Pacific multidecadal (50–70 year) variability instigated by volcanic forcing during the Little Ice Age (1250–1850)

The Pacific decadal oscillation (PDO) is the leading mode of decadal climate variability over the North Pacific. However, it remains unknown to what extent external forcings can influence the PDO’s periodicity and magnitude over the past 2000 years. We show that the paleo-assimilation products (LMR) and proxy data suggest a 20–40 year PDO occurred during both the Mediaeval Climate Anomaly (MCA, ~ 750–1150) and Little Ice Age (LIA, ~ 1250–1850) while a salient 50–70 year variance peak emerged during the LIA. These results are reproduced well by the CESM simulations in the all-forcing (AF) and single volcanic forcing (Vol) experiments. We show that the 20–40 year PDO is an intrinsic mode caused by internal variability but the 50–70 year PDO during the LIA is a forced mode primarily shaped by volcanic forcing. The intrinsic mode develops in tandem with tropical ENSO-like anomalies, while the forced mode develops from the western Pacific and unrelated to tropical sea surface temperature anomalies. The volcanism-induced land–sea thermal contrast may trigger anomalous northerlies over the western North Pacific (WNP), leading to reduced northward heat transport and the cooling in the Kuroshio–Oyashio Extension (KOE), generating the forced mode. A 50–70 year Atlantic multidecadal oscillation founded during the LIA under volcanic forcing may also contribute to the forced mode. These findings shed light on the interplay between the internal variability and external forcing and the present and future changes of the PDO.

Incorporating decadal climate variability information in the operation and design of water infrastructure

The high thermal and mechanical inertia of the oceans results in slow changes in sea surface temperatures (SSTs). Changes in SSTs, in turn, can impact atmospheric circulation including water vapor transport, precipitation, and temperatures throughout the world. The Pacific Decadal Oscillation (PDO), the tropical Atlantic SST gradient variability, and the West Pacific Warm Pool are patterns of natural climate variability that tend to persist over decadal time periods. There are current efforts to produce decadal climate predictions, but there is limited understanding if this information can be used in water resources management. Understanding the current state of decadal climate variability (DCV) phenomena and the probability of persisting in that state may be useful information for water managers. This information could improve forecasts that aid operations and short-term planning for reservoir management, domestic and industrial water supplies, flood risk management, energy production, recreation, inland navigation, and irrigation. If conditions indicate a higher likelihood of drought, reservoir managers could reduce flood storage space and increase storage for conservation purposes. Improved forecasts for irrigation could result in greater efficiencies by shifting crops and rotational crop patterns. The potential benefits of using a forecast must be balanced against the risk of damages if the forecast is wrong. Seasonal forecasts using DCV information could also be used to inform drought triggers. If DCV indices indicate that the climate has a higher probability of dry conditions, drought contingency plans could be triggered earlier. Understanding of DCV phenomena could also improve long-range water resources planning. DCV can manifest itself in relatively short-term hydrologic records as linear trends that complicate hydrologic frequency analysis, which has traditionally assumed that hydrologic records are stationary.

Underlying drivers of decade-long fluctuation in the global mean sea-level rise

Natural climate variability can mask the background trend of global mean sea-level (GMSL) caused by global warming. Recent advances in satellite measurements and ocean heat-content estimates have enabled the monitoring of GMSL budget components and provide insights into ocean effects on the Earth’s energy imbalance and hydrology. We observed a decadal fluctuation in GMSL rise, which coincides with an increasing trend in the 2010s after the warming “hiatus” during the 2000s, and demonstrated that the rate of sea-level rise can be attributed to climate-related decadal fluctuations in ocean heat storage and hydrology. Since ~2011, the decadal climate variability has resulted in additional ocean mass gain (271±89 Gt yr-1) from glacier-free land water storage and increased ocean heat uptake (0.28±0.17 W m-2), increasing the GMSL rise rate by 1.4±0.4 mm yr-1. The suggested estimates of sea-level and Earth’s energy budgets highlight the importance of natural variability in understanding the impacts of the ongoing sea-level rise.

Unlocking weather observations from the Societas Meteorologica Palatina (1781–1792)

In recent years, instrumental observations have become increasingly important in climate research, allowing past daily-to-decadal climate variability and weather extremes to be explored in greater detail. The 18th century saw the formation of several short-lived meteorological networks of which the one organised by the Societas Meteorologica Palatina is arguably the most well known. This network stood out as one of the few that efficiently managed to control its members, integrating, refining, and publishing measurements taken from numerous stations around Europe and beyond. Although much has been written about the network in both history, science, and individual prominent series used for climatological studies, the actual measurements have not yet been digitised and published in extenso. This paper represents an important step towards filling this perceived gap in research. Here, we provide an inventory listing the availability of observed variables for the 37 stations that belonged to the society's network and discuss their historical context. Most of these observations have been digitised, and a considerable fraction has been converted and formatted. In this paper, we focus on the temperature and pressure measurements, which have been corrected and homogenised. We then demonstrate their potential for climate research by analysing two cases of extreme weather. The recovered series will have wide applications and could contribute to a better understanding of the mechanisms behind climatic variations and extremes as well as the societal reactions to adverse weather. Even the shorter series could be ingested into reanalyses and improve the quality of large-scale reconstructions.

El Niño Southern Oscillation and decadal climate variability impacts on crop yields and adaptation value.

Ocean-atmospheric phenomena (OAP) have been found to be associated with regional climate variability and, in turn, agricultural production. Previous research has shown that advance information on OAP and its climate implications could provide valuable opportunities to adjust agriculture practices. In this study, we review OAP effects on crop yields, covering both shorter-term El Niño Southern Oscillation (ENSO) and longer-term ocean-related decadal climate variability (DCV) phenomena, such as Pacific Decadal Oscillation (PDO), the Tropical Atlantic Gradient (TAG), and the West Pacific Warm Pool (WPWP). We review both statistical approaches and simulation models that have been used to assess OAP impacts on crop yields. Findings show heterogeneous impacts across crops, regions, OAP phases, and seasons. Evidence also indicates that more frequent and extreme OAP phases would damage agriculture. However, economic gains could be achieved via adaptation strategies responding to the early release of OAP phase information. Discussions on current knowledge gaps and future research issues are included.

El Niño southern oscillation and decadal climate variability impacts on crop yields and adaptation value.

Ocean-atmospheric phenomena (OAP) have been found to be associated with regional climate variability and, in turn, agricultural production. Previous research has shown that advance information on OAP and its climate implications could provide valuable opportunities to adjust agriculture practices. In this study, we review OAP effects on crop yields, covering both shorter-term El Niño Southern Oscillation (ENSO) and longer-term ocean-related decadal climate variability (DCV) phenomena, such as Pacific Decadal Oscillation (PDO), the Tropical Atlantic Gradient (TAG), and the West Pacific Warm Pool (WPWP). We review both statistical approaches and simulation models that have been used to assess OAP impacts on crop yields. Findings show heterogeneous impacts across crops, regions, OAP phases, and seasons. Evidence also indicates that more frequent and extreme OAP phases would damage agriculture. However, economic gains could be achieved via adaptation strategies responding to the early release of OAP phase information. Discussions on current knowledge gaps and future research issues are included.