AGW Observer

Observations of anthropogenic global warming

New research from last week 44/2011

Posted by Ari Jokimäki on November 7, 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.

Fish parasites grow faster in warmer water

Some (worms) like it hot: fish parasites grow faster in warmer water, and alter host thermal preferences – Macnab & Barber (2011) “Elevated environmental temperatures associated with anthropogenic warming have the potential to impact host-parasite interactions, with consequences for population health and ecosystem functioning. One way that elevated temperatures might influence parasite prevalence and intensity is by increasing life cycle completion rates. Here we investigate how elevated temperatures impact a critical phase of the life cycle of the bird tapeworm Schistocephalus solidus – the growth of plerocercoid larvae in host sticklebacks Gasterosteus aculeatus. By 8 weeks post-infection, plerocercoids recovered from experimentally infected sticklebacks held at 20C weighed on average 104.9mg, with all exceeding 50mg, the mass considered consistently infective to definitive hosts. In contrast, plerocercoids from sticklebacks held at 15C weighed on average 26.5mg, with none exceeding 50mg. Because small increases in plerocercoid mass affect adult fecundity disproportionately in this species, enhanced plerocercoid growth at higher temperatures predicts dramatically increased output of infective parasite stages. Subsequent screening of thermal preferences of sticklebacks from a population with endemic S. solidus infection demonstrated that fish harbouring infective plerocercoids show significant preferences for warmer temperatures. Our results therefore indicate that parasite transmission might be affected in at least two ways under anthropogenic warming; by enhancing rates of parasite growth and development, and by increasing the likelihood of hosts being able to seek out proliferating warmer microhabitats. Furthermore, our results suggest the potential for positive feedback between parasite growth and host thermal preferences, which could dramatically increase the effects of even small temperature increases. We discuss the possible mechanisms underpinning our results, their likely ecological consequences and highlight key areas for further research.” Vicki Macnab, Iain Barber, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02595.x.

Knutti & Plattner comment on Schwartz et al. 2010

Comment on “Why Hasn’t Earth Warmed as Much as Expected?” by Schwartz et al. 2010 – Knutti & Plattner (2011) “In a recent paper, Schwartz et al. suggest that (1) over the last century the Earth has warmed less than expected, and they discuss several factors that could explain the discrepancy, including climate sensitivity estimates and aerosol forcing. Schwartz et al. then continue to (2) estimate the allowed carbon emissions for stabilization of global temperature, and find that given the uncertainty in the climate sensitivity even the sign of these allowed carbon emissions is unknown, implying that past emissions may already have committee the Earth to two degrees warming for a best estimate value of climate sensitivity of 3 K. We take issue with both of these conclusions in the Schwartz et al. study and show here that (1) in contrast to Schwartz et al., current assessments of climate sensitivity, radiative forcing and thermal disequilibrium do not support the claim of a discrepancy between expected and observed warming; and (2) the allowed emissions estimated by Schwartz et al. are in conflict with results from a hierarchy of climate-carbon cycle models and strongly underestimated due to erroneous assumptions about the behavior of the carbon cycle and a confusion of the relevant timescales.” Reto Knutti and Gian-Kasper Plattner, Journal of Climate 2011, doi: 10.1175/2011JCLI4038.1.

Link to Schwartz et al. reply (no abstract or full text freely available).

Central Siberia agriculture would likely benefit from climate warming

Agroclimatic potential across central Siberia in an altered twenty-first century – Tchebakova et al. (2011) “Humans have traditionally cultivated steppe and forest-steppe on fertile soils for agriculture. Forests are predicted to shift northwards in a warmer climate and are likely to be replaced by forest-steppe and steppe ecosystems. We analyzed potential climate change impacts on agriculture in south-central Siberia believing that agriculture in traditionally cold Siberia may benefit from warming. Simple models determining crop range and regression models determining crop yields were constructed and applied to climate change scenarios for various time frames: pre-1960, 1960–90 and 1990–2010 using historic data and data taken from 2020 and 2080 HadCM3 B1 and A2 scenarios. From 50 to 85% of central Siberia is predicted to be climatically suitable for agriculture by the end of the century, and only soil potential would limit crop advance and expansion to the north. Crop production could increase twofold. Future Siberian climatic resources could provide the potential for a great variety of crops to grow that previously did not exist on these lands. Traditional Siberian crops could gradually shift as far as 500 km northwards (about 50–70 km/decade) within suitable soil conditions, and new crops nonexistent today may be introduced in the dry south that would necessitate irrigation. Agriculture in central Siberia would likely benefit from climate warming. Adaptation measures would sustain and promote food security in a warmer Siberia.” N M Tchebakova et al 2011 Environ. Res. Lett. 6 045207 doi:10.1088/1748-9326/6/4/045207. [Full text]

Handling uncertainty in science – Philosophical Transactions A special issue

Discussion Meeting Issue ‘Handling uncertainty in science’ organized and edited by T. N. Palmer and P. J. Hardaker – Palmer et al. (2011) “Despite this key role of uncertainty in science, there have been few meetings where working scientists from different disciplines have come together to discuss and compare the methods by which they handle and communicate uncertainty. The Discussion Meeting at the Royal Society on 22-23 March 2010,on which this issue is based, afforded a unique opportunity for such a discussion and comparison. Indeed, this may have been one of the most interdisciplinary Royal Society Discussion Meetings for quite some time, with participation from leaders in the fields of theoretical physics, statistics, philosophy, mathematics, cosmology, health, economics, climate, as well as from the media, government and business. Whether it is in guiding efforts to progress our knowledge and understanding of science, or in developing procedures for rational decision making, or in communicating our science to others, there is much that scientists can learn from one another in developing methodologies to handle uncertainty. It is therefore important that, from time to time, scientists come together to communicate across their disciplinary boundaries, and share experience and expertise in handling this key aspect of the scientific method. The 2010 Discussion Meeting and this collection of papers provides an unrivalled opportunity to do just this. It is hoped that more will follow.” Philosophical Transactions A, December 13, 2011; 369 (1956). [Issue contains some open access papers]

Full text of ‘Uncertainty in weather and climate prediction’ by Slingo & Palmer

Malaria occurrance linked to temperature in Colombia

Integrating knowledge and management regarding the climate–malaria linkages in Colombia – Poveda et al. (2011) “Malaria is a complex multi-factorial disease whose outcomes are affected by climate and environmental variability. In particular, malaria is endemic in the year-round hot and humid lowlands of Colombia, whose hydro-climatology exhibits clear-cut variability at interannual timescales, mostly driven by both phases of El Niño/Southern Oscillation (ENSO): El Niño (warm phase) and La Niña (cold phase). Here we show highly significant statistical correlations between malaria outbreaks in Colombia during historical El Niño events of 1959–2009. Analyses are performed at national, regional, and municipal spatial scales, and at annual, quarterly, and monthly timescales. Annual malaria incidence in Colombia exhibits a combination of long-term trends (which might be explained by historical increasing trends in average air temperatures throughout Colombia, in turn owing to global warming and deforestation), as well as strong malaria outbreaks during El Niño, as a consequence of the concomitant increases in air temperature. Also, we show that satellite imagery of vegetation activity can be used as an environmental indicator for malaria in Colombia. We discuss how these research results and diverse knowledge-based tools, including mathematical explanatory models and geographical information systems, are being used by the Colombian health authorities as an end-to-end program and early warning system (EWS) for malaria prevention and surveillance countrywide.” Germán Poveda, Óscar A Estrada-Restrepo, Julián E Morales, Ólver O Hernández, Armando Galeano, Salua Osorio, Current Opinion in Environmental Sustainability, doi:10.1016/j.cosust.2011.10.004.

Regeneration potential decreases for some and increases for some eucalypt species

Modelling the potential impact of climate variability and change on species regeneration potential in the temperate forests of South-Eastern Australia – Mok et al. (2011) “The sensitivity of early plant regeneration to environmental change makes regeneration a critical stage for understanding species response to climate change. We investigated the spatial and temporal response of eucalypt trees in the Central Highland region of south eastern Australia to high and low climate change scenarios. We developed a novel mechanistic model incorporating germination processes, TACA-GEM, to evaluate establishment probabilities of five key eucalypt species, Eucalyptus pauciflora, E. delegatensis, E. regnans, E. nitens, and E. obliqua. Changes to regeneration potential at landscape and site levels were calculated to determine climate thresholds. Model results demonstrated that climate change is likely to impact on plant regeneration. We observed increases and decreases of regeneration potential depending on the ecosystem, indicating that some species will increase in abundance in some forest types whilst other forest types will become inhabitable. In general the dry forest ecosystems were most impacted whilst the wet forests were least impacted. We also observed that species with seed dormancy mechanisms, like E. pauciflora and E. delegatensis, are likely to be at higher risk than those without. Landscape and site level analysis revealed heterogeneity in species response at different scales. On a landscape scale, a 4.3°C mean temperature increase and 22% decline in precipitation (predicted for 2080) is predicted to be a threshold for large spatial shifts in species regeneration niches across the study region, while a 2.6°C increase and 15% decline in precipitation (predicted for 2050) will likely result in local site-level shifts. Site-level analysis showed that considerable declines in regeneration potential for E. delegatensis, E. pauciflora, and E. nitens were modelled to occur in some ecosystems by 2050. While overall model performance and accuracy was good, better understanding of effects from extreme events and other underlying processes on regeneration will improve modelling and development of species conservation strategies.” Hoi-Fei Mok, Craig R. Nitschke, Stefan K. Arndt, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02591.x.

Interdependency of aerosol forcing and climate sensitivity increases the uncertainty of projections

Correlation between climate sensitivity and aerosol forcing and its implication for the “climate trap” – Tanaka & Raddatz (2011) “Climate sensitivity and aerosol forcing are dominant uncertain properties of the global climate system. Their estimates based on the inverse approach are interdependent as historical temperature records constrain possible combinations. Nevertheless, many literature projections of future climate are based on the probability density of climate sensitivity and an independent aerosol forcing without considering the interdependency of such estimates. Here we investigate how large such parameter interdependency affects the range of future warming in two distinct settings: one following the A1B emission scenario till the year 2100 and the other assuming a shutdown of all greenhouse gas and aerosol emissions in the year 2020. We demonstrate that the range of projected warming decreases in the former case, but considerably broadens in the latter case, if the correlation between climate sensitivity and aerosol forcing is taken into account. Our conceptual study suggests that, unless the interdependency between the climate sensitivity and aerosol forcing estimates is properly considered, one could underestimate a risk involving the “climate trap”, an unpalatable situation with a high climate sensitivity in which a very drastic mitigation may counter-intuitively accelerate the warming by unmasking the hidden warming due to aerosols.” Katsumasa Tanaka and Thomas Raddatz, Climatic Change, DOI: 10.1007/s10584-011-0323-2.

DeVries cycle of solar activity shows in tree-ring chronologies

Solar and volcanic fingerprints in tree-ring chronologies over the past 2000 years – Breitenmoser et al. (2011) “The Sun is the main driver of Earth’s climate, yet the Sun’s role in forcing decadal-to-centennial climate variations has remained controversial, especially in the context of understanding contributions of natural climate forcings to continuing global warming. To properly address long-term fingerprints of solar forcing on climate, long-term, very high-resolution, globally distributed climate proxy records are necessary. In this study we compile and evaluate a near global collection of annually-resolved tree-ring-based climate proxies spanning the past two millennia. We statistically assess these records in both the time and frequency domains for solar forcing (i.e. Total Solar Irradiance; TSI) and climate variability with emphasis on centennial time scales. Analyses in the frequency domain indicate significant periodicities in the 208-year frequency band, corresponding to the DeVries cycle of solar activity. Additionally, results from superposed epoch analysis (SEA) point toward a possible solar contribution in the temperature and precipitation series. However, solar-climate associations remain weak, with for example no clear linkage distinguishable in the southwestern United States drought records at centennial time scales. Other forcing factors, namely volcanic activity, appear to mask the solar signal in space and time. To investigate this hypothesis, we attempted to extract volcanic signals from the temperature proxies using a statistical modelling approach. Wavelet analysis of the volcanic contribution reveals significant periodicities near the DeVries frequency during the Little Ice Age (LIA). This remarkable and coincidental superposition of the signals makes it very difficult to separate volcanic and solar forcing during the LIA. Nevertheless, the “volcano free” temperature records show significant periodicities near the DeVries periodicity during the entire past 1500 years, further pointing to solar mechanisms and emphasising the need for solar related studies in the absence of strong multi-decadal volcanic forcing.” Petra Breitenmoser, Jürg Beer, Stefan Brönnimann, David Frank, Friedhelm Steinhilber, Heinz Wanner, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2011.10.014.

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