AGW Observer

Observations of anthropogenic global warming

New research from last week 13/2011

Posted by Ari Jokimäki on April 4, 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:

Planetary albedo decreases when planet warms

Atmospheric and surface contributions to planetary albedo – Donohoe & Battisti (2011) “The planetary albedo is partitioned into a component due to atmospheric reflection and a component due to surface reflection by using shortwave fluxes at the surface and top of the atmosphere in conjunction with a simple radiation model. The vast majority of the observed global average planetary albedo (88%) is due to atmospheric reflection. Surface reflection makes a relatively small contribution to planetary albedo because the atmosphere attenuates the surface contribution to planetary albedo by a factor of approximately three. The global average planetary albedo in the ensemble average of the CMIP3 pre-industrial simulations is also primarily (87%) due to atmospheric albedo. The inter-model spread in planetary albedo is relatively large and is found to be predominantly a consequence of inter-model differences in atmospheric albedo, with surface processes playing a much smaller role despite significant inter-model differences in surface albedo. The CMIP3 models show a decrease in planetary albedo under a doubling of carbon dioxide – also primarily due to changes in atmospheric reflection (which explains more than 90% of the inter-model spread). All models show a decrease in planetary albedo due to the lowered surface albedo associated with a contraction of the cryosphere in a warmer world, but this effect is small compared to the spread in planetary albedo due to model differences in the change in clouds.” Aaron Donohoe and David S. Battisti, Journal of Climate 2011, doi: 10.1175/2011JCLI3946.1. [Full text]

Antarctic thermostat for global deepwater

On the linkage between Antarctic surface-water stratification and global deepwater temperature – Keeling & Visbeck (2011) “The suggestion is advanced that the remarkably low static stability of Antarctic surface waters may arise from a feedback loop involving global deepwater temperatures. If deepwater temperatures are too warm, this promotes Antarctic convection, thereby strengthening the inflow of Antarctic Bottom Water into the ocean interior and cooling the deep ocean. If deepwaters are too cold, this promotes Antarctic stratification allowing the deep ocean to warm because of the input of North Atlantic Deep Water. A steady-state deepwater temperature is achieved such that the Antarctic surface can barely undergo convection. A two-box model is used to illustrate this feedback loop in its simplest expression and to develop basic concepts, such as the bounds on the operation of this loop. The model illustrates the possible dominating influence of Antarctic upwelling rate and Antarctic freshwater balance on global deepwater temperatures.” Ralph F. Keeling, Martin Visbeck, Journal of Climate 2011, doi: 10.1175/2011JCLI3642.1. [Full text]

Environmental reconstruction from intestinal contents of baby mammoth

Environmental Reconstruction Inferred From The Intestinal Contents Of The Yamal Baby Mammoth Lyuba (Mammuthus Primigenius Blumenbach, 1799) – Kosintsev et al. (2011) “The article presents the results of a complex investigation of the intestinal content of the frozen mummy of a baby woolly mammoth (Mammuthus primigenius Blumenbach, 1799) found in 2007 in the Yamal Peninsula (Western Siberia). The mummy belongs to a female mammoth calf approximately 1–1.5 months of age, and it has been named “Lyuba”. Analysis of bone tissue yielded a 14C date of 41910 (+550/-450) years ago. Analysis of detritus material from the large intestine yielded a 14C date of 41700 (+700/-550) years ago. These dates practically coincide, thus denoting synchronism of the time of the baby mammoth’s death and the formation of its intestinal contents. This time correspond to the middle part of MIS-3, or the Middle Weichselian Pleniglacial. Pollen, phytolith, plant macrofossil and mineral analyses of the intestinal content were carried out. Reconstruction of the environment where the baby mammoth lived is given based on the intestinal content analyses. The data suggest that the baby mammoth lived in tundra-like landscapes dominated by grass-sedge communities with forbs and Betula nana.” Pavel A. Kosintsev, Elena G. Lapteva, Svetlana S. Trofimova, Oksana G. Zanina, Aleksey N. Tikhonov and Johannes Van der Plicht, Quaternary International, doi:10.1016/j.quaint.2011.03.027.

Proglacial lake discharges near the beginning of YD event

Timing and duration of North American glacial lake discharges and the Younger Dryas climate reversal – Rayburn et al. (2011) “Radiocarbon-dated sediment cores from the Champlain Valley (northeastern USA) contain stratigraphic and micropaleontologic evidence for multiple, high-magnitude, freshwater discharges from North American proglacial lakes to the North Atlantic. Of particular interest are two large, closely spaced outflows that entered the North Atlantic Ocean via the St. Lawrence estuary about 13,200–12,900 cal yr BP, near the beginning of the Younger Dryas cold event. We estimate from varve chronology, sedimentation rates and proglacial lake volumes that the duration of the first outflow was less than 1 yr and its discharge was approximately 0.1 Sv (1 Sverdrup = 106 m3 s−1). The second outflow lasted about a century with a sustained discharge sufficient to keep the Champlain Sea relatively fresh for its duration. According to climate models, both outflows may have had sufficient discharge, duration and timing to affect meridional ocean circulation and climate. In this report we compare the proglacial lake discharge record in the Champlain and St. Lawrence valleys to paleoclimate records from Greenland Ice cores and Cariaco Basin and discuss the two-step nature of the inception of the Younger Dryas.” John A. Rayburn, Thomas M. Cronin, David A. Franzi, Peter L.K. Knuepfer and Debra A. Willard, Quaternary Research, doi:10.1016/j.yqres.2011.02.004.

Climate change and forest shifts in Siberia

Climate change and climate-induced hot spots in forest shifts in central Siberia from observed data – Tchebakova et al. (2011) “Regional Siberian studies have already registered climate warming over the last several decades. We evaluated ongoing climate change in central Siberia between 1991 and 2010 and a baseline period, 1961–1990, and between 1991 and 2010 and Hadley 2020 climate change projections, represented by the moderate B1 and severe A2 scenarios. Our analysis showed that winters are already 2–3°C warmer in the north and 1–2°C warmer in the south by 2010. Summer temperatures increased by 1°C in the north and by 1–2°C in the south. Change in precipitation is more complicated, increasing on average 10% in middle latitudes and decreasing 10–20% in the south, promoting local drying in already dry landscapes. Hot spots of possible forest shifts are modeled using our Siberian bioclimatic vegetation model and mountain vegetation model with respect to climate anomalies observed pre-2010 and predicted 2020 Hadley scenarios. Forests are predicted to shift northwards along the central Siberian Plateau and upslope in both the northern and southern mountains. South of the central Siberian Plateau, steppe advancement is predicted that was previously non-existent north of 56°N latitude. South of 56°N, steppe expansion is predicted in the dry environments of Khakasiya and Tyva. In the southern mountains, it is predicted that the lower tree line will migrate upslope due to increased dryness in the intermontane Tyvan basins. The hot spots of vegetation change that are predicted by our models are confirmed by regional literature data.” N. M. Tchebakova, E. I. Parfenova and A. J. Soja, Regional Environmental Change, DOI: 10.1007/s10113-011-0210-4.

Below ground ecosystem in high Arctic not yet affected by global warming

A high arctic soil ecosystem resists long-term environmental manipulations – Lamb et al. (2011) “We evaluated above and below ground ecosystem changes in a 16 year, combined fertilization and warming experiment in a High Arctic tundra deciduous shrub heath (Alexandra Fiord, Ellesmere Island, NU, Canada). Soil emissions of the three key greenhouse gases (carbon dioxide, methane, and nitrous oxide) were measured in mid July 2009 using soil respiration chambers attached to a FTIR system. Soil chemical and biochemical properties including Q10 values for CO2, CH4, and N2O, Bacteria and Archaea assemblage composition, and the diversity and prevalence of key nitrogen cycling genes including bacterial amoA, crenarchaeal amoA, and nosZ were measured. Warming and fertilization caused strong increases in plant community cover and height but had limited effects on greenhouse gas fluxes and no substantial effect on soil chemistry or biochemistry. Similarly, there was a surprising lack of directional shifts in the soil microbial community as a whole or any change at all in microbial functional groups associated with CH4 consumption or N2O cycling in any treatment. Thus, it appears that while warming and increased nutrient availability have strongly affected the plant community over the last 16 years, the below ground ecosystem has not yet responded. This resistance of the soil ecosystem has resulted in limited changes in greenhouse gas fluxes in response to the experimental treatments.” Eric G. Lamb, Sukkyun Han, Brian D. Lanoil, Greg H. R. Henry, Martin E. Brummell, Samiran Banerjee, Steven D. Siciliano, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02431.x.

Willow tit and its caterpillar food synchronized better due to climate change

Warming climate advances breeding and improves synchrony of food demand and food availability in a boreal passerine – Vatka et al. (2011) “Global climate change affects ecosystems via several trophic levels. We investigated changes in the timing of breeding in the willow tit (Poecile montanus) and timing of its caterpillar food resource in relation to warming springs in a boreal forest. We used generalized linear mixed effect models to study the importance of synchrony between the timing of breeding in willow tits and the caterpillar food availability on the breeding success, measured as nestling survival rate and mean nestling weight. Both the timing of breeding and the timing of the caterpillar peak advanced during the last decades, and were well explained by spring temperatures. Unlike in most passerine populations studied, synchrony has improved with rising spring temperatures. However, it had only a modest although statistically significant positive influence on breeding success. Spring temperatures do not seem to be used as cues for the timing of caterpillar food availability by willow tits. We conclude that responses to climatic warming seem to be population, species and habitat specific, necessitating research in a wide range of taxa in different climatic zones.” Emma Vatka, Markku Orell, Seppo Rytkönen, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02430.x.

Greenland ice sheet might melt faster than expected

The Greenland Ice Sheet Response to Transient Climate Change – Ren et al. (2011) “This study applies a multi-phase, multiple-rheology, scalable and extensible geofluid model to the Greenland Ice Sheet (GrIS). The model is driven by monthly atmospheric forcing from global climate model simulations. Novel features of the model, referred to as SEGMENT-Ice, include using the full Navier-Stokes equations to account for non-local dynamic balance and its influence on ice flow; and a granular sliding layer between the bottom ice layer and the lithosphere layer to provide a mechanism for possible large scale surges in a warmer future climate (granular basal layer is for certain specific region, though). Monthly climate of SEGMENT-Ice allows an investigation of detailed features such as seasonal melt area extent (SME) over Greenland. The model reproduced reasonably well the annual maximum SME and total ice mass lost rate when compared observations from the Special Sensing Microwave Imager (SSM/I) and Gravity Recovery and Climate Experiment (GRACE) over the past few decades. The SEGMENT-Ice simulations are driven by projections from two relatively high-resolution climate models, the NCAR-CCSM3 and MIROC3.2-hires models, under a realistic 21st century greenhouse gas emission scenario. They suggest that the surface flow would be enhanced over the entire GrIS, due to a reduction of ice viscosity as the temperature increases, despite of small change in the ice surface topography over the interior of Greenland. With increased surface flow speed, strain-heating induces more rapid heating in the ice at levels deeper than due to diffusion alone. Basal sliding, especially for granular sediments, provides an efficient mechanism for fast-glacier acceleration and enhanced mass loss. This mechanism, absent from other models, provides a rapid dynamic response to climate change. Net mass loss estimates from the new model should reach ~220 km3/yr by 2100, significantly higher than estimates by the IPCC AR4 of ~50–100 km3/yr. By 2100, the perennial frozen surface area decreases up to ~60%; to ~7×105 km2, indicating a massive expansion of the ablation zone. Ice mass change patterns, particularly along the periphery, are very similar between the two climate models.” Diandong Ren, Rong Fu, Lance M. Leslie, Jianli Chen, Clark R. Wilson and David J. Karoly, Journal of Climate 2011, doi: 10.1175/2011JCLI3708.1.

Spectral measurements of CO2 and CH4 concentrations

Long-term analysis of carbon dioxide and methane column-averaged mole fractions retrieved from SCIAMACHY – Schneising et al. (2011) “Carbon dioxide (CO2) and methane (CH4) are the two most important anthropogenic greenhouse gases contributing to global climate change. SCIAMACHY onboard ENVISAT (launch 2002) was the first and is now with TANSO onboard GOSAT (launch 2009) one of only two satellite instruments currently in space whose measurements are sensitive to CO2 and CH4 concentration changes in the lowest atmospheric layers where the variability due to sources and sinks is largest. We present long-term SCIAMACHY retrievals (2003–2009) of column-averaged dry air mole fractions of both gases (denoted XCO2 and XCH4) derived from absorption bands in the near-infrared/shortwave-infrared (NIR/SWIR) spectral region focusing on large-scale features. The results are obtained using an upgraded version (v2) of the retrieval algorithm WFM-DOAS including several improvements, while simultaneously maintaining its high processing speed. The retrieved mole fractions are compared to global model simulations (CarbonTracker XCO2 and TM5 XCH4) being optimised by assimilating highly accurate surface measurements from the NOAA/ESRL network and taking the SCIAMACHY averaging kernels into account. The comparisons address seasonal variations and long-term characteristics. The steady increase of atmospheric carbon dioxide primarily caused by the burning of fossil fuels can be clearly observed with SCIAMACHY globally. The retrieved global annual mean XCO2 increase agrees with CarbonTracker within the error bars (1.80±0.13 ppm yr−1 compared to 1.81±0.09 ppm yr−1). The amplitude of the XCO2 seasonal cycle as retrieved by SCIAMACHY, which is 4.3±0.2 ppm for the Northern Hemisphere and 1.4±0.2 ppm for the Southern Hemisphere, is on average about 1 ppm larger than for CarbonTracker. An investigation of the boreal forest carbon uptake during the growing season via the analysis of longitudinal gradients shows good agreement between SCIAMACHY and CarbonTracker concerning the overall magnitude of the gradients and their annual variations. The analysis includes a discussion of the relative uptake strengths of the Russian and North American boreal forest regions. The retrieved XCH4 results show that after years of stability, atmospheric methane has started to rise again in recent years which is consistent with surface measurements. The largest increase is observed for the tropics and northern mid- and high-latitudes amounting to about 7.5±1.5 ppb yr−1 since 2007. Due care has been exercised to minimise the influence of detector degradation on the quantitative estimate of this anomaly.” Schneising, O., Buchwitz, M., Reuter, M., Heymann, J., Bovensmann, H., and Burrows, J. P., Atmos. Chem. Phys., 11, 2863-2880, doi:10.5194/acp-11-2863-2011, 2011. [full text]

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