Science - USA (2021-11-12)

SCIENCE science.org 12 NOVEMBER 2021 • VOL 374 ISSUE 6569 795

EDITORIAL

PHOTO: UCLA SCHOOL OF LAW

A

s alarm about climate change and calls for

action intensify, solar geoengineering (SG) is

seeing increased attention and controversy.

Views on whether it should or will ever be

used diverge, but the evidentiary basis for

these views is thin. On such a high-stakes,

knowledge-limited issue, one might expect

strong support for research, but even research has

met opposition. Opponents’ objections are ground-

ed in valid concerns but impossible to fully address,

as they are framed in ways that make rejecting re-

search an axiom, not a conclusion based on evidence.

Supporters of SG research argue that it can inform

future decisions and prepare for likely future calls for

deployment. A US National Academies of Sciences,

Engineering, and Medicine (NASEM) report earlier

this year lent thoughtful support to this view. Oppo-

nents raise well-known concerns about SG such as its

imperfect climate correction,

its time-scale mismatch with

greenhouse gases (GHGs), and

the potential to over-rely on it

or use it recklessly or unjustly.

They oppose research based on

the same concerns, arguing that

usage can never be acceptable

so research is superfluous; or

that sociopolitical lock-in will

drive research toward deploy-

ment even if unwarranted. Both

support and opposition are of-

ten implicit, embedded in debates over additional gov-

ernance of SG research beyond peer review, program

management, and regulatory compliance.

At present, potential SG methods and claimed ben-

efits and harms are hypothetical, not demonstrated.

The strongest objections to research invoke potential

consequences that are indirect, mediated by imprudent

or unjust policy decisions. Because the paths from re-

search to these bad outcomes involve political behav-

ior, claims that these “could” happen cannot be fully

refuted. Understanding and limiting these risks require

the same research and governance-building activities

that opponents reject as causing the risks.

To reject an activity based on harms that might fol-

low is to apply extreme precaution. This can be war-

ranted when there is risk of serious, unmitigable harm

and the alternative is known to be acceptable. That is

not the case here. Rejecting SG research means taking

the alternative trajectory of uncertain but potentially

severe climate impacts, reduced by whatever emissions

cuts, GHG removals, and adaptation are achieved. But

these other responses needed to meet prudent climate

targets carry their own risks: of falling short and suffer-

ing more severe climate change, and of collateral envi-

ronmental and socioeconomic harms from deployment

at the required transformative, even revolutionary, scale.

Suppressing research on SG might reduce risks from

its future use, but this is not assured: Rather than pre-

venting use in some future crisis, blocking research

might make such use less informed, cruder, and more

dangerous. Even if these risks are reduced, this would

shift increased risks onto climate change and crash pur-

suit of other responses. Total climate-related risk may

well increase—and be more unjustly distributed, be-

cause the largest benefits of SG appear likely to flow to

the most vulnerable people and communities.

Yet the concerns that motivate opposition to research

are compelling. SG use would be an unprecedented

step, affecting climate response,

international governance, sus-

tainability, and global justice.

Major concerns—about reckless

or rivalrous use, or over-reliance

weakening emissions cuts—are

essential to address, even if they

cannot be avoided with certainty.

A few directions show promise

for doing so. Research should

be in public programs, in juris-

dictions with cultures of public

benefit and research accountabil-

ity. The NASEM call for a US federal program is sound.

Other national programs should be established. Research

governance should be somewhat stronger than for less

controversial research, including scale limits on field ex-

periments and periodic program reassessments. Explora-

tion of governance needs for larger-scale interventions

should begin well before these are considered. Research

and governance should seek broad international coop-

eration—promptly, but not as a precondition to national

programs. Broad citizen consultations are needed on

overall climate response and the role of SG. These should

link to national research and governance programs but

not have veto power over specific activities.

Precaution is appropriate, even necessary. But pre-

caution cannot selectively target risks from one climate

response while ignoring its linkages to other responses

and risks. Suppressing SG research is likely to make the

harms and injustices that opponents fear more likely,

not less.

–Edward A. Parson

Geoengineering: Symmetric precaution

Edward A. Parson

is Dan and Rae

Emmett Professor

of Environmental

Law and Faculty

Director of the

Emmett Institute

on Climate Change

and the Environment

at the University

of California, Los

Angeles, CA, USA.

[email protected]

10.1126/science.abm

“...objections are...

framed in ways

that make rejecting

research an axiom...”