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New research from last week 39/2012
Posted on 2 October 2012 by Ari Jokimäki
Studies from Africa have so far been rather rare in these weekly batches but this week we have two papers from Nigeria. They are about farmers and forests. We also have studies on Atlantic Warm Pool corals, atmospheric carbon dioxide, coal burning, coastal heat waves, climate effect of cosmic rays, Swiss forests, NAO state, and of course we have our weekly Arctic sea ice paper. Well, ok, in the other paper section we also have couple of Arctic sea ice papers. Permafrost also gets treated with couple of papers there. And... well, for the rest, see them yourself.
Positive and negative climatic effects from afforestation in Nigeria
Abstract: "Afforestation is usually thought as a good approach to mitigate impacts of warming over a region. This study presents an argument that afforestation may have bigger impacts than originally thought by previous studies. The study investigates the impacts of afforestation on future climate and extreme events in Nigeria, using a regional climate model (RegCM3), forced with global climate model simulations. The impacts of seven afforestation options on the near future (2031–2050, under A1B scenario) climate and the extreme events are investigated. RegCM3 replicates essential features in the present-day (1981–2000) climate and the associated extreme events, and adequately simulates the seasonal variations over the ecological zones in the country. However, the model simulates the seasonal climate better over the northern ecological zones than over the southern ecological zones. The simulated spatial distribution of the extreme events agrees well with the observation, though the magnitude of the simulated events is smaller than the observed. The study shows that afforestation in Nigeria could have both positive and negative future impacts on the climate change and extreme events in the country. While afforestation reduces the projected global warming and enhances rainfall over the afforested area (and over coastal zones), it enhances the warming and reduces the rainfall over the north-eastern part of the country. In addition, the afforestation induces more frequent occurrence of extreme rainfall events (flooding) over the coastal region and more frequent occurrence of heat waves and droughts over the semi-arid region. The positive and negative impacts of the afforestation are not limited to Nigeria; they extend to the neighboring countries. While afforestation lowers the warming and enhances rainfall over Benin Republic, it increases the warming and lowers the rainfall over Niger, Chad and Cameroon. The result of the study has important implication for the ongoing climate change mitigation and adaptation efforts in Nigeria."
Citation: Babatunde J. Abiodun, Ayobami T. Salami, Olaniran J. Matthew and Sola Odedokun, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1523-9.
Atlantic Warm Pool corals as recorders of sea surface temperature
Abstract: "Accurate low-latitude sea surface temperature (SST) records that predate the instrumental era are needed to put recent warming in the context of natural climate variability, and to evaluate the persistence of lower frequency climate variability prior to the instrumental era and the possible influence of anthropogenic climate change on this variability. Here we present a 235-year long SST reconstruction based on annual growth rates (linear extension) of three colonies of the Atlantic coral Siderastrea siderea sampled at two sites on the northeastern Yucatan Peninsula, Mexico, located within the Atlantic Warm Pool (AWP). AWP SSTs vary in concert the Atlantic Multidecadal Oscillation (AMO), a basin-wide, quasi-periodic (~60-80 years) oscillation of North Atlantic SSTs. We demonstrate that the annual linear growth rates of all three coral colonies are significantly inversely correlated with SST. We calibrate annual linear growth rates to SST between 1900 and 1960 AD. The linear correlation coefficient over the calibration period is r = -0.77, and -0.66 over the instrumental record (1860-2008 AD). We apply our calibration to annual linear growth rates to extend the SST record to 1775AD and show that multi-decadal SST variability has been a persistent feature of the AWP, and likely, of the North Atlantic over this time period. Our results imply that tropical Atlantic SSTs remained within 1 {degree sign}C of modern values during the past 225 years, consistent with a previous reconstruction based on coral growth rates and with most estimates based on the Mg/Ca of planktonic foraminifera from marine sediments."
Citation: Vásquez-Bedoya, L. F., A. L. Cohen, D. W. Oppo, and P. Blanchon (2012), Corals record persistent multidecadal SST variability in the Atlantic Warm Pool since 1775AD, Paleoceanography, doi:10.1029/2012PA002313.
Abrupt change in atmospheric carbon dioxide during the last ice age
Abrupt change in atmospheric CO2 during the last ice age - Ahn et al. (2012)
Abstract: "During the last glacial period atmospheric carbon dioxide and temperature in Antarctica varied in a similar fashion on millennial time scales, but previous work indicates that these changes were gradual. In a detailed analysis of one event we now find that approximately half of the CO2 increase that occurred during the 1500-year cold period between Dansgaard-Oeschger (DO) events 8 and 9 happened rapidly, over less than two centuries. This rise in CO2 was synchronous with, or slightly later than, a rapid increase of Antarctic temperature inferred from stable isotopes."
Citation: Ahn, J., E. Brook, A. Schmittner, and K. J. Kreutz (2012), Abrupt change in atmospheric CO2 during the last ice age, Geophys. Res. Lett., doi:10.1029/2012GL053018.
Reduction of coal burning might lead to rapid near-term warming due to decrease in aerosol cooling
Aerosol contribution to the rapid warming of near-term climate under RCP 2.6 - Chalmers et al. (2012) [FULL TEXT]
Abstract: "The importance of aerosol emissions for near term climate projections is investigated by analysing simulations with the HadGEM2-ES model under two different emissions scenarios: RCP2.6 and RCP4.5. It is shown that the near term warming projected under RCP2.6 is greater than under RCP4.5, even though the greenhouse gas forcing is lower. Rapid and substantial reductions in sulphate aerosol emissions due to a reduction of coal burning in RCP2.6 lead to a reduction in the negative shortwave forcing due to aerosol direct and indirect effects. Indirect effects play an important role over the northern hemisphere oceans, especially the subtropical northeastern Pacific where an anomaly of 5-10\,Wm$^{-2}$ develops. The pattern of surface temperature change is consistent with the expected response to this surface radiation anomaly, whilst also exhibiting features that reflect redistribution of energy, and feedbacks, within the climate system. These results demonstrate the importance of aerosol emissions as a key source of uncertainty in near term projections of global and regional climate."
Citation: Chalmers, N., E. J. Highwood, E. Hawkins, R. T. Sutton, and L. J. Wilcox (2012), Aerosol contribution to the rapid warming of near-term climate under RCP 2.6, Geophys. Res. Lett., doi:10.1029/2012GL052848.
Coastal heat waves are projected to intensify relative to background warming in California
California heat waves in the present and future - Gershunov & Guirguis (2012)
Abstract: "Current and projected heat waves are examined over California and its sub-regions in observations and downscaled global climate model (GCM) simulations. California heat wave activity falls into two distinct types: (1) typically dry daytime heat waves and (2) humid nighttime-accentuated events (Type I and Type II, respectively). The four GCMs considered project Type II heat waves to intensify more with climate change than the historically characteristic Type I events, although both types are projected to increase. This trend is already clearly observed and simulated to various degrees over all sub-regions of California. Part of the intensification in heat wave activity is due directly to mean warming. However, when one considers non-stationarity in daily temperature variance, desert heat waves are expected to become progressively and relatively less intense while coastal heat waves are projected to intensify even relative to the background warming. This result generally holds for both types of heat waves across models. Given the high coastal population density and low acclimatization to heat, especially humid heat, this trend bodes ill for coastal communities, jeopardizing public health and stressing energy resources."
Citation: Gershunov, A. and K. Guirguis (2012), California heat waves in the present and future, Geophys. Res. Lett., doi:10.1029/2012GL052979.
Melt ponds on Arctic sea ice are important to include to model simulations
Impact of melt ponds on Arctic sea ice simulations from 1990 to 2007 - Flocco et al. (2012)
Abstract: "The extent and thickness of the Arctic sea ice cover has decreased dramatically in the past few decades with minima in sea ice extent in September 2007 and 2011 and climate models did not predict this decline. One of the processes poorly represented in sea ice models is the formation and evolution of melt ponds. Melt ponds form on Arctic sea ice during the melting season and their presence affects the heat and mass balances of the ice cover, mainly by decreasing the value of the surface albedo by up to 20%. We have developed a melt pond model suitable for forecasting the presence of melt ponds based on sea ice conditions. This model has been incorporated into the Los Alamos CICE sea ice model, the sea ice component of several IPCC climate models. Simulations for the period 1990 to 2007 are in good agreement with observed ice concentration. In comparison to simulations without ponds, the September ice volume is nearly 40 % lower. Sensitivity studies within the range of uncertainty reveal that, of the parameters pertinent to the present melt pond parameterization and for our prescribed atmospheric and oceanic forcing, variations of optical properties and the amount of snowfall have the strongest impact on sea ice extent and volume. We conclude that melt ponds will play an increasingly important role in the melting of the Arctic ice cover and their incorporation in the sea ice component of Global Circulation Models is essential for accurate future sea ice forecasts."
Citation: Flocco, D., D. Schroeder, D. L. Feltham, and E. C. Hunke (2012), Impact of melt ponds on Arctic sea ice simulations from 1990 to 2007, J. Geophys. Res., doi:10.1029/2012JC008195.
Also diurnal temperature range angle of cosmic rays is irrelevant for climate, try again
Examining a solar-climate link in diurnal temperature ranges - Laken et al. (2012) [FULL TEXT]
Abstract: "A recent study has suggested a link between the surface level diurnal temperature range (DTR) and variations in the cosmic ray (CR) flux. As the DTR is an effective proxy for cloud cover, this result supports the notion that widespread cloud changes may be induced by the CR flux. If confirmed, this would have significant implications for our understanding of natural climate forcings. Here, we perform a detailed investigation of the relationships between DTR and solar activity (total solar irradiance and the CR flux) from more than 60 years of NCEP/NCAR reanalysis data and observations from meteorological station data. We find no statistically significant evidence to suggest that the DTR is connected to either long-term solar periodicities (11 or 1.68-year) or short-term (daily timescale) fluctuations in solar activity, and we attribute previous reports on the contrary to an incorrect estimation of the statistical significance of the data. If a CR–DTR relationship exists, based on the estimated noise in DTR composites during Forbush decrease (FD) events, the DTR response would need to be larger than 0.03°C per 1% increase in the CR flux to be reliably detected. Compared with a much smaller rough estimate of −0.005°C per 1% increase in the CR flux expected if previous claims that FD events cause reductions in the cloud cover are valid, we conclude it is not possible to detect a solar related responses in station-based or reanalysis-based DTR data sets related to a hypothesized CR–cloud link, as potential signals would be drowned in noise."
Citation: Laken, B., J. ?alogovi?, T. Shahbaz, and E. Pallé (2012), Examining a solar-climate link in diurnal temperature ranges, J. Geophys. Res., 117, D18112, doi:10.1029/2012JD017683.
Scots pine forest is turning into oak forest in Swiss Rhone valley
Abstract: "An increasing number of studies have reported on forest declines and vegetation shifts triggered by drought. In the Swiss Rhone valley (Valais), one of the driest inner-Alpine regions, the species composition in low-elevation forests is changing: The sub-boreal Scots pine (Pinus sylvestris L.) dominating the dry forests is showing high mortality rates. Concurrently the sub-Mediterranean pubescent oak (Quercus pubescens Willd.) has locally increased in abundance. However, it remains unclear whether this local change in species composition is part of a larger-scale vegetation shift. To study variability in mortality and regeneration in these dry forests we analyzed data from the Swiss National Forest Inventory (NFI) on a regular grid between 1983 and 2003, and combined it with annual mortality data from a monitoring site. Pine mortality was found to be highest at low elevation (below 1000 m a.s.l.). Annual variation in pine mortality was correlated with a drought index computed for the summer months prior to observed tree death. A generalized linear mixed-effects model indicated for the NFI data increased pine mortality on dryer sites with high stand competition, particularly for small-diameter trees. Pine regeneration was low in comparison to its occurrence in the overstorey, while oak regeneration was comparably abundant. While both species regenerated well at dry sites, pine regeneration was favoured at cooler sites at higher altitude and oak regeneration was more frequent at warmer sites, indicating a higher adaptation potential of oaks under future warming. Our results thus suggest that an extended shift in species composition is actually occuring in the pine forests in the Valais. The main driving factors are found to be climatic variability, particularly drought, and variability in stand structure and topography. Thus, pine forests at low elevations are developing into oak forests with unknown consequences for these ecosystems and their goods and services."
Citation: A. Rigling, C. Bigler, B. Eilmann, E. Feldmeyer-Christe, U. Gimmi, C. Ginzler, U. Graf, P. Mayer, G. Vacchiano, P. Weber, T. Wohlgemuth, R. Zweifel, M. Dobbertin, Global Change Biology, DOI: 10.1111/gcb.12038.
NAO state generally coincides with Northern Hemisphere climate but during MWP there were no notable changes in NAO
Variability of the North Atlantic Oscillation over the past 5,200 years - Olsen et al. (2012)
Abstract: "Climate in the Arctic region and northwestern Europe is strongly affected by the North Atlantic Oscillation (NAO), the dominant mode of atmospheric variability at mid-latitudes in the North Atlantic region. The NAO index is an indicator of atmospheric circulation and weather patterns: when the index is positive, Europe and the eastern US are mild and wet, whereas Greenland and northern Canada are cold and dry. A negative index is associated with the reverse pattern. Reconstructions of the NAO have so far been limited to the past 900 years3. Here we analyse a 5,200-year-long, high-resolution lake sediment record from southwestern Greenland to reconstruct lake hypolimnic anoxia, and link the results to an existing reconstruction of the NAO index from tree rings and speleothems3. Using the relationship between the two records, we find that around 4,500 and 650 years ago—around the end of the Holocene Thermal Maximum and the beginning of the Little Ice Age, respectively—the NAO changed from generally positive to variable, intermittently negative conditions. We suggest that variability in the dominant state of the NAO tend to coincide with large-scale changes in Northern Hemisphere climate. However, the onset of the Medieval Climate Anomaly was not associated with any notable changes in the NAO."
Citation: Jesper Olsen, N. John Anderson, & Mads F. Knudsen, Nature Geoscience(2012), doi:10.1038/ngeo1589.
Nigerian farmers have noticed changes in climate and adjusted their farming practices to adapt
Abstract: "The savanna region of Africa is a potential breadbasket of the continent but is severely affected by climate change. Understanding farmers’ perceptions of climate change and the types of adjustments they have made in their farming practices in response to these changes will offer some insights into necessary interventions to ensure a successful adaptation in the region. This paper explores how smallholder farmers in the Nigerian savanna perceive and adapt to climate change. It is based on a field survey carried out among 200 smallholder farm households selected from two agro-ecological zones. The results show that most of the farmers have noticed changes in climate and have consequently adjusted their farming practices to adapt. There are no large differences in the adaptation practices across the region, but farmers in Sudan savanna agro-ecological zone are more likely to adapt to changes in temperature than those in northern Guinea savanna. The main adaptation methods include varying planting dates, use of drought tolerant and early maturing varieties and tree planting. Some of the farmers are facing limitations in adapting because of lack of information on climate change and the suitable adaptation measures and lack of credit. The study then concludes that to ensure successful adaptation to climate change in the region, concerted efforts are needed to design and promote planned adaptation measures that fit into the local context and also to educate farmers on climate change and appropriate adaptation measures."
Citation: Justice Akpene Tambo and Tahirou Abdoulaye, Regional Environmental Change, 2012, DOI: 10.1007/s10113-012-0351-0.
Other papers from last week
Did the Arctic ice recover? Demographics of true and false climate facts - Hamilton (2012)
Visibility trends in Tehran during 1958–2008 - Sabetghadam et al. (2012)
Soil carbon in the Arctic and the permafrost carbon feedback - van Huissteden & Dolman (2012)
Uncertainties in the global temperature change caused by carbon release from permafrost thawing - Burke et al. (2012) [FULL TEXT]
An integrated flask sample collection system for greenhouse gas measurements - Turnbull et al. (2012) [FULL TEXT]
A sea ice free summer Arctic within 30 years: An update from CMIP5 models - Wang & Overland (2012)
Can we predict the duration of an interglacial? - Txedakis et al. (2012) [FULL TEXT]
Past millennial solar forcing magnitude - A statistical hemispheric-scale climate model versus proxy data comparison - Hind & Moberg (2012) [FULL TEXT]
CLASSIC OF THE WEEK: Malmfors (1949)
Recordinds of Cosmic Radiation - Malmfors (2012) [FULL TEXT]
Abstract: "The main purpose of the registrations reported here has been to study the diurnal variations of C. R. and especially to investigate how the amplitude and the phase of the variation depend on the direction of incidence. Since statistical fluctuations will dominate over the significant ones unless a sufficiently large number of coincidences is counted, it has been necessary to use an apparatus with a high counting speed. C. R. has been recorded continuously in Stockholm (magn. lat. 58°) since 1. 10. 1947 by means of large counters in coincidence circuit. Recordings have been made in three different directions simultaneously, and the total number of particles counted amounts to 109. The material has been analyzed with respect to diurnal variation. This analysis definitely proves that the variation is not the same in different directions. A term called C. R. activity has been introduced for the purpose of classifying the registrations according to the magnitude of the variation for each day. An analysis shows that large activity is very often observed during consecutive days."
Citation: K. G. Malmfors, Tellus, Volume 1, Issue 2, pages 55–61, May 1949, DOI: 10.1111/j.2153-3490.1949.tb01259.x.
This is a cross-post from AGW Observer. 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. 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.
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