Adapting to a 4°c world
| Date | 01 March 2022 |
| Author | Karrigan Bork, Karen Bradshaw, Cinnamon P. Carlarne, Robin Kundis Craig, Sarah Fox, Josh Galperin, Keith Hirokawa, Shi-Ling Hsu, Katrina Kuh, Kevin Lynch, Michele Okoh, Jessica Owley, Melissa Powers, Shannon Roesler, J.B. Ruhl, James Salzman, David Takacs, and Clifford J. Villa |
32022 ENVIRONMENTAL LAW REPORTER 52 ELR 10211
by Karrigan Börk, Karen Bradshaw, Cinnamon P. Carlarne, Robin Kundis Craig,
Sarah Fox, Josh Galperin, Keith Hirokawa, Shi-Ling Hsu, Katrina Kuh, Kevin Lynch,
Michele Okoh, Jessica Owley, Melissa Powers, Shannon Roesler, J.B. Ruhl,
James Salzman, David Takacs, and Clifford J. Villa
SUMMARY
The Paris Agreement’s goal to hold warming to 1.5°-2°C above pre-industrial levels now appears unreal-
istic. Profs. Robin Kundis Craig and J.B. Ruhl have recently argued that because a 4°C world may be likely,
we must recognize the disruptive consequences of such a world and respond by reimagining governance
structures to meet the challenges of adapting to it. In this latest in a biannual series of essays, they and other
members of the Environmental Law Collaborative explore what 4°C might mean for a variety of current legal
doctrines, planning policies, governance structures, and institutions.
ADAPTING TO A 4°C WORLD
Participants at the Environmental Law Col laborative’s
(ELC’s) most recent meeting in July 2021 were asked
to consider the adaptation challenges of the worst-
case climate scenario: a world that warms by 4 degrees
Celsius (°C) (or more) by 2100. As environmental law
professors, we remain dedicated to the study and support
of laws and policies designed to mitigate greenhouse gas
(GHG) emissions and avert the worst-case scenario. But
we cannot ignore what scientic studies and newer climate
models show. e Paris Agreement’s goal to hold warming
to 1.5°-2°C above pre-industrial levels now appears unreal-
istic.¹ In the United States, regulatory in action and political
gridlock frustrate e orts to implement the decarbonization
measures that we need now to prevent the warming pre-
dicted by climate models. At the international level, the
commitment and cooperation necessary for dra matic emis-
sions reductions also appear unlikely.
To frame and inspire discussion about the consequences
of a 4°C world, participants read a recent article by two
ELC members, Robin Kundis Craig and J.B. Ruhl, who
1. For a summary of the Paris Agreement and links to the document, see
United Nations Climate Change, T P A, https://unfccc.
int/process-and-meetings/the-paris-agreement/the-paris-agreement (last
visited Jan. 6, 2022).
argue that because a 4°C world is likely, we must recognize
the disruptive consequences of such a world and respond by
reimagining governance structures to meet the challenges
of adaptation.² A 4°C world is one marked by dramatic
sea-level rise, devastating heat waves, extreme drought,
increased ooding, food insecurity, and radical shifts in
ecosystems and biodiversity. Some communities may not
be able to adapt; they may simply have to move. Adapting
our laws and governance structures to physical and social
disruption at this scale requires transformative thinking.
In the essays that follow, ELC participants explore what
it means to adapt to a 4°C world. Some essays highlight
the inadequacy of current legal doctrines, planning poli-
cies, and governance structures to meet the adaptation
challenges ahea d. Others examine the need to rethink laws
and institutions that govern ecosystem services and issues
of biodiversity. And some focus on issues of social equity
and environmental injustice. Although each essay makes
its own contribution, they all share a deep concern for the
future and an urgency to mitigate not only the emissions
that drive us closer to 4°C, but also the serious harms that
we will suer if we fail to plan for the worst-case scenario.
I. Western Water Rights in a 4°C Future
is section was authored by Kevin Lynch, Associat e Professor of
Law with Tenure, Sturm College of Law, University of Denver;
Shi-Ling Hsu, D’Alemberte Professor of Law, Florida State
University College of Law; and Karrigan B örk, Acting Professor
of Law, University of California, Davis School of Law.
Western water rights reect a short and stable climate his-
tory, but that period of stability is ending. Looming climate
2. J.B. Ruhl & Robin Kundis Craig, 4°C, 106 M. L. R. 191 (2021).
Authors’ Note: The Environmental Law Collaborative (ELC)
comprises a rotating group of law professors who as-
semble every other year to think, discuss, and write on an
important and intriguing theme in environmental law. The
goals of this meeting are both scholarly and practical, as
ELC participants seek to use their disparate areas of schol-
arly expertise to study trends and important events in the
law and ultimately to improve the environmental conditions
of the world in which we live.
Copyright © 2022 Environmental Law Institute®, Washington, DC. Reprinted with permission from ELR®, http://www.eli.org, 1-800-433-5120.
52 E LR 10 212 ENVIRONMENTAL LAW REPORTER 32022
change of 4°C will produce not only higher temperatures,
but decreased snowpack, shifts in runo patterns,³ and
the dramatic shrinkage of giant reservoirs. e climatic
changes that have already traumatized the West will only
intensify and cross even more dangerous th resholds, neces-
sitating the deliberate adaptation of water rights systems.
A. Hydrology in a Changing Climate
A climate-changed future is inherently uncertain, but the
general consensus predicts a dire future for water sup-
ply in the arid West. Precipitation patterns are the big-
gest source of uncertainty, due to the potential increase
in extreme weather events. is could both increase and
decrease water supplies as larger snowstorms could dump
more precipitation in some years, while other impacts on
the snowpack would lead to declines. However, higher
temperatures in the summer and fall are expected to oset
potential increases in snowpack in most years, leading to
an overall trend of less water supply in a warming future.
Temperature increases along the Colorado River may
reduce ows by more than 20% mid-century and 35% by
2100, reducing vital water supplies to seven states and 23
tribal nations.
Intra- and inter-annual variability will continue as a
hallmark of western water systems. In the Colorado River
basin, for example, the impacts of a changing climate are
already apparent as the current megadrought fueled by
climate change recently led to the rst ever federal water
shortage declaration.¹ Experts urge us to plan for even
worse impacts to come.¹¹
Looking beyond the Colorado River basin, a 4°C world
leads to large declines in snowpack in the western United
States, perhaps in the range of a 40% decrease due to gen-
3. Abigail C. Lute et al., Projected Changes in Snowfall Extremes and Interannual
Variability of Snowfall in the Western United States, 51 W R. R.
960, 969-70 (2015).
4. Jaweed Kaleem & omas Curwen, “Unrecognizable.” Lake Mead, a Lifeline
for Water in Los Angeles and the West, Tips Toward Crisis, L.A. T (July 11,
2021, 5:01 AM), https://www.latimes.com/world-nation/story/2021-07-11/
lake-mead-hoover-dam-drought-nevada-arizona-california.
5. Hervé Douville et al., Water Cycle Changes, in C C 2021: T
P S B. W G I C S
A R I P C
C 8-1, 8-96, 8-119 to 8-121 (Valérie Masson-Delmotte et al. eds.,
Cambridge Univ. Press 2021).
6. Linda O. Mearns et al., e North American Regional Climate Change Assess-
ment Program: Overview of Phase I Results, 98 B. A. M
S’ 1337, 1358-59 (2012).
7. Bradley Udall & Jonathan Overpeck, e Twenty-First Century Colorado
River Hot Drought and Implications for the Future, 53 W R. R.
2404, 2414-15 (2017).
8. Id. at 2404.
9. Water Education Foundation, Colorado River, https://www.watereducation.
org/aquapedia/colorado-river (last visited Jan. 6, 2022).
10. Kirk Siegler, Colorado River, Lifeline of the West, Sees Historic Water Short-
age Declaration, NPR (Aug. 22, 2021, 5:13 PM), https://www.npr.org/
2021/08/22/1030154245/colorado-river-lifeline-of-the-west-sees-historic-
water-shortage-declaration.
11. John Fleck & Brad Udall, Managing Colorado River Risk, 372 S 885,
885 (2021), available at https://www.science.org/doi/epdf/10.1126/sci-
ence.abj5498.
erally less precipitation and shifts from snow to rain.¹² e
snowpack in the Sierra Nevada mountains recently hit
its lowest point going back at least 500 years.¹³ Decreas-
ing snowpack reduces water availability throughout hot,
dry summers, resulting in signicant seasonal water short-
ages. One recent study even projects that critical mountai n
ranges in the western United States may lose their snow-
packs for years at a time by mid-centur y.¹
Warmer temperatures and less frequent precipitation
also mean that even normal snowpacks do not necessarily
bring relief from droughts. For example, Colorado’s 2021
snowpack was almost normal, but because soils in many
western watersheds were unusually dry, most of the water
went into the soils and not into streams, rivers, and res-
ervoirs for human uses.¹ Another driver of drought in a
warming world is the increase in evap otranspiration caused
by higher temperatures as plants need more water and
evaporation from rivers and reservoirs increases.¹ ese
factors point toward a drying and warming future in the
southwestern United States, particularly in the Colorado
River basin.
B. Water Law Historically Adapted to Hydrology
e changes in the West’s hydrology are very likely to pro-
duce changes in water law, which has historically evolved
in response to diering climatic conditions.¹ Early U.S.
water law decisions¹ drew heavily on English water law,
establishing a system ba sed on riparian water rights. Ripar-
ian rights come from ownership of land that abuts a water-
course, and they are generally limited to reasonable use of
the water on the riparian land. Riparian rights have many
other limits; they do not allow storage or long-distance
transportation of water, for example, and they are not abso-
lute, leading to some uncertainty about the quantity and
reliability of water. ese limitations meant that riparian
rights were poorly suited to western hydrologic regimes,
where seasonal (and total) water availability patterns
12. David R. Easterling et al., Precipitation Change in the United States, in C-
S S R: F N C A,
V I 207, 218 (Donald J. Wuebbles et al. eds., U.S. Global Change
Research Program 2017), https://science2017.globalchange.gov/down-
loads/CSSR_Ch7_Precipitation.pdf.
13. Soumaya Belmecheri et al., Multi-Century Evaluation of Sierra Nevada
Snowpack, 6 N C C 2, 2 (2016), available at https://
www.nature.com/articles/nclimate2809.pdf.
14. Erica R. Siirila-Woodburn et al., A Low-to-No Snow Future and Its Impacts
on Water Resources in the Western United States, 2 N R. E
E’ 800 (2021), available at https://www.nature.com/articles/s43017-
021-00219-y.epdf.
15. Miguel Otárola, Colorado’s Snowpack Was Almost Normal is Winter, but It
May Not Be Enough Water for the Year, CPR N (Apr. 2, 2021), https://
www.cpr.org/2021/04/02/colorados-snowpack-was-almost-normal-this-
winter-but-it-may-not-be-enough-water-for-the-year/.
16. Michael F. Wehner et al., Droughts, Floods, and Wildres, in C S-
S R: F N C A, V
I, supra note 12, at 231, 232, 236-39, 247, https://science2017.global-
change.gov/downloads/CSSR_Ch8_Drought_Floods_and_Wildres.pdf.
17. Joseph W. Dellapenna, United States: e Allocation of Surface Waters, in
T E L P W 189, 189 (Joseph W.
Dellapenna & Joyeeta Gupta eds., Springer 2009).
18. See, e.g., Tyler v. Wilkinson, 24 F. Cas. 472 (C.C.D.R.I. 1827) (No. 14,312).
Copyright © 2022 Environmental Law Institute®, Washington, DC. Reprinted with permission from ELR®, http://www.eli.org, 1-800-433-5120.
To continue reading
Request your trial