Influence of internal variability on population exposure to hydroclimatic changes

Justin S. Mankin, Daniel Viviroli, Mesfin Mekonnen, Arjen Ysbert Hoekstra, Radley M. Horton, Jason E. Smerdon, Noah S. Diggenbaugh

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Abstract

Future freshwater supply, human water demand, and people's exposure to water stress are subject to multiple sources of uncertainty, including unknown future pathways of fossil fuel and water consumption, and 'irreducible' uncertainty arising from internal climate system variability. Such internal variability can conceal forced hydroclimatic changes on multi-decadal timescales and near-continental spatial-scales. Using three projections of population growth, a large ensemble from a single Earth system model, and assuming stationary per capita water consumption, we quantify the likelihoods of future population exposure to increased hydroclimatic deficits, which we define as the average duration and magnitude by which evapotranspiration exceeds precipitation in a basin. We calculate that by 2060, backsim31%–35% of the global population will be exposed to >50% probability of hydroclimatic deficit increases that exceed existing hydrological storage, with up to 9% of people exposed to >90% probability. However, internal variability, which is an irreducible uncertainty in climate model predictions that is under-sampled in water resource projections, creates substantial uncertainty in predicted exposure: backsim86%–91% of people will reside where irreducible uncertainty spans the potential for both increases and decreases in sub-annual water deficits. In one population scenario, changes in exposure to large hydroclimate deficits vary from −3% to +6% of global population, a range arising entirely from internal variability. The uncertainty in risk arising from irreducible uncertainty in the precise pattern of hydroclimatic change, which is typically conflated with other uncertainties in projections, is critical for climate risk management that seeks to optimize adaptations that are robust to the full set of potential real-world outcomes.
Original languageEnglish
Article number044007
Pages (from-to)-
JournalEnvironmental research letters
Volume12
Issue number4
DOIs
Publication statusPublished - 2017

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Uncertainty
Population
Climate
fuel consumption
climate
Water
water demand
water stress
Drinking
fossil fuel
evapotranspiration
population growth
climate modeling
water resource
Fossil Fuels
timescale
Water Resources
Climate models
Evapotranspiration
exposure

Keywords

  • METIS-322158

Cite this

Mankin, J. S., Viviroli, D., Mekonnen, M., Hoekstra, A. Y., Horton, R. M., Smerdon, J. E., & Diggenbaugh, N. S. (2017). Influence of internal variability on population exposure to hydroclimatic changes. Environmental research letters, 12(4), -. [044007]. https://doi.org/10.1088/1748-9326/aa5efc
Mankin, Justin S. ; Viviroli, Daniel ; Mekonnen, Mesfin ; Hoekstra, Arjen Ysbert ; Horton, Radley M. ; Smerdon, Jason E. ; Diggenbaugh, Noah S. / Influence of internal variability on population exposure to hydroclimatic changes. In: Environmental research letters. 2017 ; Vol. 12, No. 4. pp. -.
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abstract = "Future freshwater supply, human water demand, and people's exposure to water stress are subject to multiple sources of uncertainty, including unknown future pathways of fossil fuel and water consumption, and 'irreducible' uncertainty arising from internal climate system variability. Such internal variability can conceal forced hydroclimatic changes on multi-decadal timescales and near-continental spatial-scales. Using three projections of population growth, a large ensemble from a single Earth system model, and assuming stationary per capita water consumption, we quantify the likelihoods of future population exposure to increased hydroclimatic deficits, which we define as the average duration and magnitude by which evapotranspiration exceeds precipitation in a basin. We calculate that by 2060, backsim31{\%}–35{\%} of the global population will be exposed to >50{\%} probability of hydroclimatic deficit increases that exceed existing hydrological storage, with up to 9{\%} of people exposed to >90{\%} probability. However, internal variability, which is an irreducible uncertainty in climate model predictions that is under-sampled in water resource projections, creates substantial uncertainty in predicted exposure: backsim86{\%}–91{\%} of people will reside where irreducible uncertainty spans the potential for both increases and decreases in sub-annual water deficits. In one population scenario, changes in exposure to large hydroclimate deficits vary from −3{\%} to +6{\%} of global population, a range arising entirely from internal variability. The uncertainty in risk arising from irreducible uncertainty in the precise pattern of hydroclimatic change, which is typically conflated with other uncertainties in projections, is critical for climate risk management that seeks to optimize adaptations that are robust to the full set of potential real-world outcomes.",
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Mankin, JS, Viviroli, D, Mekonnen, M, Hoekstra, AY, Horton, RM, Smerdon, JE & Diggenbaugh, NS 2017, 'Influence of internal variability on population exposure to hydroclimatic changes' Environmental research letters, vol. 12, no. 4, 044007, pp. -. https://doi.org/10.1088/1748-9326/aa5efc

Influence of internal variability on population exposure to hydroclimatic changes. / Mankin, Justin S.; Viviroli, Daniel; Mekonnen, Mesfin; Hoekstra, Arjen Ysbert; Horton, Radley M.; Smerdon, Jason E.; Diggenbaugh, Noah S.

In: Environmental research letters, Vol. 12, No. 4, 044007, 2017, p. -.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Influence of internal variability on population exposure to hydroclimatic changes

AU - Mankin, Justin S.

AU - Viviroli, Daniel

AU - Mekonnen, Mesfin

AU - Hoekstra, Arjen Ysbert

AU - Horton, Radley M.

AU - Smerdon, Jason E.

AU - Diggenbaugh, Noah S.

PY - 2017

Y1 - 2017

N2 - Future freshwater supply, human water demand, and people's exposure to water stress are subject to multiple sources of uncertainty, including unknown future pathways of fossil fuel and water consumption, and 'irreducible' uncertainty arising from internal climate system variability. Such internal variability can conceal forced hydroclimatic changes on multi-decadal timescales and near-continental spatial-scales. Using three projections of population growth, a large ensemble from a single Earth system model, and assuming stationary per capita water consumption, we quantify the likelihoods of future population exposure to increased hydroclimatic deficits, which we define as the average duration and magnitude by which evapotranspiration exceeds precipitation in a basin. We calculate that by 2060, backsim31%–35% of the global population will be exposed to >50% probability of hydroclimatic deficit increases that exceed existing hydrological storage, with up to 9% of people exposed to >90% probability. However, internal variability, which is an irreducible uncertainty in climate model predictions that is under-sampled in water resource projections, creates substantial uncertainty in predicted exposure: backsim86%–91% of people will reside where irreducible uncertainty spans the potential for both increases and decreases in sub-annual water deficits. In one population scenario, changes in exposure to large hydroclimate deficits vary from −3% to +6% of global population, a range arising entirely from internal variability. The uncertainty in risk arising from irreducible uncertainty in the precise pattern of hydroclimatic change, which is typically conflated with other uncertainties in projections, is critical for climate risk management that seeks to optimize adaptations that are robust to the full set of potential real-world outcomes.

AB - Future freshwater supply, human water demand, and people's exposure to water stress are subject to multiple sources of uncertainty, including unknown future pathways of fossil fuel and water consumption, and 'irreducible' uncertainty arising from internal climate system variability. Such internal variability can conceal forced hydroclimatic changes on multi-decadal timescales and near-continental spatial-scales. Using three projections of population growth, a large ensemble from a single Earth system model, and assuming stationary per capita water consumption, we quantify the likelihoods of future population exposure to increased hydroclimatic deficits, which we define as the average duration and magnitude by which evapotranspiration exceeds precipitation in a basin. We calculate that by 2060, backsim31%–35% of the global population will be exposed to >50% probability of hydroclimatic deficit increases that exceed existing hydrological storage, with up to 9% of people exposed to >90% probability. However, internal variability, which is an irreducible uncertainty in climate model predictions that is under-sampled in water resource projections, creates substantial uncertainty in predicted exposure: backsim86%–91% of people will reside where irreducible uncertainty spans the potential for both increases and decreases in sub-annual water deficits. In one population scenario, changes in exposure to large hydroclimate deficits vary from −3% to +6% of global population, a range arising entirely from internal variability. The uncertainty in risk arising from irreducible uncertainty in the precise pattern of hydroclimatic change, which is typically conflated with other uncertainties in projections, is critical for climate risk management that seeks to optimize adaptations that are robust to the full set of potential real-world outcomes.

KW - METIS-322158

U2 - 10.1088/1748-9326/aa5efc

DO - 10.1088/1748-9326/aa5efc

M3 - Article

VL - 12

SP - -

JO - Environmental research letters

JF - Environmental research letters

SN - 1748-9318

IS - 4

M1 - 044007

ER -