AGW Observer

Observations of anthropogenic global warming

New research from last week 24/2011

Posted by Ari Jokimäki on June 20, 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:

Different retreat rates of Greenland outlet glaciers

Mass balance of Greenland’s three largest outlet glaciers, 2000–2010 – Howat et al. (2011) “Acceleration of Greenland’s three largest outlet glaciers, Helheim, Kangerdlugssuaq and Jakobshavn Isbræ, accounted for a substantial portion of the ice sheet’s mass loss over the past decade. Rapid changes in their discharge, however, make their cumulative mass-change uncertain. We derive monthly mass balance rates and cumulative balance from discharge and surface mass balance (SMB) rates for these glaciers from 2000 through 2010. Despite the dramatic changes observed at Helheim, the glacier gained mass over the period, due primarily to the short-duration of acceleration and a likely longer-term positive balance. In contrast, Jakobshavn Isbræ lost an equivalent of over 11 times the average annual SMB and loss continues to accelerate. Kangerdlugssuaq lost over 7 times its annual average SMB, but loss has returned to the 2000 rate. These differences point to contrasts in the long-term evolution of these glaciers and the danger in basing predictions on extrapolations of recent changes.” Howat, I. M., Y. Ahn, I. Joughin, M. R. van den Broeke, J. T. M. Lenaerts, and B. Smith (2011), Geophys. Res. Lett., 38, L12501, doi:10.1029/2011GL047565. [Full text]

Future changes in GHG global warming potentials

Future changes in global warming potentials under representative concentration pathways – Reisinger et al. (2011) “Global warming potentials (GWPs) are the metrics currently used to compare emissions of different greenhouse gases under the United Nations Framework Convention on Climate Change. Future changes in greenhouse gas concentrations will alter GWPs because the radiative efficiencies of marginal changes in CO2, CH4 and N2O depend on their background concentrations, the removal of CO2 is influenced by climate–carbon cycle feedbacks, and atmospheric residence times of CH4 and N2O also depend on ambient temperature and other environmental changes. We calculated the currently foreseeable future changes in the absolute GWP of CO2, which acts as the denominator for the calculation of all GWPs, and specifically the GWPs of CH4 and N2O, along four representative concentration pathways (RCPs) up to the year 2100. We find that the absolute GWP of CO2 decreases under all RCPs, although for longer time horizons this decrease is smaller than for short time horizons due to increased climate–carbon cycle feedbacks. The 100-year GWP of CH4 would increase up to 20% under the lowest RCP by 2100 but would decrease by up to 10% by mid-century under the highest RCP. The 100-year GWP of N2O would increase by more than 30% by 2100 under the highest RCP but would vary by less than 10% under other scenarios. These changes are not negligible but are mostly smaller than the changes that would result from choosing a different time horizon for GWPs, or from choosing altogether different metrics for comparing greenhouse gas emissions, such as global temperature change potentials.” Andy Reisinger, Malte Meinshausen and Martin Manning, Environ. Res. Lett. 6 024020 doi: 10.1088/1748-9326/6/2/024020. [Full text]

Review of stratospheric temperature trends

Stratospheric temperature trends: our evolving understanding – Seidel et al. (2011) “We review the scientific literature since the 1960s to examine the evolution of modeling tools and observations that have advanced understanding of global stratospheric temperature changes. Observations show overall cooling of the stratosphere during the period for which they are available (since the late 1950s and late 1970s from radiosondes and satellites, respectively), interrupted by episodes of warming associated with volcanic eruptions, and superimposed on variations associated with the solar cycle. There has been little global mean temperature change since about 1995. The temporal and vertical structure of these variations are reasonably well explained by models that include changes in greenhouse gases, ozone, volcanic aerosols, and solar output, although there are significant uncertainties in the temperature observations and regarding the nature and influence of past changes in stratospheric water vapor. As a companion to a recent WIREs review of tropospheric temperature trends, this article identifies areas of commonality and contrast between the tropospheric and stratospheric trend literature. For example, the increased attention over time to radiosonde and satellite data quality has contributed to better characterization of uncertainty in observed trends both in the troposphere and in the lower stratosphere, and has highlighted the relative deficiency of attention to observations in the middle and upper stratosphere. In contrast to the relatively unchanging expectations of surface and tropospheric warming primarily induced by greenhouse gas increases, stratospheric temperature change expectations have arisen from experiments with a wider variety of model types, showing more complex trend patterns associated with a greater diversity of forcing agents.” Dian J. Seidel, Nathan P. Gillett, John R. Lanzante, Keith P. Shine, Peter W. Thorne, Wiley Interdisciplinary Reviews: Climate Change, DOI: 10.1002/wcc.125.

Evidence for ice shelf break-up in the past in Antarctica

Geological record of ice shelf break-up and grounding line retreat, Pine Island Bay, West Antarctica – Jakobsson et al. (2011) “The catastrophic break-ups of the floating Larsen A and B ice shelves (Antarctica) in 1995 and 2002 and associated acceleration of glaciers that flowed into these ice shelves were among the most dramatic glaciological events observed in historical time. This raises a question about the larger West Antarctic ice shelves. Do these shelves, with their much greater glacial discharge, have a history of collapse? Here we describe features from the seafloor in Pine Island Bay, West Antarctica, which we interpret as having been formed during a massive ice shelf break-up and associated grounding line retreat. This evidence exists in the form of seafloor landforms that we argue were produced daily as a consequence of tidally influenced motion of mega-icebergs maintained upright in an iceberg armada produced from the disintegrating ice shelf and retreating grounding line. The break-up occurred prior to ca. 12 ka and was likely a response to rapid sea-level rise or ocean warming at that time.” Martin Jakobsson, John B. Anderson, Frank O. Nitsche, Julian A. Dowdeswell, Richard Gyllencreutz, Nina Kirchner, Rezwan Mohammad, Matthew O’Regan, Richard B. Alley, Sridhar Anandakrishnan, Björn Eriksson, Alexandra Kirshner, Rodrigo Fernandez, Travis Stolldorf, Rebecca Minzoni and Wojciech Majewski, Geology, v. 39 no. 7 p. 691-694, doi: 10.1130/G32153.1.

Measuring atmospheric water vapor with cheap IR thermometer

Measuring Total Column Water Vapor by Pointing an Infrared Thermometer at the Sky – Mims et al. (2011) “A 2-year study affirms that the temperature indicated by an inexpensive ($20 to $60) IR thermometer pointed at the cloud-free zenith sky (Tz) is a proxy for total column water vapor (precipitable water or PW). Tz was measured at or near solar noon, and occasionally at night, from 8 September 2008 to 18 October 2010 at a field in South-Central Texas. PW was measured by a MICROTOPS II sun photometer. The coefficient of correlation (r2) of PW and Tz was 0.90, and the rms difference was 3.2 mm. A comparison of Tz with PW from a GPS site 31 km NNE yielded an r2 of 0.79, and an rms difference of 5.8 mm. An expanded study compared Tz from eight IR thermometers with PW at various times during the day and night from 17 May to 18 October 2010, mainly at the Texas site and 10 days at Hawaii’s Mauna Loa Observatory. The best results were provided by two IR thermometers that yielded an r2 of 0.96 and an rms difference with PW of 2.7 mm. The results of both the ongoing 2-year study and the 5-month comparison show that IR thermometers can measure PW with an accuracy (rms difference/mean PW) approaching 10%, the accuracy typically ascribed to sun photometers. The simpler IR method, which works day and night, can be easily mastered by students, amateur scientists and cooperative weather observers.” Forrest M. Mims III, Lin Hartung Chambers, David R. Brooks, Bulletin of the American Meteorological Society 2011. [Full text]

Growing frost flowers in the lab

Frost flowers in the laboratory: Growth, characteristics, aerosol, and the underlying sea ice – Roscoe et al. (2011) “In the laboratory, we have investigated the growth and composition of frost flowers. Their ionic composition has shown little difference from those of field measurements. Young frost flowers grown on sea ice are saline, leading us to speculate that wicking occurs continually during their growth on sea ice. The surface area of frost flowers is only a little larger than the area of ice underneath, consistent with recent field measurements from the Arctic. Time-lapse photography has allowed us to observe the extreme mobility of freshly forming sea ice, at the stage at which the mush has become rather solid, and continuing while the flowers grow. This mobility results in new brine being expelled to the surface, which therefore remains wet. During various stages of frost flower growth, we observed their freshly formed dendritic parts rapidly diminishing in size after contacting the surface, consistent with repeated wicking. Frost flowers proved to be very stable in the presence of wind, such that no aerosol was observed when wind was blown across them in the laboratory chamber. This is consistent with recent field observations of frost flowers coexisting with wind-blown snow.” Roscoe, H. K., B. Brooks, A. V. Jackson, M. H. Smith, S. J. Walker, R. W. Obbard, and E. W. Wolff (2011), J. Geophys. Res., 116, D12301, doi:10.1029/2010JD015144.

Anaerobic oxidation prevents methane outgassing from Lake Tanganyika

What prevents outgassing of methane to the atmosphere in Lake Tanganyika? – Durisch-Kaiser et al. (2011) “Tropical East African Lake Tanganyika hosts the Earth’s largest anoxic freshwater body. The entire water column holds over 23 Tg of the potent greenhouse gas methane (CH4). Methane is formed under sulphate-poor conditions via carbon dioxide reduction or fermentation from detritus and relict sediment organic matter. Permanent density stratification supports an accumulation of CH4 below the permanent oxycline. Despite CH4 significance for global climate, anaerobic microbial consumption of CH4 in freshwater is poorly understood. Here we provide evidence for intense methanotrophic activity not only in the oxic but also in the anoxic part of the water column of Lake Tanganyika. We measured CH4, 13C of dissolved CH4, dissolved oxygen (O2), sulphate (SO42-), sulphide (HS-) and the transient tracers chlorofluorocarbon-12 (CFC-12) and tritium (3H). A basic one-dimensional model, which considers vertical transport and biogeochemical fluxes and transformations, was used to interpret the vertical distribution of these substances. The results suggest that the anaerobic oxidation of CH4 is an important mechanism limiting CH4 to the anoxic zone of Lake Tanganyika. The important role of the anaerobic oxidation for CH4 concentrations is further supported by high abundances (up to ∼33% of total DAPI-stained cells) of single living archaea, identified by fluorescence in situ hybridization.” Durisch-Kaiser, E., M. Schmid, F. Peeters, R. Kipfer, C. Dinkel, T. Diem, C. J. Schubert, and B. Wehrli (2011), J. Geophys. Res., 116, G02022, doi:10.1029/2010JG001323.

What takes volcanoes a whole year mankind does in just a few days

Human Activities Emit Way More Carbon Dioxide Than Do Volcanoes – AGU news article “On average, human activities put out in just three to five days the equivalent amount of carbon dioxide that volcanoes produce globally each year. So concludes a scientist who reviewed five published studies of present-day global volcanic carbon dioxide emissions and compared those emissions to anthropogenic (human-induced) carbon dioxide output.” AGU Release No. 11–22, 14 June 2011.

Europe cold winter 2009-2010: extreme NAO but relatively warm

European cold winter 2009–2010: How unusual in the instrumental record and how reproducible in the ARPEGE-Climat model? – Ouzeau et al. (2011) “Boreal winter 2009–2010 made headlines for cold anomalies in many countries of the northern mid-latitudes. Northern Europe was severely hit by this harsh winter in line with a record persistence of the negative phase of the North Atlantic Oscillation (NAO). In the present study, we first provide a wider perspective on how unusual this winter was by using the recent 20th Century Reanalysis. A weather regime analysis shows that the frequency of the negative NAO was unprecedented since winter 1939–1940, which is then used as a dynamical analog of winter 2009–2010 to demonstrate that the latter might have been much colder without the background global warming observed during the twentieth century. We then use an original nudging technique in ensembles of global atmospheric simulations driven by observed sea surface temperature (SST) and radiative forcings to highlight the relevance of the stratosphere for understanding if not predicting such anomalous winter seasons. Our results demonstrate that an improved representation of the lower stratosphere is necessary to reproduce not only the seasonal mean negative NAO signal, but also its intraseasonal distribution and the corresponding increased probability of cold waves over northern Europe.” Ouzeau, G., J. Cattiaux, H. Douville, A. Ribes, and D. Saint-Martin (2011), Geophys. Res. Lett., 38, L11706, doi:10.1029/2011GL047667.

Climate change causes concrete to deteriorate more rapidly

Impact of climate change on corrosion and damage to concrete infrastructure in Australia – Wang et al. (2011) “The durability of concrete is determined largely by its deterioration over time which is affected by the environment. Climate change may alter this environment, causing an acceleration of deterioration processes that will affect the safety and serviceability of concrete infrastructure in Australia, U.S., Europe, China and elsewhere. This investigation of concrete deterioration under changing climate in Australia uses Monte-Carlo simulation of results from General Circulation Models (GCMs) and considers high greenhouse gas emission scenarios representing the A1FI schemes of the IPCC. We present the implications of climate change for the durability of concrete structures, in terms of changes in probability of reinforcement corrosion initiation and corrosion induced damage at a given calendar year between 2000 and 2100 across Australia. Since the main driver to increased concrete deterioration is CO2 concentration and temperature, then increases in damage risks observed in Australia are likely to be observed in other concrete infrastructure internationally. The impact of climate change on the deterioration cannot be ignored, but can be addressed by new approaches in design. Existing concrete structures, for which design has not considered the effects of changing climate may deteriorate more rapidly than originally planned.” Xiaoming Wang, Mark G. Stewart and Minh Nguyen, Climatic Change, DOI: 10.1007/s10584-011-0124-7.

Summer snowfall decreases in Arctic because it changes to rain

Declining summer snowfall in the Arctic: causes, impacts and feedbacks – Screen & Simmonds (2011) “Recent changes in the Arctic hydrological cycle are explored using in situ observations and an improved atmospheric reanalysis data set, ERA-Interim. We document a pronounced decline in summer snowfall over the Arctic Ocean and Canadian Archipelago. The snowfall decline is diagnosed as being almost entirely caused by changes in precipitation form (snow turning to rain) with very little influence of decreases in total precipitation. The proportion of precipitation falling as snow has decreased as a result of lower-atmospheric warming. Statistically, over 99% of the summer snowfall decline is linked to Arctic warming over the past two decades. Based on the reanalysis snowfall data over the ice-covered Arctic Ocean, we derive an estimate for the amount of snow-covered ice. It is estimated that the area of snow-covered ice, and the proportion of sea ice covered by snow, have decreased significantly. We perform a series of sensitivity experiments in which inter-annual changes in snow-covered ice are either unaccounted for, or are parameterized. In the parameterized case, the loss of snow-on-ice results in a substantial decrease in the surface albedo over the Arctic Ocean, that is of comparable magnitude to the decrease in albedo due to the decline in sea ice cover. Accordingly, the solar input to the Arctic Ocean is increased, causing additional surface ice melt. We conclude that the decline in summer snowfall has likely contributed to the thinning of sea ice over recent decades. The results presented provide support for the existence of a positive feedback in association with warming-induced reductions in summer snowfall.” James A. Screen and Ian Simmonds, Climate Dynamics, DOI: 10.1007/s00382-011-1105-2.

Review on biodiversity refugia

Refugia: identifying and understanding safe havens for biodiversity under climate change – Keppel et al. (2011) “Aim  Identifying and protecting refugia is a priority for conservation under projected anthropogenic climate change, because of their demonstrated ability to facilitate the survival of biota under adverse conditions. Refugia are habitats that components of biodiversity retreat to, persist in and can potentially expand from under changing environmental conditions. However, the study and discussion of refugia has often been ad hoc and descriptive in nature. We therefore: (1) provide a habitat-based concept of refugia, and (2) evaluate methods for the identification of refugia.
Location  Global.
Methods  We present a simple conceptual framework for refugia and examine the factors that describe them. We then demonstrate how different disciplines are contributing to our understanding of refugia, and the tools that they provide for identifying and quantifying refugia.
Results  Current understanding of refugia is largely based on Quaternary phylogeographic studies on organisms in North America and Europe during significant temperature fluctuations. This has resulted in gaps in our understanding of refugia, particularly when attempting to apply current theory to forecast anthropogenic climate change. Refugia are environmental habitats with space and time dimensions that operate on evolutionary time-scales and have facilitated the survival of biota under changing environmental conditions for millennia. Therefore, they offer the best chances for survival under climate change for many taxa, making their identification important for conservation under anthropogenic climate change. Several methods from various disciplines provide viable options for achieving this goal.
Main conclusions  The framework developed for refugia allows the identification and description of refugia in any environment. Various methods provide important contributions but each is limited in scope; urging a more integrated approach to identify, define and conserve refugia. Such an approach will facilitate better understanding of refugia and their capacity to act as safe havens under projected anthropogenic climate change.” Gunnar Keppel, Kimberly P. Van Niel, Grant W. Wardell-Johnson, Colin J. Yates, Margaret Byrne, Ladislav Mucina, Antonius G. T. Schut, Stephen D. Hopper, Steven E. Franklin, Global Ecology and Biogeography, DOI: 10.1111/j.1466-8238.2011.00686.x.

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