Recent  

Palaeoclimatological reconstructions aid our understanding of current and future climate change. In the Pliensbachian (Early Jurassic) a climatic cooling event occurred globally. We show that this cooling event has a significant impact on the depositional environment of the Cardigan Bay Basin, but that the 405 kyr eccentricity cycle remained the dominant control on terrestrial and marine depositional processes.

A gap in understanding climate variation exists at centennial-to-millennial scales, particularly for warm climates. Such variations challenge detection. They exceed direct observation but are geologically short. Centennial-to-millennial variations that may have influenced North America were examined over the past 7000 yr. Significant patterns were detected from fossil pollen and sedimentary lake-level changes, indicating ecological, hydrological, and likely human significance.

The reconstruction of paleoenvironments has long been a subject of great interest, particularly to study the past biodiversity. Paleoenvironmental proxies often show inconsistencies and age estimations can vary depending on the method used. We show the potential of paleoclimate simulations to address those discrepancies, illustrating the strong potential of our cross-disciplinary consistency approach to refine the context of archaeo/paleontological sites.

Based on the coupled model simulations with realistic early to middle Miocene paleogeography, we reveal that the enhanced South Asian summer monsoon in Middle Miocene is mainly caused by the uplift of Iranian Plateau (IP), rather than the Himalayas. The elevated IP insulates the warm and moist airs in the south of the IP and produces a low-level cyclonic circulation, which leads to the convergence of the warm and moist air in the northwestern India and enhancing the monsoonal precipitation.

Prior to 2.5 billion years ago, ozone was present in our atmosphere only in trace amounts. To understand how climate has changed in response to ozone build-up, we have run 3-D climate simulations with different amounts of ozone. We find that Earth's surface is about 3 to 4 degrees cooler with low ozone. This is caused by cooling of the upper atmosphere, where ozone is a warming agent. Its removal causes the upper atmosphere to become drier, weakening the greenhouse warming by water vapor.

The precise geometry of Atlantic circulation changes that accompanied rapid climate changes of the last glacial period is still unknown. Here we combine carbon isotopic records from 18 Atlantic sediment cores with numerical simulations performed by the Norwegian Earth System Model, in order to interpret the observed isotopic changes across a cold to warm transition. Our results show that the replacement of southern-sourced by northern-sourced water plays a dominant role below ~3000 m depth.

Ice core records are useful tools for reconstructing past climate. However, ice cores favour recording climate conditions at times when snowfall occurs. Large snowfall events in Antarctica are often associated with warmer-than-usual temperatures. We show that this results in a tendency for the Mount Brown South ice core record to preserve a temperature record with a warm bias.

Our ice core measurements show that methane, ethane and propane concentrations are significantly elevated above their past atmospheric background for Greenland ice samples containing mineral dust. The underlying co-production process happens during the classical discrete wet extraction of air from the ice sample and affects previous reconstructions of the inter-hemispheric difference of methane as well as methane stable isotope records derived from dusty Greenland ice.

We present an age scale for a new ice core drilled at Skytrain Ice Rise, an ice rise facing the Ronne Ice Shelf in Antarctica. Various measurements in the ice and air phases are used to match the ice core to other Antarctic cores that have already been dated. The 651 m ice core includes ice that is confidently dated to the last interglacial, 126,000 years ago. Older ice is found deeper down, but there are flow disturbances in the deeper ice.

Oxygen isotopes are used to date marine sediments via their similar large-scale ocean patterns over glacial cycles. However, the Arctic Ocean exhibits a different isotope pattern, creating uncertainty in the timing of past Arctic climate change. We find that the Arctic Ocean experienced large local oxygen isotope changes over glacial cycles. We attribute this to a breakdown of stratification during ice ages that allowed for a unique low isotope value to characterize the Arctic Ocean.

The Last Deglaciation is a period of large warming from 21,000 to 9,000 years ago, concomitant with ice sheet melting. Here we evaluate the impact of different ice sheet reconstructions and different processes linked to their changes. Changes of bathymetry and coastlines, although not often accounted for, cannot be neglected. Ice sheet melt results in fresh water into the ocean with large effects on ocean circulation, but the timing cannot explain the observed abrupt climate changes.

Climate reconstructions give insights into monthly and seasonal climate variability of the past few hundred years. However, for understanding past extreme weather events and for relating them to impacts, for example to periods of extreme floods, reconstructions on a daily time scale are needed. Here, we present a reconstruction of 250 years of high-resolution daily temperature and precipitation fields for Switzerland covering the period 1763 to 2020, which is based on instrumental measurements.

We reconstruct, for the first time, high-resolution temperatures prior to the Millennium eruption (946 AD) using a unique tree-ring proxy dataset in Changbai Mt., and compare them with modern temperatures. The temperatures during the last one and half centuries have stronger fluctuations, more frequent abruptions, and a weaker periodicity of temperature variance compared to the pre-Millennium temperatures. These recent changes correspond to long-term anthropogenic influences on regional climate.

This article provides a first look into the impact of drought in two cities in the eastern Netherlands from 1500 to 1795 on the basis of municipal records. It concludes that the impact of drought was sometimes similar but also different for both cities when focusing on specific aspects, such as water shortage and navigation. This strengthens the view that the impact of droughts could differ highly on a local level, which necessitates more emphasis on regional and local drought reconstructions.

Year-to-year variations in the weather conditions over the Indian Ocean have important consequences for the substantial fraction of the Earth's population that live near it. This work looks at how these variations respond to climate change - both past and future. The models rarely agree, suggesting a weak, uncertain response to climate change.

Tree-rings and ice cores provide information about the influence of past volcanic eruptions and changes in sun's activity on climate. However, this information is often incomplete and uncertain. We model different possible scenarios of past climate, and compare to information from natural archives. We confirm that sun's influence has been low, that uncertainty in the volcanic record can strongly influence simulated temperature variability.

We have modelled atmospheric methane continuously from the last glacial maximum to the present, using a state-of-the-art Earth System Model. Our model results compare well with reconstructions from ice cores and improve our understanding of a very intriguing period of Earth System history, the deglaciation, when atmospheric methane changed quickly and strongly.

One of the most common ways of reconstructing temperatures in the geologic past is by analyzing oxygen isotope ratios in fossil shells. However, converting these data to temperatures can be a technically complicated task. Here, we present a new online tool that automates this task. We show that some traditional methods for estimating seawater oxygen isotopes can produce large (>5 °C) errors in temperature estimates compared to newer methods which account for climate and regional variability.

Marine geologic data from NE Greenland provides new information about the behavior of the Greenland Ice Sheet during the last glacial period. Seafloor landforms suggest that a large, fast flowing ice stream moved south through Dove Bugt. Southern Dove Bugt was deglaciated from 11.2 ka BP, and evidence suggests that during a warmer than present period in the first part of the present interglacial (Holocene), grounded ice in the region had reached to or beyond its present-day position.

The Middle Eocene Climatic Optimum (MECO) is a global warming event that took place 40 Ma ago and lasted ca. 500 ky, inducing physical, chemical, and biotic changes on the Earth. In this work, we use stable isotopes to identify the MECO in Eocene deltaic deposits of S. Pyrenees. Our findings reveal enhanced deltaic progradation during the MECO, pointing at the important impact of global warming on fluvial sediment transport with implications for the consequences of current climate change.

A look at the climate evolution during the last warm period may allow to test ground for future climate conditions. We quantified the temperature evolution during the last interglacial using tiny amount of water trapped in the crystals of precisely dated stalagmites in caves from the southeastern European Alps. Our record indicates temperatures up to 2 °C warmer than today and an unstable climate during the first half of the Last Interglacial.

Stalagmites formed in caves provide valuable information about past changes in climate and vegetation conditions. In this contribution, we present a new method to better estimate past changes in the soil and vegetation productivity using the carbon isotopes and trace elements measured in stalagmites. Applying this method to other stalagmites should provide a better indication of past vegetation feedbacks to climate change.

We present in this manuscript the earliest records made at San Fernando, very close to Cádiz (SW Spain). Several previous works have already recovered a significant amount of meteorological records of interest in these localities. However, unnoticed previously more than 40,000 daily meteorological observations recorded at the Royal Observatory of the Spanish Navy (located in San Fernando) remained neither digitized nor studied. We analyze in detail these newly recovered meteorological readings.

This study uses diatom assemblages, biogenic silica and Si/Al data over the last 140 k yrs from core TAN1302-44 (64°54 S, 144°32 E), East Antarctica, to define glacial to interglacial paleoenvironments with respect to sea ice and ocean circulation. It found sea ice increased gradually during late glacial and retreated rapidly at the end of the last glacial. Minor influence of increased Circumpolar Deep Water influx occurred during last glaciation and last two deglacials.

Neogene climate cooling is thought to be accompanied by increased equator-to-pole temperature gradients, but mid-latitudes are poorly represented. We use biomarkers to reconstruct a 23 Myr continuous sea (sub)surface temperature record of the mid latitude Southern Ocean. We note a profound mid latitude cooling which narrowed the latitudinal temperature gradient with northward expansion of subpolar conditions. We surmise that this reflects the strengthening of the ACC and expansion of sea ice.

Four different phase relations are documented in past reconstructions, observation-based records and future projections of North Atlantic, Norwegian and Iceland Seas sea surface temperature relations. While in-phase is the expectation and the norm, out of phase relations occur in low and intermediate emission scenarios and in past warm climate states in equilibrium with a CO₂ level comparable to the future scenarios. The out of phase relations may result from changes in buoyancy forcing.