Arctic tundra fires: natural variability and responses to climate change

2015 ◽  
Vol 13 (7) ◽  
pp. 369-377 ◽  
Author(s):  
Feng Sheng Hu ◽  
Philip E Higuera ◽  
Paul Duffy ◽  
Melissa L Chipman ◽  
Adrian V Rocha ◽  
...  
Keyword(s):  
Climate Change ◽  
Arctic Tundra ◽  
Natural Variability

scholarly journals Effect of environmental history on the habitat-forming kelp Macrocystis pyrifera responses to ocean acidification and warming: a physiological and molecular approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pamela A. Fernández ◽  
Jorge M. Navarro ◽  
Carolina Camus ◽  
Rodrigo Torres ◽  
Alejandro H. Buschmann
Keyword(s):  
Climate Change ◽  
Ocean Acidification ◽  
Environmental History ◽  
Coastal Upwelling ◽  
Macrocystis Pyrifera ◽  
Natural Variability ◽  
Kelp Forests ◽  
Species Response ◽  
Enhanced Expression ◽  
Mesocosm Experiments

AbstractThe capacity of marine organisms to adapt and/or acclimate to climate change might differ among distinct populations, depending on their local environmental history and phenotypic plasticity. Kelp forests create some of the most productive habitats in the world, but globally, many populations have been negatively impacted by multiple anthropogenic stressors. Here, we compare the physiological and molecular responses to ocean acidification (OA) and warming (OW) of two populations of the giant kelp Macrocystis pyrifera from distinct upwelling conditions (weak vs strong). Using laboratory mesocosm experiments, we found that juvenile Macrocystis sporophyte responses to OW and OA did not differ among populations: elevated temperature reduced growth while OA had no effect on growth and photosynthesis. However, we observed higher growth rates and NO3− assimilation, and enhanced expression of metabolic-genes involved in the NO3− and CO2 assimilation in individuals from the strong upwelling site. Our results suggest that despite no inter-population differences in response to OA and OW, intrinsic differences among populations might be related to their natural variability in CO2, NO3− and seawater temperatures driven by coastal upwelling. Further work including additional populations and fluctuating climate change conditions rather than static values are needed to precisely determine how natural variability in environmental conditions might influence a species’ response to climate change.

Evaluation of the daily cycle in the simulation of the ClimEx large-ensemble

2021 ◽  
Author(s):  
Anne-Marie Begin
Keyword(s):  
Climate Change ◽  
Estimation Error ◽  
Natural Variability ◽  
Extreme Weather Events ◽  
Large Ensemble ◽  
Daily Cycle ◽  
Minimum Number ◽  
The Mean ◽  
Mean Cycle ◽  
The Impact

<p>To estimate the impact of climate change on our society we need to use climate projections based on numerical models. These models make it possible to assess the effects on climate of the increase in greenhouse gases (GHG) as well as natural variability. We know that the global average temperature will increase and that the occurrence, intensity and spatio-temporal distribution of extreme precipitations will change. These extreme weather events cause droughts, floods and other natural disasters that have significant consequences on our life and environment. Precipitation is a key variable in adapting to climate change.</p><p> </p><p>This study focuses on the ClimEx large ensemble, a set of 50 independent simulations created to study the effect of climate change and natural variability on the water network in Quebec. This dataset consists of simulations produced using the Canadian Regional Climate Model version 5 (CRCM5) at 12 km of resolution driven by simulations from the second generation Canadian Earth System Model (CanESM2) global model at 310 km of resolution.</p><p> </p><p>The aim of the project is to evaluate the performance of the ClimEx ensemble in simulating the daily cycle and representing extreme values.  To get there, 30 years of hourly time series for precipitation and 3 hourly for temperature are analyzed. The simulations are compared with the values from the simulation of CRCM5 driven by ERA-Interim reanalysis, the ERA5 reanalysis and Environment and Climate Change Canada (ECCC) stations. An evaluation of the sensitivity of different statistics to the number of members is also performed.</p><p> </p><p>The daily cycle of precipitation from ClimEx shows mainly non-significant correlations with the other datasets and its amplitude is less than the observation datas from ECCC stations. For temperature, the correlation is strong and the amplitude of the cycle is similar to observations. ClimEx provides a fairly good representation of the 95, 97, 99<sup>th</sup> quantiles for precipitation. For temperature it represents a good distribution of quantiles but with a warm bias in southern Quebec. For precipitation hourly maximum, ClimEx shows values 10 times higher than ERA5.  For temperature, minimum and maximum values may exceed the ERA5 limit by up to 20°C. For precipitation, the minimum number of members for the estimation of the 95 and 99<sup>th</sup><sup></sup>quantiles and the mean cycle is between 15 and 50 for an estimation error of less than 5%. For the 95, 99<sup>th</sup> quantiles of temperature, the minimum number of members is between 1 and 17 and for the mean cycle 1 to 2 members are necessary to obtain an estimation error of less than 0.5°C.</p>

Nitrogen fixation beyond leguminous plants: characterising overlooked plant-bacteria associations in the light of climate change

2020 ◽  
Author(s):  
Kathrin Rousk
Keyword(s):  
Climate Change ◽  
Nitrogen Fixation ◽  
Community Composition ◽  
Abiotic Factors ◽  
Arctic Tundra ◽  
The Arctic ◽  
Mean Annual Precipitation ◽  
Precipitation Gradient ◽  
Cyanobacterial Community ◽  
Moss Species

<p>Nitrogen (N<sub>2</sub>) fixation performed by moss-associated cyanobacteria is one of the main sources of new N in pristine, high latitude ecosystems like boreal forests and arctic tundra. Here, mosses and associated cyanobacteria can contribute more than 50% to total ecosystem N input. However, N<sub>2</sub> fixation in mosses is strongly influenced by abiotic factors, in particular moisture and temperature. Hence, climate change will significantly affect this key ecosystem process in pristine ecosystems. Here, I will present a synthesis of several field and laboratory assessments of moss-associated N<sub>2</sub> fixation in response to climate change by manipulating moisture and temperature in subarctic and arctic tundra.</p><p>Both in a long-term climate warming experiment in the arctic, and along a continental climate gradient, spanning arctic, subarctic and temperate ecosystems, increased temperatures (up to 30 °C) lead to either no effect or decreased N<sub>2</sub> fixation rates in different moss species. Yet, N<sub>2</sub> fixation rates were strongly dependent on moss-moisture, which seems to be a more important driver of N<sub>2</sub> fixation in mosses than temperature.</p><p>In another set of studies, two dominant moss species (Hylocomium splendens, Pleurozium schreberi) were collected from a steep precipitation gradient (400-1200 mm mean annual precipitation, MAP) in the Subarctic close to Abisko, Northern Sweden, and were incubated at different moisture and temperature levels in the laboratory. Nitrogen fixation, cyanobacterial abundance (via qPCR) and cyanobacterial community composition (via sequencing) on the mosses were assessed. Moisture and temperature interacted strongly to control moss-associated N<sub>2</sub> fixation rates, and the highest activity was found at the wet end of the precipitation gradient. Although cyanobacterial abundance was higher in one of the investigated mosses (H. splendens), translating into higher N<sub>2</sub> fixation rates, cyanobacterial community composition did not differ between the two moss species. Nostoc was the most common cyanobacterial genera on both mosses, and hardly any methanotrophic N<sub>2</sub> fixing bacteria were found on the mosses along the precipitation gradient. Increased temperatures lead to increased abundances of certain cyanobacterial genera (Cylindrospermum and Nostoc), while others declined in response to warming. Hence, cyanobacterial communities colonizing mosses will be dominated by a few cyanobacteria species in a warmer climate, and temperature and moisture interact strongly to affect their activity. Thus, these two major climate change factors should be considered in unison when estimating climate change effects on key ecosystem processes such as N<sub>2</sub> fixation. Further, host identity determines cyanobacterial abundance, and thereby, N<sub>2</sub> fixation rates.</p><p> </p><p> </p><p> </p>

Climate Science and the Phlogiston Theory

2007 ◽  
Vol 18 (3-4) ◽  
pp. 441-448
Author(s):  
Arthur Rorsch
Keyword(s):  
Climate Change ◽  
History Of Science ◽  
Climate Changes ◽  
Fossil Fuel ◽  
Climate Science ◽  
Natural Variability ◽  
Phlogiston Theory ◽  
History Of ◽  
Level Of Knowledge

On 2 February 2007 the Intergovernmental Governmental Panel for Climate Change (IPCC) released a “Summary for Policymakers” which is a precis – written by its representatives, not all of whom were scientists – of its longer report, due for release in May. Drafts of the as-yet unpublished main report have been widely circulated and prompted much comment but views which differ from that of the IPCC and the main authors have been largely neglected. In response to the SPM ten scientists presented an alternative report based on the IPCC's draft document and this Independent Summary for Policymakers (ISPM) was released in London on February 5. The ISPM notes the limited level of knowledge of climate sciences and comments on hypotheses neglected by the IPCC SPM, and not surprisingly its conclusions contradict those of the IPCC. The rather alarmist IPCC SPM claims that it is between 90% and 95% probable that the observed climate change since 1950 has mainly been caused by mankind and in particular by the emission of CO2 produced by the burning of fossil fuel. In contrast the ISPM states that the extent to which humans are contributing to climate change is uncertain and will remain uncertain for some time. The ISPM also points out that that the observed climate changes are still within the limits of natural variability and can be explained by natural events, and suggests that some warming might be beneficial. This paper considers this controversy from the perspective of the history of science and shows precendents for questioning science orthodoxy.

scholarly journals From emission scenarios to spatially resolved projections with a chain of computationally efficient emulators: MAGICC (v7.5.1) – MESMER (v0.8.1) coupling

2021 ◽  
Author(s):  
Lea Beusch ◽  
Zebedee Nicholls ◽  
Lukas Gudmundsson ◽  
Mathias Hauser ◽  
Malte Meinshausen ◽  
...  
Keyword(s):  
Climate Change ◽  
Greenhouse Gas Emission ◽  
Regional Scale ◽  
Local Scale ◽  
Natural Variability ◽  
Climate Response ◽  
Computationally Efficient ◽  
Spatially Resolved ◽  
Mitigation And Adaptation ◽  
Uncertainty Space

Abstract. Producing targeted climate information at the local scale, including major sources of climate change projection uncertainty for diverse emissions scenarios, is essential to support climate change mitigation and adaptation efforts. Here, we present the first chain of computationally efficient Earth System Model (ESM) emulators allowing to rapidly translate greenhouse gas emission pathways into spatially resolved annual-mean temperature anomaly field time series, accounting for both forced climate response and natural variability uncertainty at the local scale. By combining the global-mean, emissions-driven emulator MAGICC with the spatially resolved emulator MESMER, ESM-specific as well as constrained probabilistic emulated ensembles can be derived. This emulation chain can hence build on and extend large multi-ESM ensembles such as the ones produced within the 6th phase of the Coupled Model Intercomparison Project (CMIP6). The main extensions are threefold. (i) A more thorough sampling of the forced climate response and the natural variability uncertainty is possible with millions of emulated realizations being readily created. (ii) The same uncertainty space can be sampled for any emission pathway, which is not the case in CMIP6, where some of the most societally relevant strong mitigation scenarios have been run by only a small number of ESMs. (iii) Other lines of evidence to constrain future projections, including observational constraints, can be introduced, which helps to refine projected future ranges beyond the multi-ESM ensemble's estimates. In addition to presenting results from the coupled MAGICC-MESMER emulator chain, we carry out an extensive validation of MESMER, which is trained on and applied to multiple emission pathways for the first time in this study. The newly developed MAGICC-MESMER coupled emulator will allow unprecedented assessments of the implications of manifold emissions pathways at regional scale.

scholarly journals The Phenomenon of Climate Change in Organization and HR-Related Literature: A Conceptual Brief Analysis

2018 ◽  
Vol 10 (1) ◽  
pp. 23-27
Author(s):  
Mohamed Mousa
Keyword(s):  
Climate Change ◽  
Human Activity ◽  
Natural Variability ◽  
Related Literature ◽  
The Past ◽  
Important Phenomenon ◽  
Scientific Disciplines ◽  
Organizational Literature

Abstract Climate change has become one of the main challenges facing humanity. Over the past decade, this phenomenon, which may have been caused by natural variability and/or human activity, has attracted many scholars from different scientific disciplines to warn of its potential consequences. The author of this paper has decided to address the existence of this important phenomenon in organizational literature. However, upon exploring different academic databases, the rarity of research focusing on climate change and its relationship and/or effect on HR or organizational aspects became obvious. Accordingly, the author recommends other HR and organizational scholars devote considerable space to this phenomenon in their field.

scholarly journals Spatiotemporal patterns of tundra fires: late-Quaternary charcoal records from Alaska

2015 ◽  
Vol 12 (3) ◽  
pp. 3177-3209 ◽  
Author(s):  
M. L. Chipman ◽  
V. Hudspith ◽  
P. E. Higuera ◽  
P. A. Duffy ◽  
R. Kelly ◽  
...  
Keyword(s):  
Climate Change ◽  
Late Quaternary ◽  
Rotation Period ◽  
Arctic Tundra ◽  
Ecosystem Processes ◽  
Anthropogenic Climate Change ◽  
The Arctic ◽  
Spatial And Temporal Patterns ◽  
The Past ◽  
Tundra Ecosystem

Abstract. Anthropogenic climate change has altered many ecosystem processes in the Arctic tundra and may have resulted in unprecedented fire activity. Evaluating the significance of recent fires requires knowledge from the paleo-fire record because observational data in the Arctic span only several decades, much shorter than the natural fire rotation in Arctic tundra regions. Here we report results of charcoal analysis on lake sediments from four Alaskan lakes to infer the broad spatial and temporal patterns of tundra fire occurrence over the past 35 000 years. Background charcoal accumulation rates are low in all records (range = 0–0.05 pieces cm-2 year-1), suggesting minimal biomass burning across our study areas. Charcoal peak analysis reveals that the mean fire return interval (FRI; years between consecutive fire events) ranged from 1648 to 6045 years at our sites, and that the most recent fire events occurred from 882 to 7031 years ago, except for the CE 2007 Anaktuvuk River Fire. These mean FRI estimates are longer than the fire rotation periods estimated for the past 63 years in the areas surrounding three of the four study lakes. This result suggests that the frequency of tundra burning was higher over the recent past compared to the late Quaternary in some tundra regions. However, the ranges of FRI estimates from our paleo-fire records overlap with the expected values based on fire-rotation-period estimates from the observational fire data, and thus quantitative differences are not significant. Together with previous tundra-fire reconstructions, these data suggest that the rate of tundra burning was spatially variable and that fires were extremely rare in our study areas throughout the late Quaternary. Given the rarity of tundra burning over multiple millennia in our study areas and the pronounced effects of fire on tundra ecosystem processes such as carbon cycling, dramatic tundra ecosystem changes are expected if anthropogenic climate change leads to more frequent tundra fires.

scholarly journals Emerging climate signals in the Lena River catchment: a non-parametric statistical approach

2020 ◽  
Vol 24 (5) ◽  
pp. 2817-2839
Author(s):  
Eric Pohl ◽  
Christophe Grenier ◽  
Mathieu Vrac ◽  
Masa Kageyama
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Climate Models ◽  
Climate Model ◽  
Natural Variability ◽  
Climate Signal ◽  
Lena River ◽  
River Catchment ◽  
Model Simulations ◽  
Non Parametric

Abstract. Climate change has far-reaching implications in permafrost-underlain landscapes with respect to hydrology, ecosystems, and the population's traditional livelihoods. In the Lena River catchment, eastern Siberia, changing climatic conditions and the associated impacts are already observed or expected. However, as climate change progresses the question remains as to how far we are along this track and when these changes will constitute a significant emergence from natural variability. Here we present an approach to investigate temperature and precipitation time series from observational records, reanalysis, and an ensemble of 65 climate model simulations forced by the RCP8.5 emission scenario. We developed a novel non-parametric statistical method to identify the time of emergence (ToE) of climate change signals, i.e. the time when a climate signal permanently exceeds its natural variability. The method is based on the Hellinger distance metric that measures the similarity of probability density functions (PDFs) roughly corresponding to their geometrical overlap. Natural variability is estimated as a PDF for the earliest period common to all datasets used in the study (1901–1921) and is then compared to PDFs of target periods with moving windows of 21 years at annual and seasonal scales. The method yields dissimilarities or emergence levels ranging from 0 % to 100 % and the direction of change as a continuous time series itself. First, we showcase the method's advantage over the Kolmogorov–Smirnov metric using a synthetic dataset that resembles signals observed in the utilized climate models. Then, we focus on the Lena River catchment, where significant environmental changes are already apparent. On average, the emergence of temperature has a strong onset in the 1970s with a monotonic increase thereafter for validated reanalysis data. At the end of the reanalysis dataset (2004), temperature distributions have emerged by 50 %–60 %. Climate model projections suggest the same evolution on average and 90 % emergence by 2040. For precipitation the analysis is less conclusive because of high uncertainties in existing reanalysis datasets that also impede an evaluation of the climate models. Model projections suggest hardly any emergence by 2000 but a strong emergence thereafter, reaching 60 % by the end of the investigated period (2089). The presented ToE method provides more versatility than traditional parametric approaches and allows for a detailed temporal analysis of climate signal evolutions. An original strategy to select the most realistic model simulations based on the available observational data significantly reduces the uncertainties resulting from the spread in the 65 climate models used. The method comes as a toolbox available at https://github.com/pohleric/toe_tools (last access: 19 May 2020).

scholarly journals Detecting anthropogenic effects in the observational evidence of climate change

2008 ◽  
Vol 87 (3) ◽  
pp. 217-217 ◽  
Author(s):  
H. von Storch
Keyword(s):  
Climate Change ◽  
Air Temperature ◽  
Natural Variability ◽  
Ne Atlantic ◽  
Dynamical Models ◽  
Detection And Attribution ◽  
Attribution Analysis ◽  
Rational Debate ◽  
Recent Trends ◽  
Historical Range

AbstractThe issue of detecting changes beyond the range of natural variability (detection) and of attributing causes to such changes (attribution) are central to any rational debate about anthropogenic climate change. This concept, introduced by Klaus Hasselmann in the late 1970s, is usually not understood by either so-called sceptics or by activist scientists.Often rigorous detection and attribution analysis is replaced by mere declarations and by naïve applications of methods to determine if certain trends are ‘significant’ or not.In this talk, the concepts are introduced; the invoked assumptions and the roles of dynamical models and of time-scales are explained. The concept is illustrated with a few examples related to global and regional air temperature and to NE Atlantic storminess.For global and regional air temperature, the recent variations are found to be beyond the range of natural variability (detection) and the changes are best explained by a dominant contribution by elevated greenhouse gas concentrations. For NE Atlantic storminess recent trends are found to be intermittent and within the historical range of variations. The finding of significant GHG contributions to temperature change and the lack of such for changes in storminess are not contradictions.

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