The stratospheric ozone layer plays a key role in atmospheric thermal structure and circulation. Here, with a chemistry–climate model, we evaluate the potential role of stratospheric ozone chemistry in the case of Eocene hot conditions. Our results suggest that using stratospheric ozone calculated by the modeled Eocene conditions instead of the commonly specified preindustrial ozone distribution could change the simulated global surface air temperature by as much as 14 %.

The paper analyses a weather diary of the Reverend Šimon Hausner from Buchlovice in south-east Moravia, Czech Republic, in the 1803–1831 period. From daily weather records, series of numbers of precipitation days, cloudiness, strong winds, fogs, and thunderstorms were created. These records were further used to interpret weighted temperature and precipitation indices. Records of Šimon Hausner represent an important contribution to the study of climate fluctuations on the central European scale.

The mid-Holocene has been an excellent target for comparing models and data. This work shows that, over China, all the ocean–atmosphere general circulation models involved in PMIP3 show a very large discrepancy with pollen data reconstruction when comparing annual and seasonal temperature. It demonstrates that to reconcile models and data and to capture the signature of seasonal thermal response, it is necessary to integrate non-linear processes, particularly those related to vegetation changes.

An updated Last Millennium Reanalysis is presented, using an expanded multi-proxy database, and proxy models representing the seasonal characteristics of proxy records, in addition to the dual sensitivity to temperature and moisture of tree-ring-width chronologies. We show enhanced skill in spatial reconstructions of key climate variables in the updated reanalysis, compared to an earlier version, resulting from the combined influences of the enhanced proxy network and improved proxy modeling.

A new method for probabilistic spatial reconstructions of past climate states is presented, which combines pollen data with a multi-model ensemble of climate simulations in a Bayesian framework. The approach is applied to reconstruct summer and winter temperature in Europe during the mid-Holocene. Our reconstructions account for multiple sources of uncertainty and are well suited for quantitative statistical analyses of the climate under different forcing conditions.

The historical climatology has remarkable research potentialities. However, historical climatology has some methodological limitations. This study presents a new methodology (COST) that allows us to perform climate reconstructions with monthly resolution. The variability of the climatic series obtained are coherent with previous studies. The new proposed method is objective and is not affected by social changes, which allows us to perform studies in regions with different languages and cultures.

In this multi-proxy study we present and critically discuss the hypothesis that during the early Aptian, platform-top hypoxia temporarily established in some of the vast epeiric seas of the central Tethys and triggered significant changes in reefal ecosystems. Data shown here shed light on the driving mechanisms that control poorly understood faunal patterns during OAE 1a in the neritic realm and provide evidence on the intricate relation between basinal and platform-top water masses.

The 18th and early 19th centuries saw pronounced climatic variations with impacts on the environment and society. Although instrumental meteorological data for that period exist, only a small fraction has been the subject of research. This study provides an overview of early instrumental meteorological records in Switzerland resulting from an archive survey and demonstrates the great potential of such data. It is accompanied by the online publication of the imaged data series and metadata.

Salgada Lagoon is a hypersaline lake investigated for its sedimentation history in order to interpret past climatic events. We studied the geochemistry of sediments from 5800 years ago until the present and found sea level oscillations, different climatic conditions, and proxies for vegetation cover and productivity, which highlight a dry event 4200 years ago that matches a global event of the same age, marking changes to favorable conditions for carbonates microbial mats and stromatolites.

A relation between mid-Holocene (MH) and future Arctic warming mechanisms is investigated with emphasis on the similarities and differences of physical processes. Simulations from 10 atmosphere–ocean general circulation models are analyzed. The several key processes are identified which are linked to multi-model mean response and multi-model variation of the response. This study suggests that knowledge of the MH Arctic climate has a potential to constrain future Arctic climate projections.

During the 19th century flood frequency was high in central Europe, but it was low in the mid-20th century. This paper tracks these decadal changes in flood frequency for the case of Switzerland from peak discharge data back to precipitation data and daily weather reconstructions. We find an increased frequency in flood-prone weather types during large parts of the 19th century and decreased frequency in the mid-20th century. Sea-surface temperature anomalies can only explain a small part of it.

The linearity of the climate response is strong on orbital and millennial scales throughout the Holocene but poor on the centennial and decadal scale. The regions of strong linear response on the millennial scale are mostly consistent with the orbital scale, notably western Eurasian, North Africa, the subtropical North Pacific, the tropical Atlantic and the Indian Ocean. This finding can improve our understanding of the regional climate response to various climate forcings.

In recent years, the data assimilation approach was adapted to the field of paleoclimatology to reconstruct past climate fields by combining model simulations and observations. To improve the performance of our paleodata assimilation system, we tested various techniques that are well established in weather forecasting and evaluated their impact on assimilating instrumental data and proxy records (tree rings).

To reconstruct past winter climate, we studied ice wedges at two sites in the Yana Highlands, interior Yakutia (Russia), the most continental region of the Northern Hemisphere. Our ice wedges of the upper ice complex unit of the Batagay megaslump and a river terrace show much more depleted stable-isotope compositions than other study sites in coastal and central Yakutia, reflecting lower winter temperatures and a higher continentality of the study region during Marine Isotope Stages 3 and 1.

The amount of O₂ in the atmosphere may have varied from as little as 10 % to as much as 35 % during the last 541 Myr. These changes are large enough to have led to changes in atmospheric mass, which may alter the radiative budget of the atmosphere. We present the first fully 3-D numerical model simulations to investigate the climate impacts of changes in O₂ during different climate states. We identify a complex new mechanism causing increases in surface temperature when O₂ levels were higher.

In this paper we present the longest grape harvest date (GHD) record reconstructed to date, i.e. Beaune (France, Burgundy) 1354–2018. Drawing on unedited archive material, the series is validated using the long Paris temperature series that goes back to 1658 and was used to assess April-to-July temperatures from 1354 to 2018. The distribution of extremely early GHD is uneven over the 664-year-long period of the series and mirrors the rapid global warming from 1988 to 2018.

The high-quality pollen records (collected from lakes and peat bogs) of the last 40 ka cal BP form north Asia are homogenized and the plant abundance signals are calibrated by the modern relative pollen productivity estimates. Calibrated plant abundances for each site are generally consistent with in situ modern vegetation, and vegetation changes within the regions are characterized by minor changes in the abundance of major taxa rather than by invasions of new taxa during the last 40 ka cal BP.

An ice core from Taylor Glacier, Antarctica, spans a period ~ 70 000 years ago when Earth entered the last ice age. Chemical analyses of the ice and air bubbles allow for an independent determination of the ages of the ice and gas bubbles. The difference between the age of the ice and the bubbles at any given depth, called ∆age, is unusually high in the Taylor Glacier core compared to the Taylor Dome ice core situated to the south. This implies a dramatic accumulation gradient between the sites.

We use an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled climate model to provide a protocol for using speleothem isotopic data for model evaluation, including screening the observations and the optimum period for the modern observational baseline. We also illustrate techniques through which the absolute isotopic values during any time period could be used for model evaluation.

We present a geochemical and petrographic study of the Kimmeridge Clay Formation from the Cleveland Basin (Yorkshire, UK). Our results indicate that deposition during this interval was very dynamic and oscillated between three distinct modes of sedimentation. In line with recent modelling results, we propose that these highly dynamic conditions were driven by changes in climate, which affected continental weathering, enhanced primary productivity, and led to organic carbon enrichment.

The Late Pliocene, 3.65–2.75 million years ago, is the most recent period in Earth's history that was warmer than the present. This makes it interesting for climatological research, because it provides a possible analogue for the near future. We used a coupled ice-sheet–climate model to simulate the behaviour of these systems during this period. We show that the warmest moment saw a sea-level rise of 8–14 m, with a CO₂ concentration of 320–400 ppmv.

Abrupt climate shifts of large magnitudes were common during glacial states, with explanations centred on the oceans. However, winds drive ocean surface currents so shifts in mean wind conditions could also have played a critical role. In a small ensemble of transient deglacial simulations, we find abrupt shifts in both jet stream location and variability over the North Atlantic. We show that the eastern North American ice sheet margin strongly constrains regional jet characteristics.