A reconstruction of global hydroclimate and dynamical variables over the Common Era

Steiger, Nathan J.; Smerdon, Jason E.; Cook, Edward R.; Cook, Benjamin I.

doi:10.1038/sdata.2018.86

Cited by 171 publications

(270 citation statements)

References 83 publications

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“…The representation of pan‐CONUS droughts in the PHYDA is consistent with what is recorded in the NADA in terms of both spatial features and frequency of occurrence. This validation of the PHYDA with regard to pan‐CONUS droughts supports prior validation exercises that have found the PHYDA and NADA to have strong grid‐level correlations from 1500 ‐ 2000 CE (Steiger et al, ) and further supports our use of the PHYDA as a new product in the current study. Regarding the ocean forcing of pan‐CONUS droughts, our analysis of the PHYDA corroborates the key model‐based findings in Baek et al () based on the instrumental period, namely, that pan‐CONUS droughts exhibit a robust association with cold Pacific conditions but not with warm Atlantic conditions.…”

Section: Discussionsupporting

confidence: 88%

Oceanic Drivers of Widespread Summer Droughts in the United States Over the Common Era

Baek

Steiger

Smerdon

et al. 2019

Geophysical Research Letters

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We examine oceanic drivers of widespread droughts over the contiguous United States (herein pan‐CONUS droughts) during the Common Era in what is one of the first analyses of the new Paleo Hydrodynamics Data Assimilation (PHYDA) product. The canonical understanding of oceanic influences on North American hydroclimate suggests that pan‐CONUS droughts are forced by a contemporaneous cold tropical Pacific Ocean and a warm tropical Atlantic Ocean. We test this hypothesis using the paleoclimate record. Composite analyses find a robust association between pan‐CONUS drought events and cold tropical Pacific conditions, but not with warm Atlantic conditions. Similarly, a self‐organizing map analysis shows that pan‐CONUS drought years are most commonly associated with a global sea surface temperature pattern displaying strong La Niña and cold Atlantic Multidecadal Oscillation (AMO) conditions. Our results confirm previous model‐based findings for the instrumental period and show that cold tropical Pacific Ocean conditions are the principal driver of pan‐CONUS droughts on annual timescales.

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Section: Discussionsupporting

confidence: 88%

Oceanic Drivers of Widespread Summer Droughts in the United States Over the Common Era

Baek

Steiger

Smerdon

et al. 2019

Geophysical Research Letters

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“…Moreover, in our study, the calibration data set (i.e., GISTEMP) is independent from the verification data sets (i.e., HadCRUT4 and 20CR‐V2c). Therefore, the verification process is reasonable, because it is in line with the previous PDA‐based studies (Hakim et al, ; Perkins & Hakim, ; Steiger et al, ) and conforms to the independence rule between the calibration data and the verification data.…”

Section: Resultssupporting

confidence: 78%

An Artificial Neural Networks‐Based Tree Ring Width Proxy System Model for Paleoclimate Data Assimilation

Fang

2019

J Adv Model Earth Syst

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Constructing suitable tree ring width (TRW) proxy system models (PSMs) is an emerging research focus in paleoclimate data assimilation (PDA). Currently, however, it is unknown as to which TRW PSMs are optimal for practical PDA applications. This study proposes an artificial neural networks (ANN)‐based TRW PSM and compares its performance with those of existing TRW PSMs, including linear univariate model, linear multivariate model, and physically based VS‐Lite model. The results show that ANN‐based TRW PSM is more suitable for practical PDA applications than other three TRW PSMs in terms of performance and universality. Overall, the performances of the four TRW PSMs in PDA can be ranked as follows (from best to worst): ANN, linear multivariate model, linear univariate model, and physically based VS‐Lite model. In addition, the results of our study not only indicate that the ANN model is a really effective tool for constructing TRW PSM in practical PDA applications but also imply that the ANN model has the potential to provide new insights into the construction of other types of PSMs (e.g., speleothem δ18O PSM) when physics of the climate‐proxy relationships cannot be described fully in advance.

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“…Homogeneity can be an issue for long stations. For example, there is a hot bias for sunny days due to the lack of shielding of summer temperature measurements before the invention of the Stevenson screen in 1864 (Stevenson 1864, Böhm et al 2010, Naylor 2019 et al , Steiger et al 2018. Also, sea ice data from the early 20th century are being increasingly digitised, allowing better reflection, for example, of the early 20th century sea ice retreat in data (Titchner and Rayner 2014, Walsh et al 2017, Hegerl et al 2018.…”

Section: Methodsmentioning

confidence: 99%

Causes of climate change over the historical record

Hegerl

Brönnimann

Cowan

et al. 2019

Environ. Res. Lett.

128

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This review addresses the causes of observed climate variations across the industrial period, from 1750 to present. It focuses on long-term changes, both in response to external forcing and to climate variability in the ocean and atmosphere. A synthesis of results from attribution studies based on palaeoclimatic reconstructions covering the recent few centuries to the 20th century, and instrumental data shows how greenhouse gases began to cause warming since the beginning of industrialization, causing trends that are attributable to greenhouse gases by 1900 in proxy-based temperature reconstructions. Their influence increased over time, dominating recent trends. However, other forcings have caused substantial deviations from this emerging greenhouse warming trend: volcanic eruptions have caused strong cooling following a period of unusually heavy activity, such as in the early 19th century; or warming during periods of low activity, such as in the early-to-mid 20th century. Anthropogenic aerosol forcing most likely masked some global greenhouse warming over the 20th century, especially since the accelerated increase in sulphate aerosol emissions starting around 1950. Based on modelling and attribution studies, aerosol forcing has also influenced regional temperatures, caused long-term changes in monsoons and imprinted on Atlantic variability. Multi-decadal variations in atmospheric modes can also cause longterm climate variability, as apparent for the example of the North Atlantic Oscillation, and have influenced Atlantic ocean variability. Long-term precipitation changes are more difficult to attribute to external forcing due to spatial sparseness of data and noisiness of precipitation changes, but the observed pattern of precipitation response to warming from station data supports climate model simulated changes and with it, predictions. The long-term warming has also led to significant differences in daily variability as, for example, visible in long European station data. Extreme events over the historical record provide valuable samples of possible extreme events and their mechanisms.

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A reconstruction of global hydroclimate and dynamical variables over the Common Era

Cited by 171 publications

References 83 publications

Oceanic Drivers of Widespread Summer Droughts in the United States Over the Common Era

Oceanic Drivers of Widespread Summer Droughts in the United States Over the Common Era

An Artificial Neural Networks‐Based Tree Ring Width Proxy System Model for Paleoclimate Data Assimilation

Causes of climate change over the historical record

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