Climate proxies from marine sediments provide an important record of past temperatures, but contain noise from many sources. These include mixing by burrowing organisms, seasonal and habitat biases, measurement error, and small sample size effects. We have created a forward model that simulates the creation of proxy records and provides it as a user-friendly R package. It allows multiple sources of uncertainty to be considered together when interpreting proxy climate records.

The 4.2 ka event is generally characterized as an approximately 300-year period of major global climate anomaly. However, the climatic manifestation of this event remains unclear in the Indian monsoon domain. Our high-resolution and precisely dated speleothem record from Meghalaya, India, characterizes the event as consisting of a series of multi-decadal droughts between 3.9 and 4.0 ka rather than a singular pulse of multi-centennial drought as previously thought.

The 4.2 ka event between 4.2 and 3.9 ka has been widely discussed in the Northern Hemsiphere but less reported in the Southern Hemisphere. Here, we use speleothem records from Rodrigues in the southwestern Indian Ocean spanning from 6000 to 3000 years ago to investigate the regional hydro-climatic variability. Our records show no evidence for an unusual climate anomaly between 4.2 and 3.9 ka. Instead, it shows a multi-centennial drought between 3.9 and 3.5 ka.

The sediment deposited off the coast of Portugal includes the remains of marine organisms and pollen washed to sea from Iberia. Analysis of both the pollen and the ocean sediments has revealed that the type and density of vegetation on land changed in concert with shifts in ocean temperature over centuries to tens of millennia. Proxies for climate in Portuguese stalagmites from the last two glacial periods show precipitation was reduced when sea surface temperatures fell.

The paper presents a worldwide state of the art of droughts fluctuations based on documentary data. It gives an overview of achievements related to different kinds of documentary evidence with their examples and an overview of papers presenting long-term drought chronologies over the individual continents, analysis of the most outstanding drought events, the influence of external forcing and large-scale climate drivers, and human impacts and responses. It recommends future research directions.

We analyze the changes in oceanic carbon dynamics, using a state-of-the-art Earth system model, by comparing two quasi-equilibrium states: the early, warm Eemian (125 ka) versus the cooler, late Eemian (115 ka). Our results suggest a considerably weaker ocean dissolved inorganic carbon storage at 125 ka, an alteration of the deep-water geometry and ventilation in the South Atlantic, and heterogeneous changes in phosphate availability and carbon export between the Pacific and Atlantic basins.

Carbon’s radioactive isotope (radiocarbon) is a useful tool for oceanographers investigating carbon cycling in the modern ocean and ice age oceans (using foraminifera microfossils). Here we used sediment cores with excellent age constraints and abundant foraminifera microfossils to examine interspecies radiocarbon differences. All species demonstrate the same extreme radiocarbon depletion, and we argue that these observations represent important changes in seawater carbon chemistry.

We present our results from a radiocarbon-dated core collected in central Nares Strait, NW Greenland. Sedimentological and geochemical data reveal that marine sedimentation began ca. 9.0 cal ka BP with the complete opening of the strait occurring at 8.3 cal ka BP. The collapse of the glacial buttress in central Nares Strait led to accelerated glacial fluxes of the bordering ice sheets between 8.3 and 7.5 cal ka BP, while the Humboldt Glacier retreated in eastern Kane Basin ca. 8.1 cal ka BP.

Past cold ice age temperatures and the subsequent warming towards the Holocene had large consequences for soil organic carbon (SOC) stored in perennially frozen grounds. Using an Earth system model we show how the spread in areas affected by permafrost have changed under deglacial warming, along with changes in SOC accumulation. Our model simulations suggest phases of circum-Arctic permafrost SOC gain and losses, with a net increase in SOC between the last glacial maximum and the pre-industrial.

Proxy data on climate variations contain noise from many sources and, for reliable estimates, we need to determine those temporal scales at which the climate signal in the proxy record dominates the noise. We developed a method to derive timescale-dependent estimates of temperature proxy signal-to-noise ratios, which we apply and discuss in the context of Antarctic ice-core records but which in general are applicable to a large set of palaeoclimate records.

Multiple components of the global climate system record a transition ~ 430 ka from lower- to higher-amplitude glacial cycles. Statistical analyses of globally distributed climate proxies show that a sequence of events including persistent Asian summer monsoons, weak glaciation, and reorganization of water masses preceded the transition to higher interglacial values for temperature, atmospheric greenhouse gases, and sea level.