We reconstruct, for the first time, high-resolution temperatures prior to the Millennium Eruption (946 CE) using a unique tree-ring proxy dataset in Changbai Mountain and compare them with modern temperatures. The temperatures during the last 1.5 centuries have stronger fluctuations, more frequent abruption, 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.

We reconstructed sea ice and organic carbon composition variabilities based on biomarkers and carbon stable isotopes in the northern Chukchi Sea, western Arctic Ocean, over the past 200 years. Under permanent ice cover, organic carbon was dominated by land sources transported by sea ice and ocean currents, while local primary productivity was suppressed by light limitation. Since ice retreated in 20th century, organic carbon from primary production gradually overtook the terrestrial component.

Marine geologic data from NE Greenland provide new information about the behavior of the Greenland Ice Sheet from the last glacial period to present. Seafloor landforms suggest that a large, fast-flowing ice stream moved south through southern Dove Bugt. This region is believed to have been deglaciated from at least 11.4 ka cal BP. Ice in an adjacent fjord, Bessel Fjord, may have retreated to its modern position by 7.1 ka cal BP, and the ice halted or readvanced multiple times upon deglaciation.

Weather reconstructions could help us to better understand the mechanisms leading to, and the impacts caused by, climatic changes. This requires daily weather information such as diaries. Here I present the weather diary by Georg Christoph Eimmart from Nuremberg covering the period 1695–1704. This was a particularly cold period in Europe, and the diary helps to better characterize this climatic anomaly.

Regional warming will differ from global warming, and climate models perform poorly in the Southern Ocean. We reconstruct sea surface temperatures in the south-west Pacific during the mid-Pliocene, a time 3 million years ago that represents the long-term outcomes of 3 °C warming, which is expected for the future. Comparing these results to climate model simulations, we show that the south-west Pacific region will warm by 1 °C above the global average if atmospheric CO₂ remains above 350 ppm.

We used geochemical signals in shells preserved in sediments to create a 1750-year record of hydrological change in the Coorong Lagoon of South Australia. The record is interpreted to reflect the balance of evaporation and precipitation and shows that it has always been a highly evaporated system. The record also shows similarities to other environmental reconstructions from the region. This knowledge can increase our understanding of the potential impacts of environmental change.

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

Lake Petén Itzá, northern Guatemala, is one of the oldest lakes in the northern Neotropics. In this study, we analyzed geochemical and mineralogical data to decipher the hydrological response of the lake to climate and environmental changes between 59 and 15 cal ka BP. We also compare the response of Petén Itzá with other regional records to discern the possible climate forcings that influenced them. Short-term climate oscillations such as Greenland interstadials and stadials are also detected.

We present the weather diaries of the Kirch family from 1677–1774 containing weather observations made in Leipzig and Guben and, from 1701 onward, instrumental observations made in Berlin. We publish the imaged diaries (10 445 images) and the digitized measurements (from 1720 onward). This is one of the oldest and longest meteorological records from Germany. The digitized pressure data show good agreement with neighbouring stations, highlighting their potential for weather reconstruction.

Climate cycles with millennial periodicities are enigmatic because no Earth external climate forcing exists that operates on millennial timescales. Using a statistical analysis of a famous Greenlandic air temperature record, we show that two disparate energy sources (one astronomical and one centennial) fuel millennial climate variability. We speculate that two distinct Earth internal cryospheric/climatic/oceanic processes are responsible for the transfer of energy to millennial climate cycles.

CO₂ consumption by chemical alteration of continental silicate rocks regulates atmospheric CO₂ and Earth's mean climate. The efficiency of this regulation is affected by the amount of continental precipitation and may have been reduced 3 to 4 million years ago because of different patterns of sea surface temperature. This process could have contributed to the warmer climate of that time.

A mismatch between model- and proxy-based Holocene climate change may partially originate from the poor spatial coverage of climate reconstructions. Here we investigate quantitative reconstructions of mean annual temperature and annual precipitation from 1908 pollen records in the Northern Hemisphere. Trends show strong latitudinal patterns and differ between (sub-)continents. Our work contributes to a better understanding of the global mean.

The impact of land use and land cover change (LULCC) on the climate around 2500 years ago is studied using reconstructions and models. The results suggest that LULCC impacted the climate in parts of Europe. Reconstructed LULCC shows up to 1.5 °C higher temperature in parts of Europe in some seasons. This relatively strong response implies that anthropogenic LULCC that had occurred by the late prehistoric period may have already affected the European climate by 2500 years ago.

We compare past tree cover changes in Europe during the last 8000 years simulated with two dynamic global vegetation models and inferred from pollen data. The major model–data mismatch is related to the much earlier onset of anthropogenic deforestation in the data compared to the prescribed land use in the models. We show that land use, and not climate, is the main driver of the Holocene forest decline. The model–data agreement depends on the model tuning, challenging model–data comparisons.

Understanding the changes in atmospheric CO₂ during the last glacial cycle is crucial to comprehend the impact of climate change in the future. Previous research has hypothesised a key role of greater aeolian iron input into the Southern Ocean in influencing the global atmospheric CO₂ levels by impacting the changes in the marine phytoplankton response. In our study, we test this iron hypothesis using climate modelling and constrain the impact of ocean iron supply on global CO₂ decrease.