INSIGHTS | POLICY FORUM
courts in their decisions varied, depending
on, e.g., the climate topic in the case, the law
being challenged (see the figure), and the
identity of the litigants bringing the cases
(e.g., pro- or antiregulation; nongovernmental organization, state, or industry association). Generally, science is raised more in
cases brought with a proregulatory goal than
with an antiregulatory goal.
Courts address climate and other kinds of
science at relatively similar rates over time,
and the level of science used in cases has
been increasing (fig. S1). Many climate cases
do not use science, such as cases decided on
legal or administrative grounds that do not
implicate science [e.g., the Supreme Court’s
2011 decision in American Electric Power Co.
v. Connecticut, resolved on the basis of inquiries into Congress’s intent when it passed the
Clean Air Act (CAA)].
Analysis of a subsample of the cases demonstrates how the courts have used science
in certain kinds of cases. In the case of biodiversity issues, proregulatory cases have been
able to rely on well-developed science on the
impacts of climate change on species, habitats, and ecosystems. In energy cases, litigants have introduced information regarding
energy infrastructure and the costs associated with distinct energy trajectories.
In cases involving government decision-making, such as environmental impact review, courts do not conduct trials in which
they receive new evidence. Instead, they
review the legality of an agency’s decisions
based on the administrative record compiled
by the agency in the course of its decision-making process. An important component of
judicial review is determining whether the
administrative record contains a sufficient
evidentiary basis to support the administrative decision. If it does not, a court may invalidate the action as “arbitrary or capricious”
decision-making. If prospective litigants
want to challenge the adequacy of the agency’s consideration of climate science, they
must submit scientific evidence in support
of their position well before litigation begins,
e.g., when agencies invite comments from the
public responding to proposed rules or draft
versions of environmental impact statements
or biological opinions.
IMPLICATIONS FOR SCIENCE IN COURT
There are several key takeaways from this re-
search. One is that the relevance of science is
context-specific and changing. Although only
two-fifths of the cases we surveyed implicated
climate science, seemingly indicating that the
state of science is less important than other
factors, decisions in more recent cases have
tended to explore climate science more thor-
oughly than in earlier cases. For example,
litigants have been relatively successful in in-
ducing courts to focus on climate science in
cases alleging violations of the National Envi-
ronmental Policy Act (NEPA) or the ESA. The
issue in these cases is whether the agency
took adequate account of climate science in
making a decision such as approval of a pro-
posed project that may affect ecosystems or
species already under climate-related threat.
Our database includes too few common-law nuisance cases, which involve judge-made doctrines rather than decisions by
administrative agencies or that depend on
environmental statutes, to allow us to draw
meaningful conclusions about the importance of science in these cases. However, it is
likely that plaintiffs in tort actions will find it
difficult based on currently available science
to trace alleged climate-related personal injuries or property damage to the actions of
particular defendants. This may change as
climate science continues to develop (such
as science that could “fingerprint” the harms
linked to specific GHG emissions), but the
likelihood that this shift will occur in the
near term is small.
Another takeaway of this research is that
novel legal theories are emerging in an effort
to use available climate science in ways that
increase the likelihood of success. Litigants in
cases outside of the United States have used
novel theories such as international human
rights law, international treaties, and domestic constitutional law (9–12). In the Urgenda
case from the Netherlands, a district court
ordered the Dutch government to take steps
to substantially reduce GHGs based on a series of decisions of the Dutch Supreme Court
holding that government can be legally accountable for failure to prevent foreseeable
harms to its citizens. Among other things, the
court relied on climate science to define the
percentage reduction in GHG emissions the
government would need to achieve to avert
imminent dangers linked to climate change.
More recently, the Children’s Trust cases
in the United States have invoked the public trust doctrine and due process theories to
argue that U.S. states are responsible for protecting children from the impacts of climate
change. Litigants have avoided dismissal of
their claims in preliminary decisions in the
lower courts in two of these cases, and similar suits are pending throughout the country.
The federal district court in Oregon relied on
climate science to hold that the plaintiffs had
standing to sue and in ruling that the plain-
tiffs’ complaint included sufficient allegations
about climate impacts to allow a substantive
due process claim to proceed.
We suspect that climate change litigation
is likely to increase if the Trump Administration continues to rescind protections adopted
by the Obama Administration, particularly
those based on EPA’s regulatory authority
under the CAA, or others such as the recent executive order that removed President
Obama’s mandate to consider climate change
in infrastructure planning. Climate litigation
in the short term can be expected to focus on
the role that climate science should play in
government decision-making. In addition, a
spate of litigation is likely if federal agencies
ignore or give short shrift to climate effects
in evaluations conducted to comply with
NEPA and ESA. For example, a 2017 executive
order from President Trump withdrew the
guidance to federal agencies provided by the
Council on Environmental Quality in 2016 on
how to incorporate climate considerations
into NEPA analyses. Litigants in such cases
would need to muster scientific support for
their claims that agencies arbitrarily ignored
Industry is likely to push back against proregulatory climate policies and actions, such
as in California. One way for them to do so
will be to argue that climate science does not
support the state’s identification of climate
threats or harms or its choice of strategies
to address those harms. In many cases, the
fate of both proregulatory and antiregulatory lawsuits is likely to turn on the strength
of the scientific evidence that litigants are
able to produce in the administrative record
concerning the causes and effects of climate
change and the ability of chosen solutions
to address those effects. We think it is likely
that as climate scientists become more able
to attribute specific events to human-induced
climate change, judges will increasingly
object to government decisions they regard
as having afforded insufficient consideration
of available climate science. j
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“…novel legal theories are
emerging in an effort to use
available climate science…”