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What follows below is a list of 48 scientific papers published this year alone showing that CO2 climate science is not what the press and activist scientists like to have us believe it is.

Image: National Academy of Sciences logo

Recently I posted here on about 250 papers published in 2015. That post was shared or liked a few thousand times.

Well, the number of skeptic papers seems to be accelerating as already this year there have been almost 50, and it’s only February!

The following lists 48 scientific papers listed show that CO2 climate science is exaggerated and that natural factors are indeed dominant climate forces that will not be tamed by man emitting a trace gas.

These newest findings of course are no surprise to skeptics.

The list below includes the abstracts, where the special points have been emphasized. Two of the papers have been discussed already at NTZ here and here. The papers have been sorted according to categories.

Again do feel free to bring this newest list to the attention of your lawmakers, and ask them if there might be much better things to do with the billions of dollars spent on junk climate measures. It’s becoming crystal clear as to who the real deniers really are.

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Solar Influence on Climate

http://www.sciencedirect.com/science/article/pii/S1364682615300985

The various techniques have been used to confer the existence of significant relations between the number of Sunspots and different terrestrial climate parameters such as rainfall, temperature, dewdrops, aerosol and ENSO etc. Improved understanding and modelling of Sunspots variations can explore the information about the related variables. This study uses a Markov chain method to find the relations between monthly Sunspots and ENSO data of two epochs (1996–2009 and 1950–2014). Corresponding transition matrices of both data sets appear similar and it is qualitatively evaluated by high values of 2-dimensional correlation found between transition matrices of ENSO and Sunspots. The associated transition diagrams show that each state communicates with the others. Presence of stronger self-communication (between same states) confirms periodic behaviour among the states. Moreover, closeness found in the expected number of visits from one state to the other show the existence of a possible relation between Sunspots and ENSO data. Moreover, perfect validation of dependency and stationary tests endorses the applicability of the Markov chain analyses on Sunspots and ENSO data. This shows that a significant relation between Sunspots and ENSO data exists. Improved understanding and modelling of Sunspots variations can help to explore the information about the related variables. This study can be useful to explore the influence of ENSO related local climatic variability.

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http://www.sciencedirect.com/science/article/pii/S0277379115301682

Here, we use diatom assemblages from a marine sediment core collected from the West Greenland shelf to reconstruct changes in sea-ice cover over the last millennium. The proxy-based reconstruction demonstrates a generally strong link between changes in sea-ice cover and solar variability during the last millennium. Weaker (or stronger) solar forcing may result in the increase (or decrease) in sea-ice cover west of Greenland.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4709040/

The comparison between MDVM reconstructed temperature and the variation of external forcing (solar activity and volcanic activity) is shown in Fig. 5. The smoothed MDVM reconstruction exhibited a general agreement with the variation of the reconstructed total solar irradiance (TSI), and the correlation between the two series during the common period 849–2000 AD was significant (r = 0.498, edf = 34, p<0.01). Specially, the records shared high correlation coefficients in the epochs of the solar maximum (i.e. during the Medieval and Modern age), but poor correlation around 1500–1700 AD when the Spörer Minimum and Maunder Minimum occurred. It was similar to some other dendrochronological researches concerning the relation with solar activity. The relatively cold conditions between the two warm peaks around AD 1000 and 1100 seemed to be related to the Oort Minimum.

Therefore, the temperature reconstructions based on the MDVM method agreed well in general with the characteristic variations of the solar and volcanic forcings. It is quite plausible that the long-term climate variations in the past millennium have been largely linked to the periodical solar activity, and people usually look at the Maunder Minimum to explain the LIA. However, some researchers argued that solar forcing probably had a minor effect on the climate change over the past 1000 years, and volcanic eruptions seemed to be an important driver for the climate particularly during the LIA. It was also reported that the abrupt onset of the LIA was likely triggered by a succession of strong volcanic eruptions and sustained by sea-ice/ocean feedbacks. According to mainstream opinions, the LIA type events were probably attributed to a combination of solar minima and volcanic eruptions.

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http://link.springer.com/article/10.1007/s40333-015-0138-5

Tree-ring-based reconstruction of temperature variability (1445–2011) for the upper reaches of the Heihe River Basin, Northwest China

Spectral analyses suggested that the reconstructed annual mean temperature variation may be related to large-scale atmospheric–oceanic variability such as the solar activity, Pacific Decadal Oscillation (PDO) and El Niño–Southern Oscillation (ENSO).

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http://www.sciencedirect.com/science/article/pii/S1364682616300347

The impact of solar activity on tropical Pacific convection during the boreal summer (June-July-August, JJA) has been examined using reanalysis data, revealing a significant lagged (1–2 years) correlation between outgoing long-wave radiation (OLR) over the tropical western Pacific and the F10.7 index. The OLR anomaly over the tropical western Pacific and the maritime continent shows a dipole pattern during the 1–2 years following high solar (HS) years. Furthermore, the first mode of the empirical orthogonal function (EOF) analysis on the OLR with the El Niño/Southern Oscillation (ENSO) signal removed is similar to the distribution of correlation coefficients between the JJA mean F10.7 index and the OLR with ENSO signal removed. The correlation and composite analyses of the OLR, velocity potential and vertical velocity reveals that this convection dipole pattern shows an eastward shift of the central position of deep convection, as related to the influence of solar activity over the tropical western Pacific. Further analyses show that the evolutionary process of the solar signal in the ocean-atmosphere system over the tropical western Pacific is consistent with the analyses of OLR, velocity potential, and vertical velocity. By modulating vertical air temperature, the solar signal in the tropical sea surface temperature (SST) may contribute to the triggering of a lagged convection dipole pattern.

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http://hol.sagepub.com/content/early/2015/12/23/0959683615618265.abstract

The reconstructions show a large glacier readvance corresponding with the 8.2-ka cold event and a sequence of eight distinct glacier advances and retreats during the Neoglacial time period bracket between 4300 ± 40 cal. yr BP and AD 1900. … [W]e suggest that deviations in ELA fluctuations between Scandinavian maritime and continental glaciers around 7150, 6560, 6000, 5150, 3200 and 2200 cal. yr BP reflect the different response of continental and maritime glaciers to drops in total solar irradiance (TSI).

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http://link.springer.com/article/10.1007/s10933-015-9861-3

[W]e reconstructed the history of typhoon and storm-rain activity only for the interval AD 1400–1900. The record indicates that typhoon frequency throughout the Korean Peninsula varied in response to the state of the El Niño/Southern Oscillation. Typhoon variability was likely modulated further by the state of the East Asia summer monsoon (EASM) pattern, associated with variation in the magnitude of solar irradiance. During periods of minimum solar activity, such as the early Maunder Minimum (AD 1650–1675), typhoons struck the east China coast and Korean Peninsula more frequently because of a strengthened EASM.

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http://www.sciencedirect.com/science/article/pii/S1364682616300360

A significant correlation between the solar wind speed (SWS) and sea surface temperature (SST) in the region of the North Atlantic Ocean has been found for the Northern Hemisphere winter from 1963 to 2010, based on 3-month seasonal averages. The correlation is dependent on Bz (the interplanetary magnetic field component parallel to the Earth’s magnetic dipole) as well as the SWS, and somewhat stronger in the stratospheric quasi-biennial oscillation (QBO) west phase than in the east phase. The correlations with the SWS are stronger than those with the F10.7 parameter representing solar UV inputs to the stratosphere. SST responds to changes in tropospheric dynamics via wind stress, and to changes in cloud cover affecting the radiative balance. Suggested mechanisms for the solar influence on SST include changes in atmospheric ionization and cloud microphysics affecting cloud cover, storm invigoration, and tropospheric dynamics. Such changes modify upward wave propagation to the stratosphere, affecting the dynamics of the polar vortex. Also, direct solar inputs, including energetic particles and solar UV, produce stratospheric dynamical changes. Downward propagation of stratospheric dynamical changes eventually further perturbs tropospheric dynamics and SST.

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https://www.researchgate.net/profile/Miguel_Angel_Morales_Maqueda2/publication/265355775_Physics_and_climatology_of_sea_ice/links/54900f170cf214269f264b93.pdf

Three factors affect substantially the radiation balance in polar regions: surface albedo, surface air temperature, and cloudiness. The surface albedo controls the shortwave energy budget; surface air temperature determines the incoming longwave radiation; cloudiness alters both the solar and the infrared radiative components.

Low Solar Activity Leads to Cooling…

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http://www.clim-past-discuss.net/cp-2016-7/cp-2016-7.pdf

Climate reconstructions from a multitude of natural and human archives indicate that, during winter, the period of the early Spörer Minimum (1431–1440 CE) was the coldest decade in Central Europe in the 15th century. The particularly cold winters and normal but wet summers resulted in a strong seasonal cycle that challenged food production and led to increasing food prices, a subsistence crisis, and a famine in parts of Europe. As a consequence, authorities implemented adaptation measures, such as the installation of grain storage capacities, in order to be prepared for future events. The 15th century is characterised by a grand solar minimum and enhanced volcanic activity, which both imply a reduction of seasonality. Climate model simulations show that periods with cold winters and strong seasonality are associated with internal climate variability rather than external forcing. Accordingly, it is hypothesised that the reconstructed extreme climatic conditions during this decade occurred by chance and in relation to the partly chaotic, internal variability within the climate system.

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http://link.springer.com/article/10.1007/s12303-015-0058-6

We present a multi-proxy record (pollen, microscopic charcoal, carbon-isotopic composition [δ13C], organic content, and particle size) of the late-Holocene climate change and human impact from central-eastern South Korea. The Medieval Climate Anomaly (MCA) and Little Ice Age (LIA), the most recent major climate events, have not been accurately investigated by paleolimnological studies in Korea, mainly due to a lack of undisturbed sediments and indifference to the past climate change. Our pollen records show late- Holocene centennial climate variations characterized by the successive solar minimums of the Oort, Wolf, Spörer, Maunder, and Dalton. We find paleoenvironmental evidence for shifting cultivation associated with serious droughts and consequent famines during the early 19th-century Dalton minimum. Our interpretation of human activities is well supported by Korean historical documents describing socioeconomic suffering induced by LIA climate deteriorations.

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http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2652.html

Climatic changes during the first half of the Common Era have been suggested to play a role in societal reorganizations in Europe and Asia. In particular, the sixth century coincides with rising and falling civilizations, pandemics, human migration and political turmoil. Our understanding of the magnitude and spatial extent as well as the possible causes and concurrences of climate change during this period is, however, still limited. Here we use tree-ring chronologies from the Russian Altai and European Alps to reconstruct summer temperatures over the past two millennia. We find an unprecedented, long-lasting and spatially synchronized cooling following a cluster of large volcanic eruptions in 536, 540 and 547 AD, which was probably sustained by ocean and sea-ice feedbacks, as well as a solar minimum. We thus identify the interval from 536 to about 660 AD as the Late Antique Little Ice Age. Spanning most of the Northern Hemisphere, we suggest that this cold phase be considered as an additional environmental factor contributing to the establishment of the Justinian plague, transformation of the eastern Roman Empire and collapse of the Sasanian Empire, movements out of the Asian steppe and Arabian Peninsula, spread of Slavic-speaking peoples and political upheavals in China.

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Natural Ocean Oscillation

http://onlinelibrary.wiley.com/doi/10.1002/2016GL067679/full

The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of climatic impacts. While the tropical arm of AMO is responsible for many of these impacts, it is either too weak or completely absent in many climate model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is strong enough to generate the tropical arm of AMO, with the low cloud feedback more dominant. The feedbacks can be understood in a consistent dynamical framework: weakened tropical trade wind speed in response to a warm middle latitude SST anomaly reduces dust loading and low cloud fraction over the tropical Atlantic, which warms the tropical North Atlantic SST. Together they contribute to appearance of the tropical arm of AMO. Most current climate models miss both the critical wind speed response and two positive feedbacks though realistic simulations of them may be essential for many climatic studies related to the AMO.

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http://onlinelibrary.wiley.com/doi/10.1002/wea.2558/full

Introduction: The surface climate of the UK and northern Europe is up to 9 degC warmer than it would be if the North Atlantic Ocean did not transport a large quantity of heat northwards to our shores. This unusual warming has been known since sea temperature records were established in the late nineteenth century and was probably well known to the early seafarers in the last two millennia.

Summary: This article has indicated that the North Atlantic Ocean is showing changes in its circulation as represented by the MOC at 26°N in the last 10 years. The changes in the MOC are associated with heat transport which has a direct effect on the upper ocean heat storage northwards of the RAPID array. The event in 2009 caused a cooling of the subtropical ocean between 20 and 40°N but did not appear to influence the region poleward of 50°N. The role of the atmosphere in the changes in the MOC in this region, in particular on interannual and decadal timescales, is still not well understood.

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http://www.sciencedirect.com/science/article/pii/S0012821X15007669

The North Atlantic Oscillation (NAO) is the leading mode of atmospheric circulation variability in the North Atlantic region. Associated shifts of storm tracks, precipitation and temperature patterns affect energy supply and demand, fisheries and agricultural, as well as marine and terrestrial ecological dynamics. Long-term NAO records are crucial to better understand its response to climate forcing factors, and assess predictability and shifts associated with ongoing climate change. A recent study of instrumental time series revealed NAO as main factor for a strong relation between winter temperature, precipitation and river discharge in central Norway over the past 50 years. … Conditioned on a stationary relation between our climate proxy and the NAO we establish a first high resolution NAO proxy record from marine sediments covering the past 2800 years. The [NAO proxy record] shows distinct co-variability with climate changes over Greenland, solar activity and Northern Hemisphere glacier dynamics as well as climatically associated paleo-demographic trends. The here presented climate record shows that fjord sediments provide crucial information for an improved understanding of the linkages between atmospheric circulation, solar and oceanic forcing factors.

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http://www.mdpi.com/2225-1154/4/1/5/htm

Conclusions: The temperatures observed from the different locations within Nigeria between 1980 and 2010 (1983–2010 for Abuja) are compared with the SST from the Niño 3 and Niño 4 regions of the Tropical Pacific while a further comparison of the temperature with the rainfall in Nigeria is also done. This is necessary so as to establish the connections between an ENSO event and the climate patterns in Nigeria. The outcome shows good link between the ENSO events and the Nigerian climate with the strongest agreement coming from the Niño 3 region of the Tropical Pacific. The finding indicates that the primary driver of climate like the south-westerlies that brings monsoon into the country from South Atlantic Ocean, the north-easterlies that lead to Tropical dry climate in the North and the ITCZ, which is sandwiched between the air masses, could be affected by changes in ENSO events. According to the results, the major link between an ENSO event and changes in the temperature and rainfall in Nigeria is associated with shifts in the ITCZ position. An El Niño (La Niña) induced southward (northward) shift in the ITCZ mean position is accompanying by reduction (increase) in the intensity of the mean rainfall in the country while the corresponding mean temperature after an El Niño (La Niña) event will rise (reduce). This is similar to other studies where El Niño induced drought have been reported in Nigeria

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http://link.springer.com/article/10.1007/s11069-015-2039-5#/page-1

Most of flood periods coincided with the warm phase of the Atlantic Multidecadal Oscillation (AMO). The flood period of 1940–1944 was as long as the most recent one (2007–2011). Wavelet analysis found flood periodicities of 2.5, 52 and 83 years, but only the last one was statistical significant and their occurrence was in phase with the AMO. Logistic regression showed that AMO index was the most correlated index with flood events. In fact, the odds ratio showed that floods were 1.90 times more likely to occur when AMO index was positive. This regression model predicted correctly 64.70 % of flood occurrences during twentieth century using its flood information only as validation data.

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http://link.springer.com/article/10.1007/s00382-016-2973-2

The climate variability on Earth is strongly influenced by the changes in the Sea Surface Temperature (SST) anomalies in the tropical oceans. More specifically, the inter-annual climate variability in the tropics as well as extra-tropical areas has large impact due to the anomalous SSTs in the tropical Pacific coupled with the El Niño Southern Oscillation (ENSO) through atmospheric teleconnections. … It is observed that during El Niño years the peninsular region receives more rainfall through enhanced moisture transport associated with anomalous westerly winds from adjoining Seas. The Rossby wave energy propagation in the atmosphere underlies important teleconnections involving ENSO. It is also noticed that there exist a distinct change in the phase of the Rossby wave pattern during El Niño and La Niña years which further causes the shift in the position of the jet stream over the Middle East.

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http://onlinelibrary.wiley.com/doi/10.1002/joc.4660/abstract

Furthermore, since the end of the 19th century, we find an increasing variance in multidecadal hydroclimatic winter and spring, and this coincides with an increase in the multidecadal North Atlantic Oscillation (NAO) variability, suggesting a significant influence of large-scale atmospheric circulation patterns. However, multidecadal NAO variability has decreased in summer. Using Empirical Orthogonal Function analysis, we detect multidecadal North Atlantic sea-level pressure anomalies, which are significantly linked to the NAO during the Modern period. In particular, a south-eastward (south-westward) shift of the Icelandic Low (Azores High) drives substantial multidecadal changes in spring. Wetter springs are likely to be driven by potential changes in moisture advection from the Atlantic, in response to northward shifts of North Atlantic storm tracks over European regions, linked to periods of positive NAO. Similar, but smaller, changes in rainfall are observed in winter.

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http://www.sciencedirect.com/science/article/pii/S0277379116300129

In 2012 the most severe United States drought since the 1930’s occurred, highlighting the need for a better understanding of the climate factors driving droughts. Spatial-temporal analysis of United States precipitation data from 1900 to 1999 indicates that the Atlantic Multidecadal Oscillation (AMO) primarily modulates drought frequency. … Using this transfer function, a 954-year tree-ring drought record was extended to ca. 3000 BP. Changes in the extended drought record correspond with timing of the Roman Climate Optimum, Medieval Warm Period, Little Ice Age, and changes in the AMO as recorded in a proxy record derived from North Atlantic ice-rafted debris. These results indicate that lacustrine-derived XRF element data can be used as a quantitative tool to reconstruct past drought records, and suggest that AMO modulated drought in southern Texas for the last 3000 years. Additional studies using XRF-derived element data as a drought proxy are needed to determine the utility of this proxy in non-playa lacustrine systems.

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http://link.springer.com/article/10.1007%2Fs00704-016-1752-7

Multiscale evolution of surface air temperature in the arid region of Northwest China and its linkages to ocean oscillations

The global climate has experienced unprecedented warming in the past century. The multiscale evolution of the warming is studied to better understand the spatial and temporal variation patterns of temperature. In this study, based on the yearly surface air temperature from the gridded CRU TS 3.22 dataset and the ensemble empirical mode decomposition method (EEMD), we investigated the multiscale evolution of temperature variability in the arid region of Northwest China (ARNC) from 1901 to 2013. Furthermore, the possible influences on the ARNC temperature change from the Atlantic Multidecadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), and dipole mode index (DMI) were also discussed. The results indicated that in the past century, the overall temperature in the ARNC has showed a significant non-linear upward trend, and its changes have clearly exhibited an interannual scale (quasi-2–3 and quasi-6–7-year) and an interdecadal scale (quasi-14, quasi-24, and quasi-70-year). Compared with the reconstructed interannual variation, the reconstructed interdecadal variability plays a decisive role in the ARNC warming and reveals the climatic pattern transformation from the cold period to the warm period before and after 1987. Additionally, there were also regional differences in the spatial patterns of change trend in the ARNC temperature at a given time. We also found that the AMO and PDO had significant impacts on the ARNC temperature fluctuation at an interdecadal scale, whereas the DMI had a more important role in warming at the annual scale, which suggests that the importance of oceans cannot be ignored when considering climate change. Our findings deepen the understanding of the temperature changes all over the ARNC in the context of global warming.

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http://onlinelibrary.wiley.com/doi/10.1002/qj.2759/abstract

Identifying predictability sources of heat wave variations is a scientific challenge and of practical importance. This study investigates the summertime heat wave frequency (HWF) over Eurasia for 1950–2014. … Further analysis suggests that mega-ENSO variations can incite a Gill-type response spreading to Eurasia, while the AMO changes cause eastward-propagating Rossby wave trains toward Eurasia. These two teleconnection patterns together contribute to the large-scale circulation anomalies of the ID mode, and those related to the IA mode arise from the teleconnection pattern excited by mega-ENSO. A strong mega-ENSO triggers subsidence with high pressure anomalies, warms the surface and increases the HWF significantly over northeastern Asia particularly. Likewise, the warm AMO-induced circulation anomalies engender surface radiative heating and HWF growth in most of Eurasian continent except some localized Siberian and Asian regions. The situation is opposite for a weak mega-ENSO and AMO. Those models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) which realistically capture the features of the ID mode can reproduce the AMO-like sea surface temperature anomalies (SSTAs), while signals resembling mega-ENSO are found in those with favorable capability of simulating the IA mode. On the contrary, these relevant SSTAs linked to the respective modes vanish in the models with little skills. Thus, mega-ENSO and the AMO might provide two critical predictability sources for heat waves over Eurasia.

Natural Variability

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0226.1

Forced atmospheric teleconnections during 1979-2014 are examined using a 50-member ensemble of atmospheric general circulation model (AGCM) simulations subjected to observed variations in sea surface temperatures (SST), sea ice and carbon dioxide. … A trend in the leading forced mode is related to ENSO-like decadal variability and dominates the overall observed 500 hPa height trend since 1979. These model results indicate that the trend in the first mode is due to internal variability rather than external radiative forcings.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0441.1

Time series of US daily heavy precipitation (95th percentile) are analyzed to determine factors responsible for regionality and seasonality in their 1979-2013 trends. …. Analysis of model ensemble spread reveals that appreciable 35-yr trends in heavy daily precipitation can occur in the absence of forcing, thereby limiting detection of the weak anthropogenic influence at regional scales.

Analysis of the seasonality in heavy daily precipitation trends supports physical arguments that their changes during 1979-2013 have been intimately linked to internal decadal ocean variability, and less to human-induced climate change. Most of the southern US decrease has occurred during the cold season that has been dynamically driven by an atmospheric circulation reminiscent of teleconnections linked to cold tropical east Pacific SSTs. Most of the northeast US increase has been a warm season phenomenon; the immediate cause for which remains unresolved.

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http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0301.1

On the interannual time scale, ENSO and SAM are important, but a large fraction of sea ice variance can also be explained by Rossby wave–like structures in the Drake Passage region. After regressing out the sea ice extent variability associated with ENSO, the observed positive sea ice trends in Ross Sea and Indian Ocean during the satellite era become statistically insignificant. Regressing out SAM makes the sea ice trend in the Indian Ocean insignificant. Thus, the positive trends in sea ice in the Ross Sea and the Indian Ocean sectors may be explained by the variability and decadal trends of known interannual climate modes.

Climate of the Past

http://www.sciencedirect.com/science/article/pii/S0277379115301876

Glaciers and small ice caps respond rapidly to climate perturbations (mainly winter precipitation, and summer temperature), and the mass-balance of glaciers located in western Norway is governed mainly by winter precipitation (Pw). … Complete deglaciation of the Ålfotbreen [glacier] occurred ∼9700 cal yr BP, and the ice cap was subsequently absent or very small until a short-lived glacier event is seen in the lake sediments ∼8200 cal yr BP. The ice cap was most likely completely melted until a new glacier event occurred around ∼5300 cal yr BP, coeval with the onset of the Neoglacial at several other glaciers in southwestern Norway. Ålfotbreen was thereafter absent (or very small) until the onset of the Neoglacial period ∼1400 cal yr BP. The ‘Little Ice Age’ (LIA) ∼650–50 cal yr BP was the largest glacier advance of Ålfotbreen since deglaciation, with a maximum extent at ∼400–200 cal yr BP, when the ELA [equilibrium-line-altitude] was lowered approximately 200 m relative to today.

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http://hol.sagepub.com/content/26/1/154.abstract?rss=1

Here, we present evidence for glacial retreat corresponding to the MWP [Medieval Warm Period] and a subsequent LIA [Little Ice Age] advance at Rothera Point (67°34′S; 68°07′W) in Marguerite Bay, western Antarctic Peninsula. Deglaciation started at ca. 961–800 cal. yr BP or before, reaching a position similar to or even more withdrawn than the current state, with the subsequent period of glacial advance commencing between 671 and 558 cal. yr BP and continuing at least until 490–317 cal. yr BP. Based on new radiocarbon dates, during the MWP, the rate of glacier retreat was 1.6 m yr−1, which is comparable with recently observed rates (~0.6 m yr−1 between 1993 and 2011 and 1.4 m yr−1 between 2005 and 2011). Moreover, despite the recent air warming rate being higher, the glacial retreat rate during the MWP was similar to the present, suggesting that increased snow accumulation in recent decades may have counterbalanced the higher warming rate.

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http://link.springer.com/chapter/10.1007/978-3-319-26701-2_6

European Middle Ages were an extended period of fluctuating but mostly above-average warm temperatures that by the tenth century had melted the ice sheet of the Arctic Ocean and brought about Viking marine exploration of, and temporary settlement on the eastern shores of North America. Medieval warm climate was punctuated by two short, but extremely cold events. The first was the cold event of 535–6, possibly due to a volcanic catastrophe in the tropics that yielded extensive atmospheric dust veil, followed by a major crop failure through Europe, North Africa and the Middle East, and a subsequent terrifying pandemic of the years 541–2, the Plague of Justinian. The second cold event coincided with a prolonged series of major volcanic eruptions on the Southern Hemisphere during 1315–1322. Extensive crop failure during the years 1315–1317 had led, at the same time, to the Great Famine throughout much of Europe.

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http://hol.sagepub.com/content/early/2016/01/12/0959683615622551.abstract

Here we present the first high-resolution late-Holocene glacier record from the Lofoten archipelago in northern Norway. … AMS radiocarbon dating reveals that the lake sediment record covers the last 1200 years, thereby including both the ‘Little Ice Age’ (LIA) and the ‘Medieval Climate Anomaly’ (MCA). …We found that both MCA and LIA were periods of substantial glacier variations with respect to the present, with a maximum lowering of the ELA of ~75 and ~85 m, respectively.

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http://www.sciencedirect.com/science/article/pii/S0277379115301815

Centennial to millennial scale changes in the wider North Atlantic region were accompanied by variations in the West Greenland Current (WGC). During periods of relatively warm WGC, increased surface air temperature over western Greenland led to ice sheet retreat and significant meltwater flux. In contrast, during periods of cold WGC, atmospheric cooling resulted in glacier advances.

We also identify potential linkages between the palaeoceanography of the Disko Bugt region and key changes in the history of human occupation. Cooler oceanographic conditions at 3.5 ka BP support the view that the Saqqaq culture left Disko Bugt due to deteriorating climatic conditions. The cause of the disappearance of the Dorset culture is unclear, but the new data presented here indicate that it may be linked to a significant increase in meltwater flux, which caused cold and unstable coastal conditions at ca. 2 ka BP. The subsequent settlement of the Norse occurred at the same time as climatic amelioration during the Medieval Climate Anomaly and their disappearance may be related to harsher conditions at the beginning of the Little Ice Age.

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http://epic.awi.de/39643/1/cp-12-171-2016.pdf

Compared to single records, this stack represents the mean δ18O signal for northern Greenland that is interpreted as proxy for temperature. Our northern Greenland δ18O stack indicates distinctly enriched [warm] δ18O values during medieval times, about AD 1420 ± 20 and from AD 1870 onwards. The period between AD 1420 and AD 1850 has depleted [cold] δ18O values compared to the average for the entire millennium and represents the Little Ice Age. The δ18O values of the 20th century are comparable to the medieval period but are lower than that about AD 1420. …. The solar activity and internal Arctic climate dynamics are likely the main factors influencing the temperature in northern Greenland. In contrast, we could not find a general cooling effect of volcanic eruptions in our data.

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https://www.researchgate.net/profile/David_Etienne/publication/283719048_Climate_and_human_land-use_as_a_driver_of_Lake_Narlay_Eastern_France_Jura_Mountains_evolution_over_the_last_1200_years_implication_for_methane_cycle/links/564499cc08aef646e6cbb40c.pdf

The climate evolution over the last 1400 years was marked by alternating warm and cold phases. Two main climate periods can be highlighted: the Medieval Warm Period (MWP) and the Little Ice Age (LIA). The MWP is characterized by relatively high temperatures associated with low variability (0.34 C ± 0.37). This period occurred between ca. AD 750 and ca. AD 1200. The LIA constitutes a cold period (-0.11 C ± 0.49) from ca. AD 1200 to ca. AD 1900. The end of the LIA seems late using this study, but it is still agree with several references (Millet et al. 2009; Magny et al. 2011; Luoto 2012). In the climate reconstruction provided by Guiot et al. 2010), two particular phases can be identified in this zone. The first (from ca. AD 1200 to ca. AD 1600) is clearly colder than the second. An abrupt warming appears to occur at AD 1600 during the LIA cold period. Before AD 750, the climate appears to correspond to a cold period, whereas after AD 1900, the climate corresponds to a warming period (0.04 C ± 0.49).

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https://www.sciencedaily.com/releases/2016/02/160219134816.htm

http://www.nature.com/articles/srep20535

Press release (sciencedaily): “Extreme climate changes in the past Ice core records show that Greenland went through 25 extreme and abrupt climate changes during the last ice age some 20,000 to 70,000 years ago. In less than 50 years the air temperatures over Greenland could increase by 10 to 15 °C. However the warm periods were short; within a few centuries the frigid temperatures of the ice age returned. That kind of climate change would have been catastrophic for us today. Ice core records from Antarctica also show climate changes in the same period, but they are more gradual, with less severe temperature swings.”

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http://www.pnas.org/content/early/2016/02/09/1516908113.abstract

The stability of modern ice shelves is threatened by atmospheric and oceanic warming. The geologic record of formerly glaciated continental shelves provides a window into the past of how ice shelves responded to a warming climate. …. The timing of ice-shelf breakup is constrained by compound specific radiocarbon ages, the first application of this technique systematically applied to Antarctic marine sediments. Breakup initiated around 5 ka [5,000 years ago], with the ice shelf reaching its current configuration ∼1.5 ka. In the eastern Ross Sea, the ice shelf retreated up to 100 km in about a thousand years. Three-dimensional thermodynamic ice-shelf/ocean modeling results and comparison with ice-core records indicate that ice-shelf breakup resulted from combined atmospheric warming and warm ocean currents impinging onto the continental shelf.

Climate Model Uncertainties and the Pause

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0191.1

The authors demonstrate that model estimates of climate sensitivity can be strongly affected by the manner through which cumulus cloud condensate is converted into precipitation in a model’s convection parameterization, processes that are only crudely accounted for in GCMs. In particular, two commonly used methods for converting cumulus condensate into precipitation can lead to drastically different climate sensitivity, as estimated here with an atmosphere–land model by increasing sea surface temperatures uniformly and examining the response in the top-of-atmosphere energy balance. The effect can be quantified through a bulk convective detrainment efficiency, which measures the ability of cumulus convection to generate condensate per unit precipitation. The model differences, dominated by shortwave feedbacks, come from broad regimes ranging from large-scale ascent to subsidence regions. Given current uncertainties in representing convective precipitation microphysics and the current inability to find a clear observational constraint that favors one version of the authors’ model over the others, the implications of this ability to engineer climate sensitivity need to be considered when estimating the uncertainty in climate projections.

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http://link.springer.com/article/10.1007/s00382-016-3018-6

Global mean surface temperature (GMST) rising has slowed down since late 1990s, which is referred to as the global warming hiatus. There was another global warming hiatus event during 1940s–1960s. The roles of the external forcing and the natural variability in both global warming hiatuses are explored, using EOF analysis. The first two leading EOF modes of the 5-year running mean global sea surface temperature (SST) reflect the global warming scenario (EOF1) and the interdecadal Pacific oscillation (IPO)-like natural variability (EOF2), respectively. In observation, PC2 was in its positive phase (eastern Pacific cooling) during 1940s–1960s, which contributed to the previous warming hiatus. In addition, GMST trends are found to be negative during late 1950s and 1960s in most of the CMIP5 historical runs, which implies that the external forcing also contributed to the pause in the GMST rising. It is further demonstrated that it is the natural radiative forcing (volcanic forcing) that caused the drop-down of GMST in 1960s. The current global warming hiatus has been attributed to the eastern Pacific cooling/enhanced Pacific trade winds. It is shown that the PC2 switched to its positive phase in late 1990s, and hence the IPO-like natural variability made a contribution to the slowdown of GMST rising in the past decade. It is also found that the EOF1 mode (global warming mode) of the observed SST features a smaller warming in tropical Pacific compared to the Indian Ocean and the tropical Atlantic. Such inter-basin warming contrast, which is attributed to the “ocean thermostat” mechanism, has been suggested to contribute to the intensification of Pacific trade winds since late 1990s as well. Global warming hiatuses are also found in the future projections from CMIP5 models, and the spatial pattern of the SST trends during the warming-hiatus periods exhibits an IPO-like pattern, which resembles the observed SST trends since late 1990s.

Cloud/Aerosol Climate Forcing

http://www.nature.com/ncomms/2016/160112/ncomms10266/pdf/ncomms10266.pdf

The Greenland ice sheet has become one of the main contributors to global sea level rise, predominantly through increased meltwater runoff. The main drivers of Greenland ice sheet runoff, however, remain poorly understood. Here we show that clouds enhance meltwater runoff by about one-third relative to clear skies, using a unique combination of active satellite observations, climate model data and snow model simulations. This impact results from a cloud radiative effect of 29.5 (±5.2)Wm 2. Contrary to conventional wisdom, however, the Greenland ice sheet responds to this energy through a new pathway by which clouds reduce meltwater refreezing as opposed to increasing surface melt directly, thereby accelerating bare-ice exposure and enhancing meltwater runoff. The high sensitivity of the Greenland ice sheet to both ice-only and liquid-bearing clouds highlights the need for accurate cloud representations in climate models, to better predict future contributions of the Greenland ice sheet to global sea level rise.

Clouds are known to play a pivotal role in regulating the local SEB [Surface Energy Balance], with competing warming and cooling effects on the surface. … The satellite-based cloud observations allow to estimate the cloud impact on the SEB [Surface Energy Balance]. … The annual mean CRE [Cloud Radiative Effect] of 29.5 (±5.2) W m 2 provides enough energy to melt 90 Gt of ice in the GrIS [Greenland Ice Sheet] ablation area during July and August. … The snow model simulations, which capture the evolution of the GrIS SMB [Surface Mass Balance] from 2007 to 2010, indicate that clouds warm the GrIS [Greenland Ice Sheet] surface by 1.2 (±0.1) C on average over the entire period [2007-2010]. … These results further indicate that not only liquid-bearing clouds but also clouds composed exclusively of ice significantly increase radiative fluxes into the surface and decrease GrIS SMB [Greenland Ice Sheet Surface Mass Balance]

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http://link.springer.com/article/10.1007/s10584-015-1525-9

Future changes in aerosol concentrations will influence the climate system over the coming decades. In this study we evaluate the equilibrium climate response to aerosol reductions in different parts of the world in 2050, using the global climate model EC-Earth. .. Reductions in aerosol concentrations lead to an increase in downward surface solar radiation under all-sky conditions in various parts of the world, especially in Asia where the local brightening may reach about 10 Wm−2. The associated increase in surface temperature may be as high as 0.5 °C. This signal is dominated by the reduced cooling effect of sulphate which in some areas is partially compensated by the decreased warming effect of black carbon. According to our simulations, the mitigation of BC may lead to decreases in mean summer surface temperature of up to 1 °C in central parts of North America and up to 0.3 °C in northern India. Aerosol reductions could significantly affect the climate at high latitudes especially in the winter, where temperature increases of up to 1 °C are simulated. In the Northern Hemisphere, this strong surface temperature response might be related to changes in circulation patterns and precipitation at low latitudes, which can give rise to a wave train and induce changes in weather patterns at high latitudes. Our model does not include a parameterization of aerosol indirect effects so that responses could be stronger in reality. We conclude that different, but plausible, air pollution control policies can have substantial local climate effects and induce remote responses through dynamic teleconnections

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http://onlinelibrary.wiley.com/doi/10.1002/joc.4603/full

A climate study of the incidence of downward surface global solar radiation (SSRD) in the Iberian Peninsula (IP) based primarily on ERA-40 reanalysis [atmospheric radiance data] is presented. NCEP/NCAR reanalysis and ground-based records from several Portuguese and Spanish stations have been also considered. … [G]round-based measurements in Portuguese stations during the period 1964–1989 show a tendency to decrease until the mid-1970s followed by an increase up to the end of the study period, in line with the dimming/brightening phenomenon reported in the literature. … [T]he ERA-40 reanalysis shows a noticeable decrease until the early 1970s followed by a slight increase up to the end of the 1990s, suggesting a dimming/brightening transition around the early 1970s, earlier in the south and centre and later in the north of the IP. …. The results show that part of the decadal variability of the global radiation in the IP is related to changes in cloud cover (represented in ERA-40).

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Miscellaneous

http://www.nature.com/articles/nclimate2872.epdf

Most regions of the world ocean are warmer in the near-surface [0-700 m] layer than in previous decades, by over 1° C in some places. A few areas, such as the eastern Pacific from Chile to Alaska, have cooled by as much as 1° C, yet overall the upper ocean has warmed by nearly 0.2° C globally since the mid-twentieth century.

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http://www.sciencedirect.com/science/article/pii/S0012821X16000388

During the past five million yrs, benthic δ18O records indicate a large range of climates, from warmer than today during the Pliocene Warm Period to considerably colder during glacials. Antarctic ice cores have revealed Pleistocene glacial–interglacial CO 2 variability of 60–100 ppm, while sea level fluctuations of typically 125 m are documented by proxy data. … Our model shows CO 2 concentrations of 300 to 470 ppm during the Early Pliocene [5 million years ago]. Furthermore, we simulate strong CO 2 variability during the Pliocene and Early Pleistocene. These features are broadly supported by existing and new δ11B-based proxy CO 2 data, but less by alkenone-based records. The simulated concentrations and variations therein are larger than expected from global mean temperature changes. Our findings thus suggest a smaller Earth System Sensitivity than previously thought. This is explained by a more restricted role of land ice variability in the Pliocene. The largest uncertainty in our simulation arises from the mass balance formulation of East Antarctica, which governs the variability in sea level, but only modestly affects the modeled CO 2 concentrations.

Ice Sheets, Sea Ice, Antarctic, Arctic

http://onlinelibrary.wiley.com/doi/10.1002/2015JD024247/full

Attributing the observed climate changes to relevant forcing factors is critical to predicting future climate change scenarios. Precipitation observations in the Southern Hemisphere (SH) indicate an apparent moistening pattern over the extratropics during the time period 1979 to 2013. To investigate the predominant forcing factor in triggering such an observed wetting climate pattern, precipitation responses to four climatic forcing factors, including Antarctic ozone, water vapour, sea surface temperature (SST), and carbon dioxide, were assessed quantitatively in sequence through an inductive approach. … Quantified differential contribution with respect to those climatic forcing factors may explain why the observed austral extratropical moistening pattern is primarily driven by the Antarctic ozone depletion, while mildly modulated by the cooling effect of equatorial Pacific SST and the increased greenhouse gases, respectively.

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http://science.sciencemag.org/content/351/6273/590

Recent peripheral thinning of the Greenland Ice Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the ice sheet’s radiostratigraphy, ice flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The ice sheet’s dynamic response to the decreasing proportion of softer ice from the last glacial period and the deglacial collapse of the ice bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland Ice Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its mass balance from altimetry.

http://www.eurekalert.org/pub_releases/2016-02/aaft-gis020116.php

“[T]he interior of the GrIS is flowing 95% slower now than it was on average during the Holocene.”

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http://www.sciencedirect.com/science/article/pii/S0967064516300108

In late winter-early spring 2012, the second Sea Ice Physics and Ecosystems Experiment (SIPEX II) was conducted off Wilkes Land, East Antarctica, onboard R/V Aurora Australis. The sea-ice conditions were characterized by significantly thick first-year ice and snow, trapping the ship for about 10 days in the near coastal region. The deep snow cover was particularly remarkable, in that its average value of 0.45 m was almost three times that observed between 1992 and 2007 in the region. … Based on these results, we deduce that lower loss of snow into leads was probably responsible for the extraordinary snow in 2012. Statistical analysis and satellite images suggest that the reduction in loss of snow into leads is attributed to rough ice surface associated with active deformation processes and larger floe size due to sea-ice expansion. This highlights the importance of snow-sea ice interaction in determining the mean snow depth on Antarctic sea ice.

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http://link.springer.com/article/10.1007/s00382-015-2907-4

We present climate and surface mass balance (SMB) of the Antarctic ice sheet (AIS) as simulated by the global, coupled ocean–atmosphere–land Community Earth System Model (CESM) with a horizontal resolution of ∼1∘ in the past, present and future (1850–2100). CESM correctly simulates present-day Antarctic sea ice extent, large-scale atmospheric circulation and near-surface climate, but fails to simulate the recent expansion of Antarctic sea ice. The present-day Antarctic ice sheet SMB equals 2280±131 Gtyear−1, which concurs with existing independent estimates of AIS SMB. When forced by two CMIP5 climate change scenarios (high mitigation scenario RCP2.6 and high-emission scenario RCP8.5), CESM projects an increase of Antarctic ice sheet SMB of about 70 Gtyear−1 per degree warming. This increase is driven by enhanced snowfall, which is partially counteracted by more surface melt and runoff along the ice sheet’s edges. This intensifying hydrological cycle is predominantly driven by atmospheric warming, which increases (1) the moisture-carrying capacity of the atmosphere, (2) oceanic source region evaporation, and (3) summer AIS cloud liquid water content.

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http://www.sciencedirect.com/science/article/pii/S0921818115301867

Prydz Bay is one of the largest embayments on the East Antarctic coast and it is the discharge point for approximately 16% of the East Antarctic Ice Sheet. … The compiled geological data extend the relative sea-level curve for this region to 11,258 cal yr BP and include new constraints based on abandoned penguin colonies, new isolation basin data in the Vestfold Hills, validation of a submarine relative sea-level constraint in the Rauer Islands and recalibrated radiocarbon ages at all sites dating from 12,728 cal yr BP. The field data show rapid increases in rates of relative sea level rise of 12–48 mm/yr between 10,473 (or 9678) and 9411 cal yr BP in the Vestfold Hills and of 8.8 mm/yr between 8882 and 8563 cal yr BP in the Larsemann Hills. The relative sea-level high stands of ≥ 8.8 m from 9411 to after 7564 cal yr BP (Vestfold Hills) and ≥ 8 m at 8563 and 7066 cal yr BP (Larsemann Hills) are over-predicted by some of the glacial isostatic adjustment models considered here, suggesting that assumptions relating to the magnitude and timing of regional ice loss since the Last Glacial Maximum may need revising. In the Vestfold Hills and Rauer Islands the final deglacial sea-level rise was almost exactly cancelled out by local rebound between 9411 and 5967 cal yr BP and this was followed by a near exponential decay in relative sea-level.

Ocean Acidification

http://onlinelibrary.wiley.com/doi/10.1111/gcb.13223/abstract

Near the vent site, the urchins experienced large daily variations in pH (> 1 unit) andpCO 2 (> 2000 ppm) and average pH values (pH T 7.73) much below those expected under the most pessimistic future emission scenarios. Growth was measured over a 17-month period using tetracycline tagging of the calcareous feeding lanterns. Average-sized urchins grew more than twice as fast at the vent compared with those at an adjacent control site, and assumed larger sizes at the vent compared to the control site and two other sites at another reef near-by. … Thus, urchins did not only persist but actually ‘thrived’ under extreme CO 2 conditions.

Greening of the Planet, Crops

http://www.nature.com/articles/srep20716

Elevated CO 2 as a driver of global dryland greening

While recent findings based on satellite records indicate a positive trend in vegetation greenness over global drylands, the reasons remain elusive. We hypothesize that enhanced levels of atmospheric CO 2 play an important role in the observed greening through the CO 2 effect on plant water savings and consequent available soil water increases. Meta-analytic techniques were used to compare soil water content under ambient and elevated CO 2 treatments across a range of climate regimes, vegetation types, soil textures and land management practices. Based on 1705 field measurements from 21 distinct sites, a consistent and statistically significant increase in the availability of soil water (11%) was observed under elevated CO 2 treatments in both drylands and non-drylands, with a statistically stronger response over drylands (17% vs. 9%). Given the inherent water limitation in drylands, it is suggested that the additional soil water availability is a likely driver of observed increases in vegetation greenness.