Partners

A reconstruction of past spring temperatures was analysed and compared to long-term records of the North Atlantic Oscillation (NAO) and sunspots. This palaeoclimate reconstruction, built previously using multiple proxy evidence of historical and natural sources from southwest Finland, explained approx. 70% of the instrumental temperature variance over a spring season (February–June) and covered the time period from 1750 to the present. Correlations between the NAO and sunspots appear markedly high and, based on Monte Carlo tests, statistically significant (p < 0.01) since around 1925. Correlation between sunspots and temperatures appeared notably high over the past 50 years, but this association could not be confirmed by the significance test. Correlations between the NAO and temperatures were high and statistically significant. However, the pre-1860s NAO–temperature correlations were lower than the correlations after that date. Previous studies have emphasized the possibility of enhanced solar forcing on NAO variability over the past 30–40 years broadly operative on decadal scales (with so far unresolved explanatory mechanisms). Our results correlate with this view to a statistically significant extent (p < 0.01) in the context of the past two centuries of regional climate variability. The NAO–temperature correlations were clearly stronger than the correlations between sunspots and temperatures. Moreover, the correlations were stronger between decadally filtered records. Consequently, the potential solar forcing on regional temperatures may have operated on decadal scales and been augmented by the NAO–temperature association.
http://www.sciencedirect.com/science/article/pii/S0031018212000867

Several studies indicate that changes in solar activity may have driven Holocene subtropical monsoon variability on decadal and centennial timescales, but the strength and nature of this link remains debated. In this study, we combine a recent mapping of the Holocene solar-cycle activity with four subtropical speleothem δ18O records, which allows a strong test of the link between solar activity, monsoon activity (or intensity), and the hydrological cycle. This is possible because the speleothem δ18O records mainly reflect changes in local rainfall composition, which is controlled by changes in total moisture loss along the atmospheric transport path and monsoon intensity. We find that the spectral density distributions of the speleothem records exhibit particularly significant ~210 yr cyclicities that tend to coincide in time with the three Suess solar-cycle bursts, i.e. intervals around 1850–3200 BP, 4500–5700 BP, and 7750–8850 BP when the ~210 yr solar cycle was particularly strong. The speleothems from Dongge Cave (China) and Sofular Cave (Turkey) appear to have recorded all three Suess bursts, whereas the speleothems from Heshang Cave (China) and Pink Panther Cave (southwestern USA) only recorded the first and last Suess bursts, and the middle Suess burst, respectively. The temporal relationship between the Suess solar cycle and particularly significant 210 yr oscillations in the speleothem δ18O records therefore supports the notion that solar variability played a significant role in driving centennial-scale changes in the hydrological cycle in the subtropics during the Holocene.
http://hol.sagepub.com/content/early/2011/11/28/0959683611427331.abstract?rss=1

1] We analyze the periods 1878–1944 and 1944–2008. The quasi-stationary wave in the North Atlantic region was stronger and the baroclinity steeper in 1878–1944 than in 1944–2008. The North Atlantic Oscillation Index—as defined by the Climate Research Unit, University of East Anglia—was higher in the former period too. We illustrate these statements by maps of sea level pressure and air temperature at the surface. The long-term trends in the North Atlantic Oscillation Index are linked to the trend in sunspot number such that when, in the mean, the sunspot numbers were high (Gleissberg maxima) the trends in the two quantities were parallel; and when the mean sunspot numbers were low (Gleissberg minima) the trends in the North Atlantic Oscillation Index and sunspots were opposite. We find the connections between the trends statistically significant, and we infer that the level of solar activity played a role in the trends of the past two centuries in the North Atlantic region. However, we cannot as yet provide a mechanism linking the solar trends to those in the atmosphere and ocean, but as a step toward an explanation, the equator to pole temperature gradient is steeper in a Gleissberg minimum than in a maximum.
http://onlinelibrary.wiley.com/doi/10.1029/2012JD017502/abstract

Variability of rainfall and temperature (1912–2008) parameters measured from Santa Maria (29°41′S, 53°48′W) and their connections with ENSO and solar activity

In this work, we analyze the long term variability of rainfall and temperature (1912–2008) of Santa Maria (29°S, 53°W) and its possible connection with natural influences such as solar activity and ENSO. Temperature and rainfall present similar frequencies as revealed by spectral analyses. This analysis shows a large number of short periods between 2–8 years and periods of 11.8–12.3, 19.1–21.0, and 64.3–82.5 years. The cross correlation for rainfall and temperature versus Southern Oscillation Index (SOI) have higher cross-power around 2–8 yr. Rainfall and temperature versus sunspot number (Rz) showed higher cross-power around the 11-yr solar cycle period. A high and continuous cross correlation was observed for Rz-22 yr versus rainfall and temperature. Furthermore, the power between 22-yr solar cycle and meteorological parameters was higher than that obtained with the 11-yr solar cycle, suggesting that the effect of Hale cycle on climate may be stronger than the Schwabe cycle effect. These results indicate that the variability of rainfall and temperature is closely related to the variation of the Southern Oscillation Index and solar activity, and that the El Nino Southern Oscillation and solar activity probably play an important role in the climate system over Southern Brazil.
http://www.sciencedirect.com/science/article/pii/S1364682611003452

Temporal derivative of Total Solar Irradiance and anomalous Indian summer monsoon: An empirical evidence for a Sun–climate connection

Identifying the pattern of natural climate variability is of immense importance to delineate the effects of anthropogenic climate changes. Global and regional climates are suspected to vary, in unison or with delays, with the Total Solar Irradiance (TSI) at decadal to centennial timescales. Here we show that the Indian summer monsoon rainfall correlates well with the temporal derivative of TSI on multi-decadal timescales. This linkage between the temporal derivative of TSI and the Indian summer monsoon is tested and corroborated both for the instrumental period (1871–2006) and for the last ∼300 years using a speleothem δ18O record representing rainfall in southwestern India. Our analyses indicate that anomalous dry periods of the Indian monsoon are mostly coincident with negative TSI derivative. This study thus demonstrates the potential of ‘TSI derivative’ as an important indicator of natural monsoon variability on an interdecadal timescale.
http://www.sciencedirect.com/science/article/pii/S1364682611001726

Multifractal Detrended Cross-Correlation Analysis of Sunspot Numbers and River Flow Fluctuations

We use the Detrended Cross-Correlation Analysis (DCCA) to investigate the influence of sun activity represented by sunspot numbers on one of the climate indicators, specifically rivers, represented by river flow fluctuation for Daugava, Holston, Nolichucky and French Broad rivers. The Multifractal Detrended Cross-Correlation Analysis (MF-DXA) shows that there exist some crossovers in the cross-correlation fluctuation function versus time scale of the river flow and sunspot series. One of these crossovers corresponds to the well-known cycle of solar activity demonstrating a universal property of the mentioned rivers. The scaling exponent given by DCCA for original series at intermediate time scale, (12−24)≤s≤130 months, is λ=1.17±0.04 which is almost similar for all underlying rivers at 1σconfidence interval showing the second universal behavior of river runoffs. To remove the sinusoidal trends embedded in data sets, we apply the Singular Value Decomposition (SVD) method. Our results show that there exists a long-range cross-correlation between the sunspot numbers and the underlying streamflow records. The magnitude of the scaling exponent and the corresponding cross-correlation exponent are λ∈(0.76,0.85) and γ×∈(0.30,0.48), respectively. Different values for scaling and cross-correlation exponents may be related to local and external factors such as topography, drainage network morphology, human activity and so on. Multifractal cross-correlation analysis demonstrates that all underlying fluctuations have almost weak multifractal nature which is also a universal property for data series. In addition the empirical relation between scaling exponent derived by DCCA and Detrended Fluctuation Analysis (DFA), λ≈(hsun+hriver)/2 is confirmed.
http://arxiv.org/abs/0908.0132

Holocene hydrological changes in south-western Mediterranean as recorded by
lake-level fluctuations at Lago Preola, a coastal lake in southern Sicily, Italy

Un studiu foarte important. (clima ultimii 11 000 ani)
http://www.botany.unibe.ch/paleo/publications/reprints/QuatSciRev_30_2459.pdf

Abrupt Holocene Sunt prost and potential response to solar forcing in western Canada

Several abrupt climate events during the Holocene, including the widely documented oscillation at 8.2 thousand years before present (ka), are attributed to changes in the North Atlantic thermohaline circulation. Additional mechanisms, such as interactions between atmospheric circulation, ice-sheet dynamics, and the influence of solar irradiance, also have been proposed to explain abrupt climatic events, but evidence remains elusive. This study presents evidence from multi-proxy analyses on the Holocene sediments of Eleanor Lake, interior British Columbia. Climatic inferences from our decadal-resolution record of biogenic silica (BSi) abundance are supported by changes in diatom and pollen assemblages from the same core and correlations with existing regional climate records. The BSi record reveals abrupt and persistent climatic shifts at 10.2, 9.3, and 8.5 ka, the latter two of which are coeval with major collapses of the Laurentide Ice Sheet. The record also reveals a short-term cooling at 8.2 ka that is distinct from the 8.5 ka event and similar in magnitude to several other late-Holocene coolings. BSi is correlated with solar-irradiance indices (r = 0.43–0.61), but the correlation is opposite in sign to that expected from direct solar forcing and weakens after 8 ka. Possible mechanisms causing the abrupt and persistent climate changes of the early Holocene include 1) sudden losses of ice and proglacial lake extent, causing a shift in the meridional structure of atmospheric circulation, 2) a possible link between solar minima and El Niño-like conditions that are correlated with warm spring temperature in interior British Columbia, and 3) the influence of solar irradiance variability on the position of the polar jet, possibly via effects on the strength of the glacial anticyclone.

http://www.sciencedirect.com/science/article/pii/S0277379111000758

A new approach to the long-term reconstruction of the solar
irradiance leads to large historical solar forcing

(o reconstructie a TSI pentru ultimii 7 000 de ani.)
http://www.aanda.org/articles/aa/pdf/2011/05/aa16173-10.pdf

Long-term solar activity as a controlling factor for global warming in the 20th century

Such high-resolution indirect data on solar activity as the 14C and 10Be cosmogenic isotopes have been considered. The long-term solar activity cyclicity during the last millennium with periods of approximately 90 and 210 years, which can be related to substantial climatic warming and cooling events in this millennium, has been established based on an analysis of these data. It has been indicated that long-term recent climate warming can result from the effect of the ∼90- and ∼210-year solar cycles on the climatic system, which is characterized by the nonlinear dynamics.

http://link.springer.com/article/10.1134%2FS0016793209080477

Impact of variations in solar activity on hydrological decadal patterns in northern Italy

Using spectral and statistical analyses of discharges and basin average precipitation rates acquired over the Po River since the early 1800s, we investigate the impact of variations in solar activity on hydrological decadal patterns over northern Italy. Wet and dry periods appear to alternate in accordance with polarized sunspot cycles. Intriguingly, a solar signature on Po River discharges is detected to be highly significant since the late 1800s, before the onset of sunspots hyperactivity established by the middle 1900s. In particular, observed hydrological patterns over northern Italy are significantly correlated, under periods of quiet sunspot activity, with parameters characterizing the Sun's orbital motion, specifically with the time derivative of the solar angular momentum (τ) which is thought to modulate the strength of the solar wind and sunspot dynamics under weak sunspot activity. The North Atlantic Oscillation (NAO) is detected as potential link between the Sun and Po River discharges, since it is significantly correlated with both solar activity and the decadal variability in the north Italian climate. In particular, positive (negative) NAO anomalies, which are associated with comparatively lower (higher) Po River discharges, are assessed to alternatively correlate at decadal timescales either with τ or with the Earth's geomagnetic activity (GA), which closely follows sunspot activity. This changing correlation seems to be regulated by the strength of sunspot activity: under periods of quiet sunspot activity, a weakening of the GA-NAO connection and a reinforcement of the τ-NAO connection is observed. In this sense, the strength of solar activity apparently modulates the connection between the NAO and Po River discharges.

http://onlinelibrary.wiley.com/doi/10.1029/2007JD009157/abstract

Corelatii intre NAO si zapada

DECADAL VARIABILITY OF RUSSIAN WINTER SNOW
ACCUMULATION AND ITS ASSOCIATIONS WITH ATLANTIC SEA
SURFACE TEMPERATURE ANOMALIES

"The strength of the NAO is linked directly to winter surface air
temperature and precipitation anomalies over northern Eurasia"

http://onlinelibrary.wiley.com/doi/10.1002/1097-0088(20001130)20:14%3C1709::AID-JOC573%3E3.0.CO;2-6/pdf


SNOW COVER IN EASTERN EUROPE IN RELATION TO TEMPERATURE,
PRECIPITATION AND CIRCULATION

The basic characteristics of snow cover occurrence in eastern Europe are described. For each month from October to
May the range of ‘active’ snow-cover areas in Europe was determined. The boundary criterion for ‘active’ regions
was adopted as snow-cover probability of between 10 and 90%. The correlation coefficients between the snow-cover
characteristics (number of days with snow cover and its monthly mean depth) and other climatic variables (temperature
and precipitation) were calculated. A strong positive correlation between the annual number of days with snow cover and
the annual number of days with mean temperature <0°C was discovered for most parts of the study area. A negative
correlation between the monthly number of days with snow cover and monthly mean temperature was found and its
spatial distribution was analysed. A positive correlation between snow depth and precipitation appeared significant only
in some areas. The influence of atmospheric circulation, expressed by North Atlantic oscillation (NAO) index values, on
snow cover in the particular months was analysed. The correlation between the number of days with snow cover and the
NAO index is large and statistically significant only in central Europe and it becomes insignificant to the east of 30° λ
E. High values are noted only in the winter months. In autumn and spring, when the range of the ‘active’ areas moves
to the east and the NAO becomes weak, the correlation is very small.
http://onlinelibrary.wiley.com/doi/10.1002/joc.1014/pdf
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Arctic warming, atmospheric blocking and
cold European winters in CMIP5 models

"In this section we analyse the surface air temperature from the
12 models to determine if there is a relationship between Arctic
warming and the occurrence of cold winter anomalies over
Europe.We follow the approach of YC in defining a cold winter
month (CWM) to occur when the surface air temperature
averaged over the central European region (10–30E, 45–55N)
falls below the climatological mean of the present day period"
http://iopscience.iop.org/1748-9326/9/1/014002/pdf/1748-9326_9_1_014002.pdf
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SNOW COVER IN WESTERN POLAND AND MACRO-SCALE
CIRCULATION CONDITIONS

"The aim of the study was to find out the connection between the nature of winters in the western part of Poland (excluding
the Sudety mountains) and the fluctuation in the atmospheric circulation in the North Atlantic region determined by the
North Atlantic Oscillation (NAO) index. An attempt was made to establish the correlation between the NAO index
and specific meteorological parameters in Poznan. The strongest positive correlation was obtained for the mean winter ´
temperature (December–March) and strong negative correlation was found for the number of days with snow cover. Winter
precipitation in Poznan was least associated with the NAO. The correlation coefficient was small and not significant. In ´
the next stage of the study, the area of western Poland was examined; however, only one parameter, i.e. the number of
days with snow cover, was taken into consideration. At each of 29 stations distributed in the study area the number of
days with snow cover was proved to be strongly negatively correlated with the NAO index. Finally, the frequency of
air flow directions was taken into consideration and their association with the NAO was examined. A strong negative
correlation was obtained for the frequency of northeasterly and easterly air flow directions and a strong positive correlation
was calculated for the frequency of westerly and northwesterly airflow directions. Such findings are consistent with the
westerly flow of air masses during the positive phase and with the northerly and easterly flows during the negative phase.
The results lead to the conclusion that the positive phase of the NAO causes mild and less snowy winters, whereas
the negative phase increases the probability of severe and snowy winters in western Poland."
http://onlinelibrary.wiley.com/doi/10.1002/joc.752/pdf
*****
SPRING NORTHWARD RETREAT OF EURASIAN SNOW COVER RELEVANT
TO SEASONAL AND INTERANNUAL VARIATIONS OF ATMOSPHERIC
CIRCULATION
EURASIAN SNOW COVER AND ATMOSPHERIC CIRCULATION
http://onlinelibrary.wiley.com/doi/10.1002/joc.903/pdf

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Freshwater and brine behaviors in the Arctic Ocean deduced
from historical data of D18O and alkalinity (1929–2002 A.D.)

"two circulation
regimes of wind-driven circulation in the modeled Arctic
Ocean: cyclonic and anticyclonic regimes, which are the
response of the ocean to atmospheric fluctuations. Our
results have been divided into two groups of cyclonic years
(1953 – 1957, 1964 – 1971, 1980 – 1983, 1989 – 1996, and
2001– 2002) and anticyclonic years (1946 – 1952, 1958–
1963, 1972 – 1979, 1984 – 1988, and 1997– 2000) following
Proshutinsky and Johnson [1997]"
http://onlinelibrary.wiley.com/doi/10.1029/2004JC002793/pdf