New research from last week 1/2011

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:

Forest fires expected to increase in Finland

Climate change impacts on forest fire potential in boreal conditions in Finland – Kilpeläinen et al. (2011) “The aim of this work was to study the forest fire potential and frequency of forest fires under the projected climate change in Finland (N 60°–N 70°). Forest fire index, generally utilized in Finland, was used as an indicator for forest fire potential due to climatological parameters. Climatic scenarios were based on the A2 emission scenario. According to the results, the forest fire potential will have increased by the end of this century; as a result of increased evaporative demand, which will increase more than the rise in precipitation and especially in southern Finland. The annual number of forest fire alarm days is expected to increase in southern Finland to 96–160 days by the end of this century, compared to the current 60–100 days. In the north, the corresponding increase was from 30 to 36 days. The expected increase in the annual frequency of forest fires over the whole country was about 20% by the end of this century compared to the present day. The greatest increase in the frequency of fires, per 1,000 km², was in the southernmost part of the country, with six to nine fires expected annually per 1,000 km² at the end of this century, meaning a 24–29% increase compared to the present day frequencies.” Antti Kilpeläinen, Seppo Kellomäki, Harri Strandman and Ari Venäläinen, Climatic Change, Volume 103, Numbers 3-4, 383-398, DOI: 10.1007/s10584-009-9788-7.

Adaptation has already saved lives in England

Causes for the recent changes in cold- and heat-related mortality in England and Wales – Christidis et al. (2011) “Cold related mortality among people aged over 50 in England and Wales has decreased at a rate of 85 deaths per million population per year over the period 1976–2005. This trend is two orders of magnitude higher than the increase in heat-related mortality observed after 1976. Long term changes in temperature-related mortality may be linked to human activity, natural climatic forcings, or to adaptation of the population to a wider range of temperatures. Here we employ optimal detection, a formal statistical methodology, to carry out an end to end attribution analysis. We find that adaptation is a major influence on changing mortality rates. We also find that adaptation has prevented a significant increase in heat-related mortality and considerably enhanced a significant decrease in cold-related mortality. Our analysis suggests that in the absence of adaptation, the human influence on climate would have been the main contributor to increases in heat-related mortality and decreases in cold-related mortality.” Nikolaos Christidis, Gavin C. Donaldson and Peter A. Stott, Climatic Change, Volume 102, Numbers 3-4, 539-553, DOI: 10.1007/s10584-009-9774-0. [conference article]

Iron fertilization not effective in mitigating ocean acidification

Can ocean iron fertilization mitigate ocean acidification? – Cao & Caldeira (2011) “Ocean iron fertilization has been proposed as a method to mitigate anthropogenic climate change, and there is continued commercial interest in using iron fertilization to generate carbon credits. It has been further speculated that ocean iron fertilization could help mitigate ocean acidification. Here, using a global ocean carbon cycle model, we performed idealized ocean iron fertilization simulations to place an upper bound on the effect of iron fertilization on atmospheric CO2 and ocean acidification. Under the IPCC A2 CO2 emission scenario, at year 2100 the model simulates an atmospheric CO2 concentration of 965 ppm with the mean surface ocean pH 0.44 units less than its pre-industrial value of 8.18. A globally sustained ocean iron fertilization could not diminish CO2 concentrations below 833 ppm or reduce the mean surface ocean pH change to less than 0.38 units. This maximum of 0.06 unit mitigation in surface pH change by the end of this century is achieved at the cost of storing more anthropogenic CO2 in the ocean interior, furthering acidifying the deep-ocean. If the amount of net carbon storage in the deep ocean by iron fertilization produces an equivalent amount of emission credits, ocean iron fertilization further acidifies the deep ocean without conferring any chemical benefit to the surface ocean.” Long Cao and Ken Caldeira, Climatic Change, Volume 99, Numbers 1-2, 303-311, DOI: 10.1007/s10584-010-9799-4. [full text]

European temperature records of the past five centuries

European temperature records of the past five centuries based on documentary/instrumental information compared to climate simulations – Zorita et al. (2011) “Two European temperature reconstructions for the past half-millennium, January-to-April air temperature for Stockholm (Sweden) and seasonal temperature for a Central European region, both derived from the analysis of documentary sources and long instrumental records, are compared with the output of climate simulations with the model ECHO-G. The analysis is complemented by comparisons with the long (early)-instrumental record of Central England Temperature (CET). Both approaches to study past climates (simulations and reconstructions) are burdened with uncertainties. The main objective of this comparative analysis is to identify robust features and weaknesses in each method which may help to improve models and reconstruction methods. The results indicate a general agreement between simulations obtained with temporally changing external forcings and the reconstructed Stockholm and CET records for the multi-centennial temperature trend over the recent centuries, which is not reproduced in a control simulation. This trend is likely due to the long-term change in external forcing. Additionally, the Stockholm reconstruction and the CET record also show a clear multi-decadal warm episode peaking around AD 1730, which is absent in the simulations. Neither the reconstruction uncertainties nor the model internal climate variability can easily explain this difference. Regarding the interannual variability, the Stockholm series displays, in some periods, higher amplitudes than the simulations but these differences are within the statistical uncertainty and further decrease if output from a regional model driven by the global model is used. The long-term trend of the CET series agrees less well with the simulations. The reconstructed temperature displays, for all seasons, a smaller difference between the present climate and past centuries than is seen in the simulations. Possible reasons for these differences may be related to a limitation of the traditional ‘indexing’ technique for converting documentary evidence to temperature values to capture long-term climate changes, because the documents often reflect temperatures relative to the contemporary authors’ own perception of what constituted ‘normal’ conditions. By contrast, the amplitude of the simulated and reconstructed inter-annual variability agrees rather well.” Eduardo Zorita, Anders Moberg, Lotta Leijonhufvud, Rob Wilson, Rudolf Brázdil, Petr Dobrovolný, Jürg Luterbacher, Reinhard Böhm, Christian Pfister and Dirk Riemann, et al., Climatic Change, Volume 101, Numbers 1-2, 143-168, DOI: 10.1007/s10584-010-9824-7. [conference presentation]

Link between Tibetan Plateau snow cover and North American winter temperature

Contribution of the autumn Tibetan Plateau snow cover to seasonal prediction of North American winter temperature – Lin & Wu (2011) “Predicting surface air temperature (Ts) is a major task of North American (NA) winter seasonal prediction. It has been recognized that variations of the NA winter Ts can be associated with El Niño–Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). This study presents observed evidence that variability in snow cover over the Tibetan Plateau (TP) and its adjacent areas in prior autumn (September–November) is significantly correlated with the first principal component (PC1) of the NA winter Ts which features a meridional seesaw pattern over the NA continent. The autumn TP snow cover anomaly can persist into the following winter through a positive feedback between snow cover and the atmosphere. A positive TP snow cover anomaly may induce a negative sea level pressure and geopotential height anomaly over the eastern North Pacific, a positive geopotential height anomaly over Canada, and a negative anomaly over southeast US, a structure very similar to the positive phase of the Pacific-North American (PNA) pattern. This usually favors the occurrence of a warm-North-cold-South winter over the NA continent. When a negative snow cover anomaly occurs, the situation tends to be opposite. Since the autumn TP snow cover shows a weak correlation with ENSO, it provides a new predictability source for NA winter Ts. Based on the above results, an empirical model is constructed to predict PC1 by a combination of autumn TP snow cover and other sea surface temperature anomalies related to ENSO and the NAO. Hindcasts and real forecasts are performed for the 1972–2003 and 2004–2009 periods, respectively. Both show a promising prediction skill. As far as PC1 is concerned, the empirical model hindcast performs better than the ensemble mean of four dynamical models from the Canadian Meteorological Center. Particularly, the real forecast of the empirical model exhibits a better performance in predicting the extreme phases of PC1, i.e., the extremely warm winter over Canada in 2009/2010, should the model include the autumn TP snow cover impacts. Since all these predictors can be readily monitored in real time, this empirical model provides a real time forecast tool for NA winter climate.” Hai Lin and Zhiwei Wu, Journal of Climate, 2011.

Linear trend not best way to describe long term SST trends

Testing for deterministic trends in global sea surface temperature – Barbosa (2011) “Long-term variability in global sea surface temperature (SST) is often quantified by the slope from a linear regression fit. Attention is then focused on assessing the statistical significance of the derived slope parameter, but the adequacy of the linear model itself, and the inherent assumption of a deterministic linear trend, is seldom tested. Here, a parametric statistical test is applied to test the hypothesis of a linear deterministic trend in global sea surface temperature. The results show that a linear slope is not adequate for describing the long-term variability of sea surface temperature over most of the Earth’s surface. This doesn’t mean that sea surface temperature is not increasing, rather that the increase shouldn’t be characterized by the slope from a linear fit. Therefore, describing the long-term variability of sea surface temperature by implicitly assuming a deterministic linear trend can give misleading results, particularly in terms of uncertainty, since the actual increase could be considerably larger than the one predicted by a deterministic linear model.” Susana M. Barbosa, Journal of Climate, 2011.

Lake in Germany shows human impact 1000s of years ago

Climate change and human impact at Sacrower See (NE Germany) during the past 13,000 years: a geochemical record – Enters et al. (2011) “Lacustrine sediments in north-eastern Germany have rarely been used as archives to address the effects of climate change and human impact on both lake ecosystem and landscape evolution for this region. Sacrower See, a hardwater lake located in Brandenburg, provides a unique sediment record covering the past 13,000 years which was used to reconstruct climatic and anthropogenic forcing on lacustrine sedimentation. Time control is provided by 12 AMS ¹⁴C dates of terrestrial plant remains, the Laacher See Tephra, and the onset of varve formation in AD 1870 (80 cal. BP). Geochemical (including XRF logging of major elements, CNS analyses as well as δ¹³Corg and δ¹⁵N measurements) and pollen analyses allowed detecting detailed environmental changes in the sediment record. During the Younger Dryas cold phase increased soil erosion and hypolimnetic oxygen depletion enhanced the nutrient supply to the lake water causing eutrophic conditions. The beginning of the Holocene is characterized by large changes in C/N ratios, total sulphur, δ¹³C of bulk organic matter as well as in K, Si, and Ti, reflecting the response of the lake’s catchment to climatic warming. Reforestation reduced the influx of detrital particles and terrestrial organic matter. The first, rather weak evidence of human impact is documented only in the pollen record at 5,500 cal. BP. However, until 3,200 cal. BP sedimentological and geochemical parameters indicate relatively stable environmental conditions. During periods of intense human impact at around 3,200, 2,800, and 900 cal. BP peaks in Ti and K represent phases of increased soil erosion due to forest clearing during the Bronze Age, Iron Age, and Medieval Times, respectively. In general, greater variation is observed in most variables during these perturbations, indicating less stable environmental conditions. The steady rise of biogenic silica accumulation rates during the Holocene reflects an increasing productivity of Sacrower See until diatoms were outcompeted by other algae during the last centuries. The applied multi-proxy approach fosters the interpretation of the sediment record to reveal a consistent picture of environmental change including environmental factors controlling lake ontogeny and the effects of human impact.” D. Enters, E. Kirilova, A. F. Lotter, A. Lücke, J. Parplies, S. Jahns, G. Kuhn and B. Zolitschka, Journal of Paleolimnology, Volume 43, Number 4, 719-737, DOI: 10.1007/s10933-009-9362-3.

Climate effect of volcanoes depend on time of the year

Climate effects of high-latitude volcanic eruptions: Role of the time of year – Kravitz & Robock (2011) “We test how the time of year of a large Arctic volcanic eruption determines the climate impacts by conducting simulations with a general circulation model of Earth’s climate. For eruptions injecting less than about 3 Tg of SO₂ into the lower stratosphere, we expect no detectable climatic effect, no matter what the season of the eruption. For an injection of 5 Tg of SO₂ into the lower stratosphere, an eruption in the summer would cause detectable climate effects, whereas an eruption at other times of the year would cause negligible effects. This is mainly due to the seasonal variation in insolation patterns and sulfate aerosol deposition rates. In all cases, the sulfate aerosols that form get removed from the atmosphere within a year after the eruption by large-scale deposition. Our simulations of a June eruption have many similar features to previous simulations of the eruption of Katmai in 1912, including some amount of cooling over Northern Hemisphere continents in the summer of the eruption, which is an expected climate response to large eruptions. Previous Katmai simulations show a stronger climate response, which we attribute to differences in choices of climate model configurations, including their specification of sea surface temperatures rather than the use of a dynamic ocean model as in the current simulations.” Kravitz, B., and A. Robock (2011), J. Geophys. Res., 116, D01105, doi:10.1029/2010JD014448. [full text]

Atmosphere’s self-cleaning capacity is rather stable

NOAA news release

SPESTMW increases under global warming

Increase of South Pacific eastern subtropical mode water under global warming – Luo et al. (2011) “The response of South Pacific Eastern Subtropical Mode Water (SPESTMW) to global warming is investigated by comparing solutions from a set of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) coupled models between a present-day climate and a future, warmer climate. Under the warmer climate scenario, the SPESTMW extends southwestward and is significantly increased in volume. This is because all the local surface forcing mechanisms (i.e., wind stress, heat and freshwater fluxes) in the eastern subtropical South Pacific tends to de-stratify the upper ocean and thus deepen the mixed layer. Further, a suite of process-oriented experiments with an ocean general circulation model suggest that it is the intensified southeast trade winds under the warmer climate that promotes more heat flux from the ocean into the atmosphere that then results in a deepening of the mixed layer in the eastern subtropics of the South Pacific.” Luo, Y., Q. Liu, and L. M. Rothstein (2011), Geophys. Res. Lett., 38, L01601, doi:10.1029/2010GL045878.

NAO relation to summer climate in Europe

A summer climate regime over Europe modulated by the North Atlantic Oscillation – Wang et al. (2011) “Recent summer heat waves in Europe were found to be preceded by precipitation deficits in winter. Numerical studies suggest that these phenomena are dynamically linked by land-atmosphere interactions. However, there exists as yet no complete observational evidence that connects summer climate variability to winter precipitation and the relevant circulation patterns. In this paper, we investigate the functional responses of summer mean and maximum temperature (June–August, T_mean and T_max) as well as soil moisture proxied by the self-calibrating Palmer drought severity index (scPDSI) to preceding winter precipitation (January–March, P_JFM) for the period 1901–2005. All the analyzed summer fields show distinctive responses to P_JFM over the Mediterranean. We estimate that 10 ~ 15% of the interannual variability of T_max and T_mean over the Mediterranean is statistically forced by P_JFM. For the scPDSI this amounts to 10 ~ 25%. Further analysis shows that these responses are highly correlated to the North Atlantic Oscillation (NAO) regime over the Mediterranean. We suggest that NAO modulates European summer temperature by controlling winter precipitation that initializes the moisture states that subsequently interact with temperature. This picture of relations between European summer climate and NAO as well as winter precipitation suggests potential for improved seasonal prediction of summer climate for particular extreme events.” Wang, G., Dolman, A. J., and Alessandri, A.: A summer climate regime over Europe modulated by the North Atlantic Oscillation, Hydrol. Earth Syst. Sci., 15, 57-64, doi:10.5194/hess-15-57-2011, 2011. [full text]

Studying Greenland ice sheet sliding with radar

Radar images of the bed of the Greenland Ice Sheet – Jezek et al. (2011) “In this paper, we apply radar tomography methods to very-high-frequency, airborne synthetic-aperture radar data to measure the ice thickness field and to construct three-dimensional basal image maps of a 5 × 20 km study area located along the southern flank of the Jakobshavn Glacier, Greenland. Unlike ice radar measurements typically made at nadir, our approach uses radar-echo phase and amplitude measured across an antenna array to determine the propagation angle and signal strength of pixel elements distributed on each side of the aircraft flight path. That information, combined with knowledge of aircraft position and the assumed dielectric properties of the glacier, can be used to measure ice thickness and radar reflectivity across a 3-km wide swath. Combining ice thickness and surface topography data, we estimate basal topography and basal drag. We conclude that the glacier is sliding over the bed. We use the three-dimensional image maps of the bed to inspect the modern subglacial geomorphology and find for the first time beneath the Greenland Ice Sheet assemblages of long ridge-groove landforms that are oriented in the direction of the ice flow. Spatial dimensions (10 to 30 m depths, 150 to 500 m spacing and lengths of 10 km or more) and correlation with the current ice flow direction suggest that these are glacial erosional features similar to mega-grooves observed on deglaciated terrain.” Jezek, K., X. Wu, P. Gogineni, E. Rodríguez, A. Freeman, F. Rodriguez-Morales, and C. D. Clark (2011), Geophys. Res. Lett., 38, L01501, doi:10.1029/2010GL045519.

Estimating global solar radiation

Statistical downscaling with Bayesian inference: Estimating global solar radiation from reanalysis and limited observed data – Iizumi et al. (2011) “Daily global solar radiation (SR) is one of essential weather inputs for crop, hydrological, and other simulation models to calculate biomass production and potential evapotranspiration. The availability of long-term observed SR data is, however, limited, especially in developing countries. This hinders climate applications in various sectors in these countries. To overcome this difficulty, we here propose a method to infer the reasonable daily SR condition for past decades from global reanalysis and limited observed SR data. The method consists of the regression-based statistical downscaling method and two empirical models for estimating the SR condition (i.e. the S-model and the DTR/RH-model). These empirical models were independent in terms of the variables explaining the SR condition. The regression models were trained on the basis of the SR conditions estimated by the S-model and the DTR/RH-model instead of the observed SR data. The Markov Chain Monte Carlo (MCMC) technique was applied to determine the parameter values of these models that guide the models to provide SR conditions that are close in value to each other at both the site and domain-mean scales. After that, we computed the SR condition over the 30 years from 1978 through 2007 at 17 sites in the Vietnam Mekong Delta area using the determined parameter values. The inferred SR condition was close in value to the corresponding observations available from the literature. This suggests that the proposed method yielded a reasonable inference of the SR condition at the sites despite the limited availability of observed SR data. The provided estimates of the daily SR condition over the past 30 years are useful for climate applications in agricultural, hydrological, and other sectors in this area.” Toshichika Iizumi, Motoki Nishimori, Masayuki Yokozawa, Akihiko Kotera, Nguyen Duy Khang, International Journal of Climatology, DOI: 10.1002/joc.2281.