The worst North American drought year of the last millennium: 1934

Cook, Benjamin I.; Seager, Richard; Smerdon, Jason E.

doi:10.1002/2014gl061661

Cited by 79 publications

(83 citation statements)

References 47 publications

(78 reference statements)

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“…Recent work suggests that record warmth could have made the current event the most severe annual-scale drought of the past millennium (12). However, numerous paleoclimate records also suggest that the region has experienced multidecadal periods in which most years were in a drought state (14,39,41,42), albeit less acute than the current California event (12,39,41). Although multidecadal ocean variability was a primary cause of the megadroughts of the last millenium (41), the emergence of a condition in which there is ∼100% probability of an extremely warm year (Fig.…”

Section: Resultsmentioning

confidence: 99%

Anthropogenic warming has increased drought risk in California

Diffenbaugh

Swain²,

Touma³

2015

Proc. Natl. Acad. Sci. U.S.A.

1,125

872

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California is currently in the midst of a record-setting drought. The drought began in 2012 and now includes the lowest calendar-year and 12-mo precipitation, the highest annual temperature, and the most extreme drought indicators on record. The extremely warm and dry conditions have led to acute water shortages, groundwater overdraft, critically low streamflow, and enhanced wildfire risk. Analyzing historical climate observations from California, we find that precipitation deficits in California were more than twice as likely to yield drought years if they occurred when conditions were warm. We find that although there has not been a substantial change in the probability of either negative or moderately negative precipitation anomalies in recent decades, the occurrence of drought years has been greater in the past two decades than in the preceding century. In addition, the probability that precipitation deficits co-occur with warm conditions and the probability that precipitation deficits produce drought have both increased. Climate model experiments with and without anthropogenic forcings reveal that human activities have increased the probability that dry precipitation years are also warm. Further, a large ensemble of climate model realizations reveals that additional global warming over the next few decades is very likely to create ∼100% probability that any annual-scale dry period is also extremely warm. We therefore conclude that anthropogenic warming is increasing the probability of co-occurring warm-dry conditions like those that have created the acute human and ecosystem impacts associated with the "exceptional" 2012-2014 drought in California.drought | climate extremes | climate change detection | event attribution | CMIP5

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Section: Resultsmentioning

confidence: 99%

Anthropogenic warming has increased drought risk in California

Diffenbaugh

Swain²,

Touma³

2015

Proc. Natl. Acad. Sci. U.S.A.

1,125

872

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“…Other two, more recent catastrophic US droughts were in 1956, estimated from PDSI, and 1988, estimated from both PDSI and VHI (Kogan 2001;Hayes et al 2012;Cook et al 2014aCook et al , 2014b. These catastrophic droughts were compared with the strongest drought of 2012 (table 2).…”

Section: Drought In Historical Perspectivementioning

confidence: 99%

“…Following these considerations, a non-drought year is classified if the stress-affected area in the MM, S and S category is less than 40%, 10% and 5%, respectively, of the entire region. Similar criterion was selected for classifying extreme drought from Palmer Drought Severity Index (PDSI) (Cook et al 2014a(Cook et al , 2014b. In addition to the entire western two-thirds of the USA, analysis was performed for each state.…”

Section: Drought Area and Intensitiesmentioning

confidence: 99%

“…The past 100-year US droughts have been evaluated using the PDSI (which assesses a balance between JuneÀAugust moisture supply (rainfall) and water demand (modelled evapotranspiration)). Following the PDSI, the DB drought of the 1930s continued for seven years (1932À1939) and occupied 71.6% of the western USA in 1934 (Wilhite 2000;Hayes et al 2012;Cook et al 2014aCook et al , 2014b.…”

Section: Drought In Historical Perspectivementioning

confidence: 99%

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2006–2015 mega-drought in the western USA and its monitoring from space data

Kogan

Guo²

2015

Geomatics, Natural Hazards and Risk

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“…the most severe droughts since the Dust Bowl era of the 1930s (17,18). The drought caused substantial economic damage, particularly for agricultural production (SI Appendix).…”

mentioning

confidence: 99%

Warm spring reduced carbon cycle impact of the 2012 US summer drought

Wolf

Keenan

Fisher

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

371

325

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The global terrestrial carbon sink offsets one-third of the world's fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally warm temperatures and the most severe drought since the Dust Bowl era of the 1930s, resulting in substantial economic damage. It is crucial to understand the dynamics of such events because warmer temperatures and a higher prevalence of drought are projected in a changing climate. Here, we combine an extensive network of direct ecosystem flux measurements with satellite remote sensing and atmospheric inverse modeling to quantify the impact of the warmer spring and summer drought on biosphereatmosphere carbon and water exchange in 2012. We consistently find that earlier vegetation activity increased spring carbon uptake and compensated for the reduced uptake during the summer drought, which mitigated the impact on net annual carbon uptake. The early phenological development in the Eastern Temperate Forests played a major role for the continental-scale carbon balance in 2012. The warm spring also depleted soil water resources earlier, and thus exacerbated water limitations during summer. Our results show that the detrimental effects of severe summer drought on ecosystem carbon storage can be mitigated by warming-induced increases in spring carbon uptake. However, the results also suggest that the positive carbon cycle effect of warm spring enhances water limitations and can increase summer heating through biosphere-atmosphere feedbacks.seasonal climate anomalies | carbon uptake | ecosystem fluxes | biosphere-atmosphere feedbacks | eddy covariance A n increase in the intensity and duration of drought (1, 2), along with warmer temperatures, is projected for the 21st century (3). Warmer and drier summers can substantially reduce photosynthetic activity and net carbon uptake (4). In contrast, warmer temperatures during spring and autumn prolong the period of vegetation activity and increase net carbon uptake in temperate ecosystems (5), sometimes even during spring drought (6). Atmospheric CO 2 concentrations suggest that warm-springinduced increases in carbon uptake could be cancelled out by the effects of warmer and drier summers (7). However, the extent and variability of potential compensation on net annual uptake using direct observations of ecosystem carbon exchange have not yet been examined for specific climate anomalies.In addition to perturbations of the carbon cycle, warmer spring temperatures can have an impact on the water cycle by increasing evaporation from the soil and plant transpiration (8-10), which reduces soil moisture. Satellite observations suggest that warmer spring and longer nonfrozen periods enhance summer drying via hydrological shifts in soil moisture status (11). Climate model simulations also indicate a soil moisture-temperature feedback between early vegetation green-up in spring and extreme temperatures in summer (12, 13). Soil water deficits during drou...

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The worst North American drought year of the last millennium: 1934

Cited by 79 publications

References 47 publications

Anthropogenic warming has increased drought risk in California

Anthropogenic warming has increased drought risk in California

2006–2015 mega-drought in the western USA and its monitoring from space data

Warm spring reduced carbon cycle impact of the 2012 US summer drought

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