AGW Observer

Observations of anthropogenic global warming

New research from last week 22/2011

Posted by Ari Jokimäki on June 6, 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:

CO2 doubling at Triassic/Jurassic boundary

Extremely elevated CO2 concentrations at the Triassic/Jurassic boundary – Steinthorsdottir et al. (2011) “Although progress has been made in recent years in reconstructing the environmental conditions at the Triassic/Jurassic Boundary (TJB), published records of atmospheric CO2 concentrations have been of low resolution and/or based on multi-taxon estimates. This is addressed here by reconstructing CO2 concentrations across the TJB using stomatal frequencies of four phylogenetically and ecologically distinct plant groups from two depositionally, geographically and taphonomically seperate boundary sections in East Greenland and Northern Ireland, with stomatal proxy methods and regression analysis. The resulting CO2 records then are compared with an additional existing TJB record from a geological section in Sweden. The final results indicate that pre-TJB (Rhaetian), the CO2 concentration was appoximately 1000 ppm, that it started to rise steeply pre-boundary and had doubled to around 2000–2500 ppm at the TJB. The CO2 concentration then remained evelvated for some time post-boundary, before returning to pre-TJB levels in the Hettangian. These results are in very good accordance with published C-isotope, fire and leaf dissection records, and clearly indicate steeply rising and lingering CO2 concentration at the TJB.” Margret Steinthorsdottir, Andrew J. Jeram and Jennifer C. McElwain, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2011.05.050.

Spain is warming up

Spatial analysis of mean temperature trends in spain over the period 1961–2006 – del Rio et al. (2011) “The spatial distribution of recent mean temperature trends over Spain during the period 1961–2006 at monthly, seasonal and annual time scale is carry out in this study by applying various statistical tools to data from 473 weather stations. The magnitude of trends was derived from the slopes of the linear trends using ordinary least-square fitting. The non parametric Mann-Kendall test was used to determine the statistical significance of trends. Maps of surface temperature trends were generated by applying a geostatistical interpolation technique to visualize the detected tendencies. This study reveals that temperature has generally increased during all months and seasons of the year over the last four decades. More than 60% of whole Spain has evidenced significant positive trends in March, June, August, spring and summer. This percentage diminishes around 40% in April, May and December. Annual temperature has significantly risen in 100% of Spain of around 0.1-0.2 °C/decade according to the Fourth Assessment Report of the IPCC.” S. del Río, L. Herrero, C. Pinto-Gomes and A. Penas, Global and Planetary Change, doi:10.1016/j.gloplacha.2011.05.012.

Pliocene – similar CO2 but warmer than today

Climate and environment of a Pliocene warm world – Salzmann et al. (2011) “The Pliocene Epoch, 5.33 – 2.58 million years ago (Ma), was a generally warmer and wetter interval with atmospheric CO2-concentrations at or slightly above modern levels. This paper provides an overview of Pliocene vegetation, sea surface temperatures and climate modelling outcomes. Most prominent changes in Pliocene biome distribution compared to today include a northwards shift of temperate and boreal vegetation zones in response to a warmer and wetter climate as well as an expansion of tropical savannas and forests at the expense of deserts. Faunal analysis techniques and modelling experiments using the Hadley Centre climate model identified significantly higher Pliocene sea surface temperatures at mid and high latitudes of the northern hemisphere with cooling or unchanged sea surface temperatures at low latitudes. Global mean annual surface temperatures (MAT) are estimated to have been 2 to 3 °C higher during the Piacenzian (3.6-2.58 Ma) than today with a reduced equator to pole gradient. The marine realm during the Pliocene was characterised by a reconfiguration of ocean gateways, particularly the narrowing of the Indonesian Seaway and closure of the Central American Isthmus, which produced essentially a modern pattern of ocean circulation. In the Southern Ocean a warm early Pliocene gave way to late Piacenzian cooling. Proxy data indicate a reduced east to west sea surface temperature gradient in the tropical Pacific during the Pliocene warmth. The Pliocene is one of the most intensively studied geological intervals of the pre-Quaternary. No other warm period in the geological past yields such a unique combination of near modern atmospheric CO2-concentrations, palaeogeography and palaeobiology. However, this paper also identifies data gaps and shortcomings in the reconstruction of Pliocene environments using proxy data and climate models on which future research should focus.” Ulrich Salzmann, Mark Williams, Alan M. Haywood, Andrew L.A. Johnson, Sev Kender and Jan Zalasiewicz, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2011.05.044.

Global warming might show in North Atlantic tides

Rapid change in semi-diurnal tides in the North Atlantic since 1980 – Müller (2011) “An anomalously large trend of M2 and S2 amplitudes and phases, beginning in the early 1980s, is observed in the North Atlantic. Harmonic analysis of long-term sea-level records from tide-gauge stations along the North American Atlantic coast and European Atlantic coast shows a large decrease in M2 and S2 amplitudes and an increase in phase lag. The characteristics of the evolution of M2 and S2 tides are similar, but not fully conclusive, which may suggesting different causes. In general, the trends may be due to global warming, which significantly increased in the early 1980s in the North Atlantic region. Several climate-related driving mechanisms for the observed changes in tides are discussed.” Müller, M. (2011), Geophys. Res. Lett., 38, L11602, doi:10.1029/2011GL047312.

Annually resolved temperature reconstruction from 5Ma

Climate variability in the Early Pliocene Arctic: Annually resolved evidence from stable isotope values of sub-fossil wood, Ellesmere Island, Canada – Csank et al. (2011) “Tree-ring analyses have contributed significantly to investigations of past climate. Stable isotope climate proxies (δ18O, δD and δ13C values) enhance traditional ring-width data, although poor preservation of ancient wood has tended to limit development of stable isotope proxy records to the Holocene and the Late Pleistocene. Here we apply stable isotope techniques to wood that represent the remains of Mixed-Coniferous Boreal Vegetation preserved in Early Pliocene (4–5 Ma) deposits at Strathcona Fiord, Ellesmere Island, Canada (ca. 78°N). Four well-preserved tree trunks, identified through wood anatomical characteristics as Larix (larch), from this high Arctic site provide annually resolved sequences of up to 250 years from which we developed a high-resolution record of Pliocene climate. Stable oxygen isotope values, in conjunction with ring-width measurements were used to derive annually resolved temperature records for this site. Our ring-width and isotope-based reconstructions provide an annually resolved record, up to 250 years, of temperature and indicate growing season (JJ) temperatures (15.8 ± 5.0 °C) 11.8 ± 5.1 °C, and mean annual temperatures (MAT) (− 1.4 ± 4.0 °C) 18.3 ± 4.1 °C warmer than present. Estimated isotope values of precipitation of − 16.3 ± 2 ‰ (δ18O) and − 150.1 ± 8.9 ‰ (δD) were calculated from the isotopic values of wood cellulose. Relative humidity estimated from both δ13C and δD records ranged from 60-80%. Paleotemperature, source water and humidity estimates are comparable to those of a modern Boreal Forest growing ca. 15-20° south of modern Ellesmere Island.” A.Z. Csank, W.P. Patterson, B.M. Eglington, N. Rybczynski and J.F. Basinger, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2011.05.038.


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