Central Pacific El Niño, the “subtropical bridge,” and Eurasian climate - Graf & Zanchettin (2012)Welcome to the inaugural edition of the “New research from last week” in Skeptical Science. This new weekly feature provides a selection of peer-reviewed papers relating to climate science published (or in some cases accepted to be published) in scientific journals during the previous week.
?This is a cross-post from AGW Observer, where this weekly feature has been active since week 40 of 2010. When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. At least some of these are also retweeted in Skeptical Science Twitter page.
In this week's papers El Niño does some moonlighting in Europe. In New Zealand they found some unused sea level measurement stations while in Netherlands they apparently run out of official weather stations and started using weather amateur stations. The pines from Spain are showing the decline, but are doing so selectively. In Australia, they apparently didn't notice YD event at all. There's yet another effort with cosmic ray and climate connection. We also learn how to tell apart climate signal and noise. But did you know that female corals don't like climate change? Or that some Malaria species do seem to like it at least in Thar Desert? This is not all, we have studies also on Paris-London westerly index, dark aerosols, inland waters, and carbon in Siberia. However, this is just a scratch of the surface as there are hundreds of papers published every week relating to climate.
Central Pacific El Niño, the “subtropical bridge,” and Eurasian climate - Graf & Zanchettin (2012)
Abstract: "This study contributes to the discussion on possible effects of El Niño on North Atlantic/European regional climates. We use NCEP/NCAR reanalysis data to show how the two different types of El Niños (the central Pacific, or CP, and the east Pacific, or EP) result in remarkably different European winter temperature anomalies, specifically weak warming during EP and significant cooling during CP El Niños, the latter being associated with a negative phase of the winter North Atlantic Oscillation (NAO). Our results diverge from former suggestions addressing the weakened stratospheric polar vortex as the dominant factor contributing to the El Niño/NAO teleconnection. We propose a tropospheric bridge as the mechanism primarily responsible for the establishment of a negative NAO phase and of associated cold European winters. This mechanism includes the subtropical jet (STJ) waveguide being activated only during CP El Niños, when anomalous convective heating occurs near the edge of the Pacific warm pool. Under these conditions the STJ is enhanced by planetary wave flux divergence in the subtropical upper troposphere, providing favorable conditions for the propagation of a wave number 5 disturbance around the subtropical Northern Hemisphere. This wave contributes to weakening of the Azores High and, hence, to the negative NAO phase. As global warming scenarios project an increase in the frequency of CP El Niño events, the distinctive nature of this mechanism implies that the probability of cold European winters may increase as well in future decades."
Citation: Graf, H.-F., and D. Zanchettin (2012), J. Geophys. Res., 117, D01102, doi:10.1029/2011JD016493.
Regional sea level trends in New Zealand - Hannah & Bell (2012)
Abstract: "In terms of sea level data sets able to be used for long-term sea level trend analysis, the Southern Hemisphere is a data sparse region of the world. New Zealand lies in this region, presently having four (major port) data sets used for such trend analysis. This paper describes the process followed to compute new sea level trends at another six ports, each with very discontinuous tide gauge records. In each case the tide gauge has previously only been used for precisely defining an historical local Mean Sea Level (MSL) datum. The process used involved a comparison of the old MSL datum with a newly defined datum obtained from sea level data covering the last decade. A simple linear trend was fitted between the two data points. Efforts were then made to assess possible bias in the results due to oceanographic factors such as the El Niño–Southern Oscillation (ENSO) cycle, and the Interdecadal Pacific Oscillation (IPO). This was done by taking the longer time series from the four major ports and assessing the spatially coherent variability in annual sea level using the dominant principal component from an empirical orthogonal function (EOF) analysis. The average relative sea level rise calculated from these six newly derived trends was 1.7 ± 0.1 mm yr−1, a result that is completely consistent with the analysis of the long-term gauge records. Most importantly, it offers a relatively simple method of improving our knowledge of relative sea level trends in data sparse regions of the world."
Citation: Hannah, J., and R. G. Bell (2012), J. Geophys. Res., 117, C01004, doi:10.1029/2011JC007591.
Abstract: "A better quantification of the urban heat islands in the Netherlands is urgent, due to heat stress related problems in the recent past combined with the expected temperature rise for the coming decades. However, professional temperature observations in Dutch urban areas are scarce. Therefore, in this research we have explored the use of observations from weather stations installed and maintained by weather amateurs. From a set of over 200 stations, suitable and representative data have been selected from 20 stations, using a set of objective selection criteria based on metadata. One year of data (Jan-Dec 2010) was considered. From these data we have obtained estimates of the magnitude of the UHI in Dutch low-rise residential areas. A positive relation (linear model r-squared ≈ 0.7) was derived between the summer-averaged UHI and the (neighborhood-scale) population density around the observational sites. It was found that the UHI in summer is strongest in nighttime conditions, and increases with decreasing wind speed and decreasing cloud cover, and with increasing sea level air pressure. The summer-averaged UHI was around 0.9°C. During nighttime in a relatively warm one-month subperiod of the summer the average UHI was around 1.4°C. During spring and autumn the UHI was lower than in summer, during winter no significant UHI was observed. The agreement in results between the different stations, and the accordance of the magnitude and variation of the observed UHI to literature, show that automatic observations from weather amateurs can be sufficient quality for atmospheric research, provided that detailed metadata are available."
Citation: Dirk Wolters and Theo Brandsma, Journal of Applied Meteorology and Climatology 2012, doi: http://dx.doi.org/10.1175/JAMC-D-11-0135.1.
Abstract: "The negative impacts of severe drought on the growth and vigor of tree species and their relationship with forest decline have not been properly evaluated taking into account the differential responses to such stress of trees, sites and species. We evaluated these responses by quantifying the changes in radial growth of plantations of four pine species (Pinus sylvestris, Pinus nigra, Pinus pinaster, Pinus halepensis) which showed distinct decline and defoliation levels in southeastern Spain. We used dendrochronological methods, defoliation records, linear mixed models of basal area increment and dynamic factor analysis to quantify the responses of trees at the species and individual scales to site conditions and drought stress. In the region a temperature rise and a decrease in spring precipitation have led to drier conditions during the late twentieth century characterized by severe droughts in the 1990s and 2000s. As expected, the defoliation levels and the reductions in basal area increment were higher in those species more vulnerable to drought-induced xylem embolism (P. sylvestris) than in those more resistant (P. halepensis). Species adapted to xeric conditions but with high growth rates, such as P. pinaster, were also vulnerable to drought-induced decline. The reduction in basal area increment and the defoliation events occurred after consecutive severe droughts. A decrease in spring precipitation, which is the main driver of radial growth, is the most plausible cause of recent forest decline. The sharp growth reduction and widespread defoliation of the most affected pine plantations of Scots pine make their future persistence in drought-prone sites unlikely under the forecasted warmer and drier conditions."
Citation: Raúl Sánchez-Salguero, Rafael M. Navarro-Cerrillo, J. Julio Camarero and Ángel Fernández-Cancio, Climatic Change, DOI: 10.1007/s10584-011-0372-6.
Two other studies were published last week on pine tree rings:
The Younger Dryas: relevant in the Australian region? - Tibby (2012)
Abstract: "An assessment of Australian climate during the Younger Dryas Chronozone (YDC) is presented. This review focuses on securely dated records from sites of continuous deposition, placing greatest emphasis on temperature reconstructions, with records of effective precipitation (i.e. the combined effect of precipitation minus evapotranspiration) also considered. While there is a paucity of Australian records covering the last glacial interglacial transition, particularly those which directly infer temperature, sufficient data exist to examine YDC climate from southern and eastern Australia. Temperature reconstructions from Tasmania, based on both chironomid and pollen data, show no evidence for Younger Dryas cooling. By contrast, there is evidence for cooling associated with the Antarctic Cold Reversal, from Tullabardine Dam pollen data and the sediment organic content from Eagle and Platypus Tarns in Tasmania. Records from a number of eastern Australian mainland sites provide no evidence of effective precipitation shifts concurrent with the Younger Dryas Chronozone. Similarly, reconstructions of discharge from the Murray-Darling Basin, which covers a large proportion (14%) of the Australian continent, and dust transport from a larger portion of the continent also show no evidence of climate shifts concomitant with the Younger Dryas. Of research published in the past decade, only one study, located in the Great Australian Bight, claims evidence of a YDC cooling (Andres et al., 2003). By contrast, this review suggests that there is no conclusive evidence for cooling, or indeed any distinctive climate patterning, during the Younger Dryas Chronozone in Australia."
Citation: John Tibby, Quaternary International, doi:10.1016/j.quaint.2012.01.003.
Time of emergence of climate signals - Hawkins & Sutton (2012) [FULL TEXT]
Abstract: "The time at which the signal of climate change emerges from the noise of natural climate variability (Time of Emergence, ToE) is a key variable for climate predictions and risk assessments. Here we present a methodology for estimating ToE for individual climate models, and use it to make maps of ToE for surface air temperature (SAT) based on the CMIP3 global climate models. Consistent with previous studies we show that the median ToE occurs several decades sooner in low latitudes, particularly in boreal summer, than in mid-latitudes. We also show that the median ToE in the Arctic occurs sooner in boreal winter than in boreal summer. A key new aspect of our study is that we quantify the uncertainty in ToE that arises not only from inter-model differences in the magnitude of the climate change signal, but also from large differences in the simulation of natural climate variability. The uncertainty in ToE is at least 30 years in the regions examined, and as much as 60 years in some regions. Alternative emissions scenarios lead to changes in both the median ToE (by a decade or more) and its uncertainty. The SRES B1 scenario is associated with a very large uncertainty in ToE in some regions. Our findings have important implications for climate modelling and climate policy which we discuss."
Citation: Hawkins, E. and R. Sutton (2012), Geophys. Res. Lett., 39, L01702, doi:10.1029/2011GL050087.
Abstract: "A westerly index for Europe is developed back to 1692 using newly recovered and corrected Mean Sea-level Pressure (MSLP) data from London and Paris. The index is compared against various instrumental and proxy indices of the North Atlantic Oscillation (NAO). In the winter, the Paris-London index depicts a spatial pattern of atmospheric circulation that is bi-modal, with centres of action that are shifted eastwards compared to the NAO. Owing to asymmetry in the NAO the Paris-London index provides a good depiction of positive NAO conditions as well as extreme negative phases of the NAO that arise from reversals of the pressure centres, but less extreme negative NAO conditions are associated with westerly index values approaching zero. The merit in using the Paris-London index lies with its consistency over time as a measure of westerly wind flow, which may not be the case with other proxy-based indices. In the summer, the Paris-London index bears a close relationship to the reconstructed high-summer NAO series of Folland et al. (2009) as well as the summer Luterbacher et al. (1999) NAO reconstruction. An important finding is that the summer NAO was highly variable during the early nineteenth century but was predominately positive on the decadal time scale during that period. Since circa 1970 the summer index has mostly been negative, indicating reduced westerlies and increased blocking conditions that are exceptional in the context of the last 250 years."
Citation: Richard C. Cornes, Philip D. Jones, Keith R. Briffa, Timothy J. Osborn, International Journal of Climatology, DOI: 10.1002/joc.3416.
Cosmic rays and space weather: effects on global climate change - Dorman (2012) [FULL TEXT]
Comments: This paper makes a case for strong effect of cosmic rays on climate. However, the paper seems to ignore most of the papers showing evidence against the cosmic ray hypothesis. There are plenty of such papers. Discussion section mentions couple of them in passing but otherwise they are ignored. Paper also seems to use very old data, as is evident for example in Figures 2, 3, and 4, but newer data is not touched.
Abstract: "We consider possible effects of cosmic rays and some other space factors on the Earth's climate change. It is well known that the system of internal and external factors formatting the climate is very unstable; decreasing planetary temperature leads to an increase of snow surface, and decrease of the total solar energy input into the system decreases the planetary temperature even more, etc. From this it follows that even energetically small factors may have a big influence on climate change. In our opinion, the most important of these factors are cosmic rays and cosmic dust through their influence on clouds, and thus, on climate."
Citation: Dorman, L. I., Ann. Geophys., 30, 9-19, doi:10.5194/angeo-30-9-2012, 2012.
Abstract: "Climatic variability and rise in temperature are considered as the key determinants to the transmission of malaria. In the present study, the trends in the cases of malaria caused by Plasmodium falciparum and Plasmodium vivax were investigated by using the nonparametric Mann-Kendall test after removing the effect of significant lag-1 serial correlation from the time series of cases of malaria incidence by pre-whitening in annual, seasonal, and monthly time scales at Bikaner, located in the Thar Desert of Rajasthan, in northwest India. Multi-collinearity within the datasets under consideration was investigated by means of correlation matrix, the Bartlett sphericity test, and the Kaiser-Meyer-Olkin measure of sampling adequacy, subsequent to which it was removed by using principal component analysis. Finally, artificial neural network models were employed to predict cases of malaria incidence caused by P. falciparum and P. vivax at various scales. During the last 34 years from 1975 to 2008, P. falciparum malaria incidence cases have been found to increase significantly corresponding to monthly (April and September) and seasonal (monsoon) time scales over Bikaner. On the other hand, no significant trends were observed in P. vivax malaria cases at Bikaner. Concomitant increases in P. falciparum cases of malaria incidence and observed temperature increases at Bikaner hint that P. falciparum malaria may have grown significantly under the warming climate of the Thar Desert."
Citation: Deepak Jhajharia, Surajit Chattopadhyay, Rahul R. Choudhary, Vas Dev, Vijay P. Singh, Shankar Lal, International Journal of Climatology, DOI: 10.1002/joc.3424.
On carbon transport and fate in the East Siberian Arctic land–shelf–atmosphere system - Semiletov et al. (2012) [FULL TEXT]
Abstract: "This review paper summarizes current understanding of the transport of organic carbon to, and the fate of organic carbon within, the East Siberian Arctic Shelf (ESAS), and of processes determining carbon dioxide (CO2) and methane (CH4) fluxes from the ESAS to the atmosphere achieved from analyzing the data sets obtained on 20 expeditions performed from 1999 to 2011. This study of the ESAS was aimed at investigating how redistribution of old carbon from degrading terrestrial and sub-sea permafrost and from coastal erosion contributes to the carbon pool of the ESAS, how changes in the hydrological cycle of the surrounding land and alteration of terrestrial carbon cycles affect the hydrological and biogeochemical parameters of shelf water masses, and which factors control CH4 and CO2 emissions from the ESAS. This report describes selected results achieved by a developing international scientific partnership that has been crucial at every stage of the study and will be even more important in the future."
Citation: Igor P Semiletov et al 2012 Environ. Res. Lett. 7 015201 doi:10.1088/1748-9326/7/1/015201. [Full text]
An investigation of the calcification response of the scleractinian coral Astrangia poculata to elevated pCO2 and the effects of nutrients, zooxanthellae and gender - Holcomb et al. (2012) [FULL TEXT]
Abstract: "The effects of nutrients and pCO2 on zooxanthellate and azooxanthellate colonies of the temperate scleractinian coral Astrangia poculata (Ellis and Solander, 1786) were investigated at two different temperatures (16 °C and 24 °C). Corals exposed to elevated pCO2 tended to have lower relative calcification rates, as estimated from changes in buoyant weights. Experimental nutrient enrichments had no significant effect nor did there appear to be any interaction between pCO2 and nutrients. Elevated pCO2 appeared to have a similar effect on coral calcification whether zooxanthellae were present or absent at 16 °C. However, at 24 °C, the interpretation of the results is complicated by a significant interaction between gender and pCO2 for spawning corals. At 16 °C, gamete release was not observed, and no gender differences in calcification rates were observed – female and male corals showed similar reductions in calcification rates in response to elevated CO2 (15% and 19% respectively). Corals grown at 24 °C spawned repeatedly and male and female corals exhibited two different growth rate patterns – female corals grown at 24 °C and exposed to CO2 had calcification rates 39% lower than females grown at ambient CO2, while males showed a non-significant decline of 5% under elevated CO2. The increased sensitivity of females to elevated pCO2 may reflect a greater investment of energy in reproduction (egg production) relative to males (sperm production). These results suggest that both gender and spawning are important factors in determining the sensitivity of corals to ocean acidification, and considering these factors in future research may be critical to predicting how the population structures of marine calcifiers will change in response to ocean acidification."
Citation: Holcomb, M., Cohen, A. L., and McCorkle, D. C., Biogeosciences, 9, 29-39, doi:10.5194/bg-9-29-2012, 2012.
Abstract: "Organic carbon (OC) burial and greenhouse gas emission of inland waters plays an increasingly evident role in the carbon balance of the continents, and particularly young reservoirs in the tropics emit methane (CH4) at high rates. Here we show that an old, temperate reservoir acts simultaneously as a strong OC sink and CH4 source, because the high sedimentation rate supplies reactive organic matter to deep, anoxic sediment strata, fuelling methanogenesis and gas bubble emission (ebullition) of CH4 from the sediment. Damming of the river has resulted in the build-up of highly methanogenic sediments under a shallow water column, facilitating the transformation of fixed CO2 to atmospheric CH4. Similar high OC burial and CH4 ebullition is expected in other reservoirs and natural river deltas."
Citation: Sobek, S., T. DelSontro, N. Wongfun, and B. Wehrli (2012), Geophys. Res. Lett., 39, L01401, doi:10.1029/2011GL050144.
Direct and semi-direct radiative forcing of smoke aerosols over clouds - Wilcox (2012) [FULL TEXT]
Abstract: "Observations from Earth observing satellites indicate that dark carbonaceous aerosols that absorb solar radiation are widespread in the tropics and subtropics. When these aerosols mix with clouds, there is generally a reduction of cloudiness owing to absorption of solar energy in the aerosol layer. Over the subtropical South Atlantic Ocean, where smoke from savannah burning in southern Africa resides above a persistent deck of marine stratocumulus clouds, radiative heating of the smoke layer leads to a thickening of the cloud layer. Here, satellite observations of the albedo of overcast scenes of 25 km2 size or larger are combined with additional satellite observations of clouds and aerosols to estimate the top-of-atmosphere direct radiative forcing attributable to presence of dark aerosol above bright cloud, and the negative semi-direct forcing attributable to the thickening of the cloud layer. The average positive direct radiative forcing by smoke over an overcast scene is 9.2±6.6 W m−2 for cases with an unambiguous signal of absorbing aerosol over cloud in passive ultraviolet remote sensing observations. However, cloud liquid water path is enhanced by 16.3±7.7 g m−2 across the range of values for sea surface temperature for cases of smoke over cloud. The negative radiative forcing associated with this semi-direct effect of smoke over clouds is estimated to be −5.9±3.5 W m−2. Therefore, the cooling associated with the semi-direct cloud thickening effect compensates for greater than 60 % of the direct radiative effect. Accounting for the frequency of occurrence of significant absorbing aerosol above overcast scenes leads to an estimate of the average direct forcing of 1.0±0.7 W m−2 contributed by these scenes averaged over the subtropical southeast Atlantic Ocean during austral winter. The regional average of the negative semi-direct forcing is −0.7±0.4 W m−2. Therefore, smoke aerosols overlaying the decks of overcast marine stratocumulus clouds considered here yield a small net positive radiative forcing, which results from the difference of two larger effects."
Citation: Wilcox, E. M., Atmos. Chem. Phys., 12, 139-149, doi:10.5194/acp-12-139-2012, 2012.
Cloudiness as a Global Climatic Feedback Mechanism: The Effects on the Radiation Balance and Surface Temperature of Variations in Cloudiness - Schneider (1972) [FULL TEXT]
Abstract: "The effect of variation in cloudiness on the climate is considered in terms of 1) a relation between the radiation balance of the earth-atmosphere system and variations in the amount of cloud cover or effective cloud top height, 2) the effect on the surface temperature of variations in cloudiness, and 3) the dynamic coupling or “feedback” effects relating changes in surface temperature to the formation of clouds. The first two points are studied by numerical integration of a simple radiation flux model, and the third point is discussed qualitatively. Global-average radiation balance calculations show that an increase in the amount of low and middle level cloud cover (with cloud top height and cloud albedo fixed) decreases the surface temperature. But, this result for the global-average case does not hold near polar regions, where the albedo of the cloudy areas can he comparable to (or even smaller than) the albedo of the snow-covered cloudless areas, and where, especially in the winter season, the amount of incoming solar radiation at high latitudes is much less than the global-average value of insolation. The exact latitude at which surface cooling changes to surface warming from a given increase in cloud cover amount depends critically upon the local values of the cloud albedo and the albedo of the cloudless areas that are used in the calculation. However, an increase in effective cloud top height (with cloud cover and cloud albedo fixed) increases the surface temperature at all latitudes."
Citation: Schneider, Stephen H., 1972, J. Atmos. Sci., 29, 1413–1422, doi: http://dx.doi.org/10.1175/1520-0469(1972)029<1413:CAAGCF>2.0.CO;2.
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.
Posted by Ari Jokimäki on Tuesday, 10 January, 2012
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