperature records based on satellite microwave sensors (from RSS and UAH). All five series show consistent global warming trends ranging from 0.014 to 0.018 K yr−1. When the data are adjusted to remove the estimated impact of known factors on short-term temperature variations (El Niño/southern oscillation, volcanic aerosols and solar variability), the global warming signal becomes even more evident as noise is reduced. Lower-troposphere temperature responds more strongly to El Niño/southern oscillation and to volcanic forcing than surface temperature data. The adjusted data show warming at very similar rates to the unadjusted data, with smaller probable errors, and the warming rate is steady over the whole time interval. In all adjusted series, the two hottest years are 2009 and 2010.” Grant Foster and Stefan Rahmstorf 2011 Environ. Res. Lett. 6 044022 doi:10.1088/1748-9326/6/4/044022. [Full text]

Health costs of climate change in Europe are expected to be billions of euros

Projection of economic impacts of climate change in sectors of Europe based on bottom up analysis: human health – Watkiss & Hunt (2011) “This paper scopes a number of the health impacts of climate change in Europe (EU-27) quantitatively, using physical and monetary metrics. Temperature-related mortality effects, salmonellosis and coastal flooding-induced mental health impacts resulting from climate change are isolated from the effects of socio-economic change for the 2011–2040 and 2071–2100 time periods. The temperature-induced mortality effects of climate change include both positive and negative effects, for winter (cold) and summer (heat) effects, respectively, and have welfare costs (and benefits) of up to 100 billion Euro annually by the later time-period, though these are unevenly distributed across countries. The role of uncertainty in quantifying these effects is explored through sensitivity analysis on key parameters. This investigates climate model output, climate scenario, impact function, the existence and extent of acclimatisation, and the choice of physical and monetary metrics. While all of these lead to major differences in reported results, acclimatisation is particularly important in determining the size of the health impacts, and could influence the scale and form of public adaptation at the EU and national level. The welfare costs for salmonellosis from climate change are estimated at potentially several hundred million Euro annually by the period 2071–2100. Finally, a scoping assessment of the health costs of climate change from coastal flooding, focusing on mental health problems such as depression, are estimated at up to 1.5 billion Euro annually by the period 2071–2100.” Paul Watkiss and Alistair Hunt, Climatic Change, DOI: 10.1007/s10584-011-0342-z.

Global and Planetary Change is publishing a special issue on medieval climate

Climate in medieval time: How anomalous? – Diaz (2011) “The climate of the MWP/MCA has been a topic of scholarly research and debate for some 50 years (Diaz et al., in press). There is little doubt that sustained climatic anomalies on regional to hemispheric and global scales have had pronounced impacts on human society, and as events of the past few decades have shown, recent climatic extremes continue to affect humans regardless of their socioeconomic level. The publication of this special issue is meant to enhance the pool of knowledge about this period and hopefully contribute toward future advances.” Henry F. Diaz, Global and Planetary Change, doi:10.1016/j.gloplacha.2011.10.014.


One Response to “New research from last week 49/2011”

  1. “Who is the new sheriff in town regulating boreal forest growth?”

    Gotta love when scientists are given some leeway in their titles xD.

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