summer temperature patterns over europe a reconstruction from 1750 a d based on maximum latewood density indices of conifers abstract temperature variations over europe are reconstructed for a 6 month summer season from april to september for the period 1750 1850 using a network of maximum latewood density chronologies of coniferous trees around 44 of the variance of the whole temperature grid was explained in calibration independent verification indicates that over the reconstruction period the explained variance averaged over the whole grid should lie in the range 30 to 35 the reconstructions are better in the north of the region about 50 explained temperature variance based on comparison with independent climate data than in the south below 20 the temperature recontructions indicate cooler summers over europe from 1812 to 1816 and during the 1830s the summers of the 1820s were the warmest reconstructed decadal variations occur on a regional scale but no similar periods of anomalously cooler or warmer summers occurred between 1750 and 1810 throughout europe

a 352 year record of summer temperature reconstruction in the western tianshan mountains china as deduced from tree ring density three robust tree ring density chronologies were developed for the western tianshan mountains of northwestern china the chronologies were significantly correlated and form a regional chronology gld the gld had significant and positive correlations with temperature of warm seasons based on this relationship the mean minimum temperatures of may to august were reconstructed using the gld chronology for the period ad 1657 to 2008 the temperature reconstruction exhibited temperature patterns on interannual to centennial timescales and showed that the end of the 20th century is the warmest period in the past 352 years the reconstructed temperature variation has a teleconnection with large scale atmospheric oceanic variability and captures long and broad scale regional climatic variations

record of volcanism since 7000 b c from the gisp2 greenland ice core and implications for the volcano climate system sulfate concentrations from continuous biyearly sampling of the gisp2 greenland ice core provide a record of potential climate forcing volcanism since 7000 b c although 85 percent of the events recorded over the last 2000 years were matched to documented volcanic eruptions only about 30 percent of the events from 1 to 7000 b c were matched to such events several historic eruptions may have been greater sulfur producers than previously thought there are three times as many events from 5000 to 7000 b c as over the last two millennia with sulfate deposition equal to or up to five times that of the largest known historical eruptions this increased volcanism in the early holocene may have contributed to climatic cooling

cold decade ad 1810 1819 caused by tambora 1815 and another 1809 stratospheric volcanic eruption climate records indicate that the decade of ad 1810 1819 including the year without a summer 1816 is probably the coldest during the past 500 years or longer and the cause of the climatic extreme has been attributed primarily to the 1815 cataclysmic tambora eruption in indonesia but the cold temperatures in the early part of the decade and the timing of the tambora eruption call into question the real climatic impact of volcanic eruptions here we present new evidence based on sulfur isotope anomaly 33s a unique indicator of volcanic sulfuric acid produced in the stratosphere and preserved in polar snow and on the precise timing of the volcanic deposition in both polar regions that another large eruption in 1809 of a volcano is also stratospheric and occurred in the tropics the tambora eruption and the undocumented 1809 eruption are together responsible for the unusually cold decade

global surface temperature responses to major volcanic eruptions the impacts of pollution resulting from large explosive volcanic eruptions on the atmospheric heat budget and planetary albedo are not in doubt1 2 however the effects of volcanic aerosols on the surface climate are less clear and still controversial3 4 in a previous study5 it was shown that significant surface cooling occurs over the landmasses of the northern hemisphere in the first few months after a major eruption in that hemisphere here we extend that work using new surface air temperature compilations based on land and marine data6 for both the northern and southern hemispheres our results indicate that major northern hemisphere eruptions have an immediate effect on the northern hemisphere average surface temperature but little or no effect on the southern hemisphere average southern hemisphere eruptions affect both southern and northern hemisphere temperatures after a lag of between six months and a year

frost rings in trees as records of major volcanic eruptions new data about climatically effective volcanic eruptions during the past several thousand years may be contained in frost damage zones in the annual rings of trees there is good agreement in the timing of frost events and recent eruptions and the damage can be plausibly linked to climatic effects of stratospheric aerosol veils on hemispheric and global scales the cataclysmic proto historic eruption of santorini thera in the aegean is tentatively dated to 1628 26 bc from frost ring evidence

tree ring evidence of the widespread effects of explosive volcanic eruptions tree ring evidence from 97 sites over north america and europe are used to develop a chronology of widespread cool summers since 1600 averaging annual maximum density information from the chronologies provides an index that correlates with northern hemisphere summer temperatures to 0 44 over 1851 1975 a number of the extreme low density years occur in both north america and europe suggesting a common response to high frequency forcing the analysis was repeated with ring width information but the results are markedly less coherent of the five common extreme low density years 1601 1641 1669 1699 and 1912 four are known to be coincident with the year or year following major volcanic eruptions other extreme low density indices in the continental series are also clear coincident with known volcanoes the density indices clearly demonstrate great potential for quantifying the climate effectiveness and perhaps establishing precise calendar dates of large explosive volcanoes 30 refs

sulfur budget and global climate impact of the a d 1835 eruption of cosiguina volcano nicaragua large explosive volcanic eruptions can inject massive amounts of sulfuric gases into the earth s atmosphere and in so doing affect global climate the january 1835 eruption of cosiguina volcano nicaragua ranks among the americas largest and most explosive historical eruptions but whether it had effects on global climate remains ambiguous new petrologic analyses of the cosiguina deposits reveal that the eruption released enough sulfur to explain a prominent ca ad 1835 sulfate anomaly in ice cores from both the arctic and antarctic a compilation of temperature sensitive tree ring chronologies indicates appreciable cooling of the earth s surface in response to the eruption consistent with instrumental temperature records we conclude that this eruption represents one of the most important sulfur producing events of the last few centuries and had a sizable climate impact rivaling that of the 1991 eruption of mount pinatubo

evidence for a volcanic cooling signal in a 335 year coral record from new caledonia although volcanic cooling events have been detected in tree ring records their occurrence in marine records has received much less attention herein we report results from a 335 year oxygen isotope record 1657 1992 from a new caledonia coral indicating that as many as 16 interannual scale cooling events occur within 1 year of a volcanic eruption as determined by ice core records there are also pentadal decadal scale cooling events beginning in 1675 1813 and 1903 that immediately postdate volcanic eruptions however the interannual correspondences are complicated by the fact that some of the cooling events also coincide with el ninos which cause cooling in this part of the western south pacific if our conclusions are substantiated by further work occurrence of distinct volcanic cooling signals may enable refinement of coral chronologies by use of the event stratigraphic approach with the most promising correlation horizons being associated with the following eruptions 1808 unknown 1813 1821 several eruptions 1835 coseguina 1883 krakatau and possibly 1963 agung

consistent decrease in north atlantic tropical cyclone frequency following major volcanic eruptions in the last three centuries injection of sulphate aerosols into the stratosphere following major volcanic eruptions alters global climate through the absorption and scattering of solar radiation one proposed consequence is a decrease in north atlantic tropical cyclone tc activity as was observed following the el chichon 1982 and mount pinatubo 1991 eruptions we test this relationship using documentary and proxy reconstructions of major volcanic eruptions and tc frequency in the north atlantic basin over the last three centuries we find a consistent reduction in the number of tcs formed during the 3 years following major eruptions compared to the preceding 3 years including after eruptions located at northern high latitudes our findings suggest that low latitude eruptions reduce atlantic tc frequency by decreasing local sea surface temperatures whereas the mechanisms for the decrease in tc frequency following high latitude eruptions are less clear and attribution is hampered by poor identification of these events

solar and volcanic fingerprints in tree ring chronologies over the past 2000 years abstract the sun is the main driver of earth s climate yet the sun s role in forcing decadal to centennial climate variations has remained controversial especially in the context of understanding contributions of natural climate forcings to continuing global warming to properly address long term fingerprints of solar forcing on climate long term very high resolution globally distributed climate proxy records are necessary in this study we compile and evaluate a near global collection of annually resolved tree ring based climate proxies spanning the past two millennia we statistically assess these records in both the time and frequency domains for solar forcing i e total solar irradiance tsi and climate variability with emphasis on centennial time scales analyses in the frequency domain indicate significant periodicities in the 208 year frequency band corresponding to the devries cycle of solar activity additionally results from superposed epoch analysis sea point toward a possible solar contribution in the temperature and precipitation series however solar climate associations remain weak with for example no clear linkage distinguishable in the southwestern united states drought records at centennial time scales other forcing factors namely volcanic activity appear to mask the solar signal in space and time to investigate this hypothesis we attempted to extract volcanic signals from the temperature proxies using a statistical modelling approach wavelet analysis of the volcanic contribution reveals significant periodicities near the devries frequency during the little ice age lia this remarkable and coincidental superposition of the signals makes it very difficult to separate volcanic and solar forcing during the lia nevertheless the volcano free temperature records show significant periodicities near the devries periodicity during the entire past 1500 years further pointing to solar mechanisms and emphasising the need for solar related studies in the absence of strong multi decadal volcanic forcing

a 220 year continuous record of volcanic h2so4 in the antarctic ice sheet continuous h2so4 profiles observed in snow from several antarctic locations reveal four major volcanic events of the past two centuries agung krakatoa tambora and another large scale event not recorded historically acid deposition and interhemispheric distribution mechanisms are quantified and then used to obtain an order of magnitude estimate for the h2so4 emissions from these eruptions

the volcanic signal in surface temperature observations abstract climate records of the past 140 years are examined for the impact of major volcanic eruptions on surface temperature after the low frequency variations and el nino southern oscillation signal are removed it is shown that for 2 years following great volcanic eruptions the surface cools significantly by 0 1 0 2 c in the global mean in each hemisphere and in the summer in the latitude bands 0 30 s and 0 30 n and by 0 3 c in the summer in the latitude band 30 30 60 n by contrast in the first winter after major tropical eruptions and in the second winter after major high latitude eruptions north america and eurasia warm by several degrees while northern africa and southwestern asia cool by more than 0 5 c because several large eruptions occurred at the same time as enso events the warming produced by the enso masked the volcanic cooling during the first year after the eruption the timescale of the enso response is only 1 year while the volcanic response timescale is 2 years so the coo

boreal temperature variability inferred from maximum latewood density and tree ring width data wrangell mountain region alaska abstract variations in both width and density of annual rings from a network of tree chronologies were used to develop high resolution proxies to extend the climate record in the wrangell mountain region of alaska we developed a warm season july september temperature reconstruction that spans a d 1593 1992 based on the first eigenvector from principal component analysis of six maximum latewood density mxd chronologies the climate tree growth model accounts for 51 of the temperature variance from 1958 to 1992 and shows cold in the late 1600s early 1700s followed by a warmer period cooling in the late 1700s early 1800s and warming in the 20th century the 20th century is the warmest of the past four centuries several severely cold warm seasons coincide with major volcanic eruptions the first eigenvector from a ring width rw network based on nine chronologies from the wrangell mountain region a d 1550 1970 is correlated positively with both reconstructed and recorded northern hemisphere temperatures rw shows a temporal history similar to that of mxd by increased growth warmer and decreased growth cooler intervals and trends after around 1970 the rw series show a decrease in growth while station data show continued warming which may be related to increasing moisture stress or other factors both the temperature history based on mxd and the growth trends from the rw series are consistent with well dated glacier fluctuations in the wrangell mountains and some of the temperature variations also correspond to variations in solar activity

tree ring evidence for climatically effective volcanic eruptions abstract ringwidth variations from temperature sensitive upper timberline sites in the sierra nevada show a marked correspondence to the decadal pattern of volcanic sulfate aerosols recorded in a greenland ice core acidity profile and a significant negative growth response to individual explosive volcanic events the appearance of single events in the mid latitude tree ring record in connection with ice core evidence from the arctic and historical records from the mediterranean indicates that the majority of these events represent climatically effective volcanic eruptions producing temperature decreases on the order of 1 c for up to 2 yr after the initial eruption clusters of climatically effective volcanic events may serve as a trigger to glaciation and are consistently associated with lowered ringwidths and late holocene glacier advance in the sierra nevada the tree ring record strongly suggests forcing of solar radiation receipt and temperatures by increased volcanic aerosols especially during the recess peak advances and matthes little ice age advances from 1400 to 1850 a d intervals with an absence of significant volcanic aerosol production or historically documented eruptive activity correspond to intervals of significantly increased indexed ringwidth values minimal numbers of severe annual negative ringwidth anomalies and an absence of glacial deposits in the southern sierra nevada

complexities of the san andreas fault near san gorgonio pass implications for large earthquakes 1 geologic relationships and patterns of crustal seismicity constrain the three dimensional geometry of the active portions of san andreas fault zone near san gorgonio pass southern california within a 20 km wide contractional stepover between two segments of the fault zone the san bernardino and coachella valley segments folds and dextral reverse and dextral normal faults form an east west belt of active structures the dominant active structure within the stepover is the san gorgonio pass garnet hill faults a dextral reverse fault system that dips moderately northward within the hanging wall block of the san gorgonio pass garnet hill fault system are subsidiary active dextral and dextral normal faults these faults relate in complex but understandable ways to the strike slip faults that bound the stepover the pattern of crustal seismicity beneath these structures includes a 5 8 km high east west striking step in the base of crustal seismicity which corresponds to the downdip limit of rupture of the 1986 north palm springs earthquake we infer that this step has been produced by slip on the linked san gorgonio pass garnet hill coachella valley banning sgp gh cvb fault this association enables us to construct a structure contour map of the fault plane the large step in the base of seismicity downdip from the sgp gh cvb fault system probably reflects a several kilometers offset of the midcrustal brittle plastic transition u th he thermochronometry supports our interpretation that this south under north thickening of the crust has created the region s 3 km of topographic relief we conclude that future large earthquakes generated along the san andreas fault in this region will have a multiplicity of mostly specifiable sources having dimensions of 1 20 km two tasks in seismic hazard evaluation may now be attempted with greater confidence first the construction of synthetic seismograms that make useful predictions of ground shaking and second theoretical investigations of the role of this complexity in retarding the propagation of future seismic ruptures

an improved approach for evaluating the time dependent stability of colluvial landslides during intense rainfall the paper presents an improved analytical approach for evaluating the time dependent stability of colluvial landslides during intense rainfall infiltration the approach comprises two steps first to simulate rainfall infiltration and then to compute the safety factor in terms of the irregularity of the natural landslide surface in implementation of the method the landslide is divided into several soil slices with approximately straight sides each single slice is regarded as a finite slope so that the infiltration formula and safety factor can be deduced the infiltration formula is derived with combination of the green ampt model and mass conservation law considering seepage perpendicular and parallel to slope surface simultaneously in the modified infiltration model both size effect and angle effect are vividly observed in the process of rainfall infiltration into the finite slope while the former of which is not presented in the original green ampt model the safety factor is computed using the limit equilibrium method with the influence of infiltrating water on the shear strength gravity and seepage force of soil slices considered by case study of the shuping landslide in three gorges decline in the safety factor and the decrease in the tendency are definite specifically under the rainfall intensity of 50 mm h the failure of shuping landslide is most likely to occur at the time of 102 h in addition the results highlight shallow failure along the wetting front under intense rainfall