Risk from Nuclear Weapons Use:

A Systems’ Perspective

Reinhard Mechler

International Institute for Applied Systems Analysis (IIASA)

Vienna University of Economics and Business (WU)

Session II – Risk Drivers for Deliberate or Inadvertent Nuclear

Weapons Use

December 8, 2014

Risks from Nuclear Weapons Use:

A Systems’ Perspective

• Presentation adds a systems’ analysis perspective to the discussion

o Propagation of consequences across natural and social systems

o Persistence and irreversibility

o Feedbacks

• Roles of risk and resilience

– Risk propagation through lack of resilience - systems’ ability to buffer against

shocks

– Risk avoidance vs. risk acceptance

• Mapping out the scenario space:

What can be said about the limited exchange and local scenarios in

terms of their drivers of risk and resilience as well as their

consequences?

Biological systems research

Technological systems research

Geographical systems research

Social systems research

Entry point: Systems’ Analysis as part of Sustainability Science

Understanding life support

systems to maintain

human well-being

Based on NRC, 1999

Sustainability

science

Systemic Risk Assessment

Social and physical

subsystem

Systems’

resilience

Casualties

Nuclear

threat

Firestorms

Atmospheric

cooling Climate

system

Food

security

Migration

Responses:

Individual-collective

Local-international

Local

Regional Global

Indirect Impacts: Climate Anomaly through Large Soot

Release

Tambora, 1816:

Year without a summer Mills, 2014

IPCC, 2013

Climate consequences of a limited exchange

Years

Temperature reconstruction – more than 1000 years

Brönnimann, & Hadorn,

2013

• Concern is also with climate variability, not merely warming

• Good evidence that socio-economic resilience to deal with

shocks limited:

o Climate change poses large threats to regional and global

food security, as agricultural systems cannot sustain food

production

o Climate change projected to increase displacement of

people

• Nuclear risk as very fast-paced change with limited time for

response and coping

Insights from Climate Change Research

Food Security & Resilience (IPCC, 2014)

APPROVED SPM – Copyedit Pending IPCC WGI I AR5 Summary for Policymakers

WGII AR5 Phase I Report Launch 39 31 March 2014

Assessment Box SPM.1 Figure 1.

Summarizing the Evidence

IPCC, 2014

• 1992: Climate Convention

(UNFCCC) Art. 2:

Prevent dangerous

anthropogenic interference

with the climate system.

• 2010: Climate Summit, Cancun:

Limit warming to 2 oC!

• 2 degrees target imposed by

policymakers, not scientists

IPCC’s 5 Reasons for Concern, 2001

Sce

nar

io

Risks from Nuclear Warfare

Reasons for Concern

Local

Global

Impacts on

Systems

Health

direct Agro-ecological

Health

indirect Climate Social

Propagation importantly determined by

physical and socio-economic systems’ resilience

Sce

nar

io

1 H bomb in

megacity

Thousands of

H bombs

Well studied in 1960s, 70s and 80s [Ayres, 1965; Batten, 1966; NRC, 1975; Crutzen and Birks, 1982;

Aleksandrov and Stenchikov, 1983; Turco et al., 1983, 1990; Robock, 1984;

Pittock et al., 1986; Harwell and Hutchinson, 1986; Sagan &Turco, 1990] Indirect effects of a large- scale nuclear war would probably be far

more consequential than the direct effects

Since 2000s local and regional scale in focus

[Toon et al., 2007; Robock et al., 2007; O ̈zdog ̆an, 2012; Xia and

Robock, 2012; Stenke et al., 2013; Helfand, 2013; Mills et al., 2014]

Increasing understanding for climate and indirect effects.

100

H bombs

Risks from Nuclear Warfare

Reasons for Concern

Impacts on

Systems

Health

direct Agro-ecological

Health

indirect Climate Social

Nuclear winter

Global ozone

losses

Prolonged cold

phase: 25 years

Sce

nar

io

1 H bomb in

megacity

Thousands of

H bombs

100

H bombs

0.7 * 109

fatalities

0.3-2 * 107

fatalities

1-7 * 105

fatalities

1-4 * 109

fatalities

1 * 109

fatalities

Radiation

fallout

Massive food

crisis

Food crisis

and hoarding

Collapse of

civilization

Panic and mass

migration

Key gaps in

humanitarian

response leading

to displacement

Risks from Nuclear Warfare

Reasons for Concern

Impacts on

Systems

Health

direct Agro-ecological Social

Health

indirect Climate

Sce

nar

io

1 H bomb in

megacity

100

H bombs

Risks from Nuclear Warfare

Reasons for Concern

Impacts on

Systems

Health

direct Agro-ecological Social

Health

indirect Climate

Thousands of

H bombs

Summary

• Cursory review and visualization of evidence to map out the scenario space

o Global exchange: Massive global consequences well understood since

1970s and 1980s

o Limited exchange: New evidence suggests consequences are global,

persistent and irreversible

o Single event/terrorism: Consequences can be very large if megacities

targetted and if amplified by gaps in humanitarian response

• Across scenarios, resilience is very limited across climate, agro-

ecological, health and social systems

• Narrow limits for building resilience against nuclear warfare risk

• Scope and degree of indirect and persistent impacts shows we

are dealing with unacceptable risk