Frequency, magnitude and character of hyperthermal events at the onset of the Early Eocene Climatic Optimum
Summary: Several episodes of global warming took place during greenhouse conditions in the early Eocene and are recorded in deep-sea sediments. The stable carbon and oxygen isotope records are used to investigate the magnitude of six of these events describing their effects on the global carbon cycle and the associated temperature response. Findings indicate that these events share a common nature and hint to the presence of multiple sources of carbon release.
Clim. Past, 11, 1313-1324, doi:10.5194/cp-11-1313-2015, 2015
Parallelisms between sea surface temperature changes in the western tropical Atlantic (Guiana Basin) and high latitude climate signals over the last 140 000 years
Summary: The alkenone sea surface temperatures in the Guiana Basin show a rapid transmission of the climate variability from arctic to tropical latitudes during the last two interglacials (MIS1 and MIS5e) and warm long interstadials (MIS5d-a). In contrast, the abrupt variability of the glacial interval does follow the North Atlantic climate but is also shaped by precessional changes. This arctic to tropical decoupling occurs when the Atlantic meridional overturning circulation is substantially reduced.
Clim. Past, 11, 1297-1311, doi:10.5194/cp-11-1297-2015, 2015
Orbital control on late Miocene climate and the North African monsoon: insight from an ensemble of sub-precessional simulations
Summary: This paper investigates the climatic response to orbital forcing through the analysis of an ensemble of simulations covering a late Miocene precession cycle. Including orbital variability in our model–data comparison reduces the mismatch between the proxy record and model output. Our results indicate that ignoring orbital variability could lead to miscorrelations in proxy reconstructions. The North African summer monsoon's sensitivity is high to orbits, moderate to paleogeography and low to CO2.
Clim. Past, 11, 1271-1295, doi:10.5194/cp-11-1271-2015, 2015
Microfossil evidence for trophic changes during the Eocene–Oligocene transition in the South Atlantic (ODP Site 1263, Walvis Ridge)
Summary: Deep-sea sediments at ODP Site 1263 (Walvis Ridge, South Atlantic) show that marine calcifying algae decreased in abundance and size at the Eocene-Oligocene boundary, when the Earth transitioned from a greenhouse to a more glaciated and cooler climate. This decreased the food supply for benthic foraminifer communities. The plankton rapidly responded to fast-changing conditions, such as seasonal nutrient availability, or to threshold-levels in pCO2, cooling and ocean circulation.
Clim. Past, 11, 1249-1270, doi:10.5194/cp-11-1249-2015, 2015
Climatic variability and human impact during the last 2000 years in western Mesoamerica: evidence of late Classic (AD 600–900) and Little Ice Age drought events
Summary: We present results from western Mexico, where very few palaeoclimatic research sites exist. The record has good chronological resolution (ca. 20 years) and clear climatic trends during the last 2ka. The most important signals are: dry conditions during the late Classic (AD 500 to 1000), especially from AD 600 to 800, and low lake levels during the LIA, in two phases that follow Spörer and Maunder solar minima. Drier conditions are related with a lower intensity of the North American monsoon.
Clim. Past, 11, 1239-1248, doi:10.5194/cp-11-1239-2015, 2015
Mammal faunal change in the zone of the Paleogene hyperthermals ETM2 and H2
Summary: This project describes mammal faunal response in the zone of the ETM2 and H2 hyperthermals (rapid global warming events) of the early Paleogene in the south-central Bighorn Basin, WY. The response includes changes in faunal structure and species relative body size. Comparative analysis suggests that environmental moisture and rate of change are important moderators of response.
Clim. Past, 11, 1223-1237, doi:10.5194/cp-11-1223-2015, 2015
Early-Holocene warming in Beringia and its mediation by sea-level and vegetation changes
Summary: The ongoing warming of the Arctic is producing changes in vegetation and hydrology that, coupled with rising sea level, could mediate global changes. We explored this possibility using regional climate model simulations of a past interval of warming in Beringia and found that the regional-scale changes do strongly mediate the responses to global changes, amplifying them in some cases, damping them in others, and, overall, generating considerable spatial heterogeneity in climate change.
Clim. Past, 11, 1197-1222, doi:10.5194/cp-11-1197-2015, 2015
Astronomical calibration of the geological timescale: closing the middle Eocene gap
Summary: Testing hypotheses for mechanisms and dynamics of past climate change relies on the accuracy of geological dating. Development of a highly accurate geological timescale for the Cenozoic Era has previously been hampered by discrepancies between radioisotopic and astronomical dating methods, as well as a stratigraphic gap in the middle Eocene. We close this gap and provide a fundamental advance in establishing a reliable and highly accurate geological timescale for the last 66 million years.
Clim. Past, 11, 1181-1195, doi:10.5194/cp-11-1181-2015, 2015
Coupled Northern Hemisphere permafrost–ice-sheet evolution over the last glacial cycle
Summary: In this paper we explore the permafrost–ice-sheet interaction using the fully coupled climate–ice-sheet model CLIMBER-2 with the addition of a newly developed permafrost module. We find that permafrost has a moderate but significant effect on ice sheet dynamics during the last glacial cycle. In particular at the Last Glacial Maximum the inclusion of permafrost leads to a 15m sea level equivalent increase in Northern Hemisphere ice volume when permafrost is included.
Clim. Past, 11, 1165-1180, doi:10.5194/cp-11-1165-2015, 2015
A millennial summer temperature reconstruction for northeastern Canada using oxygen isotopes in subfossil trees
Summary: This paper presents a millennial δ18O series and the reconstruction of the maximal temperature. The maximal replication and annual resolution have been obtained by using cohort sampling method. Three contrasted climatic periods have been identified: the medieval warm period (~997-1250; the warmest), the little ice age (~1450-1880) and the modern period (1970-2000) that is one of the fastest warming over the last millennium.
Clim. Past, 11, 1153-1164, doi:10.5194/cp-11-1153-2015, 2015
Multi-century lake area changes in the Southern Altiplano: a tree-ring-based reconstruction
Summary: A 601-year lake area reconstruction in NW Argentina and SW Bolivia, characterized the occurrence of annual to multi-decadal lake area fluctuations and its main oscillation modes of variability. Our reconstruction points out that the late 20th century decrease in lake area was exceptional over the period 1407–2007. A persistent negative trend in lake area is clear in the reconstruction and consistent with glacier retreat and other climate proxies from the Altiplano and the tropical Andes.
Clim. Past, 11, 1139-1152, doi:10.5194/cp-11-1139-2015, 2015
On the occurrence of annual layers in Dome Fuji ice core early Holocene ice
Clim. Past, 11, 1127-1137, doi:10.5194/cp-11-1127-2015, 2015
Optimal ranking regime analysis of TreeFlow dendrohydrological reconstructions
Summary: A new approach to time series analysis - the ORR method - was used to evaluate reconstructed western US streamflow records during 1500-2007. This method shows an interesting pattern of alternating drought and wet periods during the late 16th and 17th centuries, a period with relatively few drought or wet periods during the 18th century, and the and the reappearance of alternating dry and wet periods during the 19th and early 20th centuries.
Clim. Past, 11, 1107-1125, doi:10.5194/cp-11-1107-2015, 2015
Comment on "Radiative forcings for 28 potential Archean greenhouse gases" by Byrne and Goldblatt (2014)
Summary: In the article Clim Past 10, 1779 (2014), the HITRAN2012 database was employed to evaluate the radiative forcing of 28 Archean gases. The authors claimed that for NO2, H2O2, C2H4, CH3OH, and CH3Br there are severe disagreements between cross sections generated from the HITRAN line-by-line data and those of the PNNL experimental database. In this work we show that the differences are not nearly at the scale suggested by the authors, and their conclusions about these gases and HO2 are not correct.
Clim. Past, 11, 1097-1105, doi:10.5194/cp-11-1097-2015, 2015
A regional climate palaeosimulation for Europe in the period 1500–1990 – Part 2: Shortcomings and strengths of models and reconstructions
Clim. Past, 11, 1077-1095, doi:10.5194/cp-11-1077-2015, 2015
Multiscale monsoon variability during the last two climatic cycles revealed by spectral signals in Chinese loess and speleothem records
Summary: Multiscale signals were decomposed from Chinese loess and speleothem records over the last 260 kyr. We found great glacial and orbital impacts on the loess grain size changes and dominant precession forcing in the speleothem δ18O variability. The millennial components are evident in the loess and speleothem proxies with variances of 13 and 17%. Close matches of millennial monsoon events between these two proxies indicate similar driving force linked to high-latitude Northern Hemisphere climate.
Clim. Past, 11, 1067-1075, doi:10.5194/cp-11-1067-2015, 2015
Endless cold: a seasonal reconstruction of temperature and precipitation in the Burgundian Low Countries during the 15th century based on documentary evidence
Summary: This paper applies the methods of historical climatology to present a climate reconstruction for the area of the Burgundian Low Countries during the 15th century. The results are based on documentary evidence. Approximately 3000 written records derived from about 100 different sources were examined and converted into seasonal seven-degree indices of temperature and precipitation.
Clim. Past, 11, 1049-1066, doi:10.5194/cp-11-1049-2015, 2015
A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 1816
Summary: A data set of instrumental pressure and temperature observations for the early instrumental period (before ca. 1850) is described. This is the result of a digitisation effort involving the period immediately after the eruption of Mount Tambora in 1815, combined with the collection of already available sub-daily time series. The highest data availability is therefore for the years 1815 to 1817. An analysis of pressure variability and of case studies in Europe is performed for that period.
Clim. Past, 11, 1027-1047, doi:10.5194/cp-11-1027-2015, 2015
The Paleocene–Eocene Thermal Maximum at DSDP Site 277, Campbell Plateau, southern Pacific Ocean
Summary: Re-examination of a Deep Sea Drilling Project sediment core (DSDP Site 277) from the western Campbell Plateau has identified the initial phase of the Paleocene-Eocene Thermal Maximum (PETM) within nannofossil chalk, the first record of the PETM in an oceanic setting in the southern Pacific Ocean (paleolatitude of ~65°S). Geochemical proxies indicate that intermediate and surface waters warmed by ~6° at the onset of the PETM prior to the full development of the negative δ13C excursion.
Clim. Past, 11, 1009-1025, doi:10.5194/cp-11-1009-2015, 2015
Scaling laws for perturbations in the ocean–atmosphere system following large CO2 emissions
Summary: In this paper we find scaling relationships for perturbations to atmosphere and ocean variables from large transient CO2 emissions. We use a carbon cycle box model to calculate peak perturbations to a variety of ocean and atmosphere variables resulting from idealized emission events. As these scaling relationships depend on the physical setup, they represent a compact way of characterizing how different climates respond to large transient perturbations.
Clim. Past, 11, 991-1007, doi:10.5194/cp-11-991-2015, 2015