Scientific uncertainty and decision making: The case of greenhouse gases and global climate change

The Science of the Total Environment, 55 (1986) 177--186 Elsevier Science Publishers B.V., A m s t e r d a m -- Printed in The Netherlands

177

SCIENTIFIC UNCERTAINTY AND DECISION MAKING: THE CASE OF GREENHOUSE GASES AND GLOBAL CLIMATE CHANGE

J.A. LAURMANN Gas Research Institute~ 8600 W. Bryn Mawr Ave.,

Chicago IL 60631

(USA)

ABSTRACT A number of issues that relate analytic study of the climatic consequences of increasing anthropogenic release of greenhouse gases to environmental policy are raised. We discuss in particular the role of uncertainty of information in the context of the long term global and potentially massive nature of the threat. Some r e c o ~ e n d a t i o n s are made for new lines of study to determine the degree of urgency of the problem and the proximate need for remedial measures and the difficulties of their implementation.

INTRODUCTION Even though the most recent solid scientific reviews on the subject (ref.l,2)

conclude

that there is no near term need to reduce anthropogenic

release of CO 2 emissions

into the atmosphere,

consideration be given to the proposition The basis

it is important that serious

that this evaluation

is incorrect.

for the assertion is that infra-red absorbing trace gases, additional

to CO2, will double the climatic warming due to CO 2 alone (ref.3,4)), resulting

in an average global temperature rise of 3°C in about the year

2025 (ref.l),

and that ameliorative

action through a move away from the present

predominant use of fossil energy to non-carbon based sources could take 50 to I00 years

to take effect (ref.5,6,7).

Additionally,

it is likely that the

greenhouse gas induced warming may be delayed between 20 and I00 years, due to upper ocean layer thermal inertia (ref.8,9).

If the latter is the case, and

if responsive measures are taken only when definitive correlation can be established between observed climatic change and atmospheric greenhouse gas levels,

an irreversible and potentially calamitous

temperature rise could

eventually occur (ref.lO). • Furthermore, effect,

large uncertainty

in all aspects of the chain of cause and

starting with future trace gas emission estimates and concluding with

economic and social impacts of climatic change, tion.

A significant probability

earlier and be of larger magnitude cited above.

than indicated by the best guessed estimate

To make matters worse,

0048-9697/86/$03.50

are a major source of complica-

therefore exists that impacts can occur

it appears that this uncertainty will not

© 1986 Elsevier Science Publishers B.V.

178 be much reduced

in the near future,

The fact that definitive cost-effective

means

statements

the need and means

for large climate perturbations. the proximity

for its remediation

yet no clear observational trace gas emissions,

especially concerning

evidence

it is logical

to the pragmatic question of assessing

to the possible

from that most often used in treating

allows

cannot be made, and that there is as

for a climatic change associated with

implies an approach for responding

scientific

to develop an action oriented

for the uncertainties

of the threat and

threat that is different problems.

decision-making

in our current knowledge,

In this situation viewpoint

that

and it is this theme

with which the paper is concerned. Several other present day environmental characteristics,

so we in fact have a modest background

on, though many extreme.

and health problems exhibit

features of the greenhouse

It is also important

to objectively

to rationally

to note that to date the greenhouse

environmental

discuss global remediation

apply the decision-making

of politically

motivated problems

shall briefly outline change/greenhouse

biases

in the use of analytic approaches counter

the potential

procedures

discussion

crossing national boundaries. the role of uncertainty

gas problem

so we still have the

tools available without

that dominate

gas environmental

to rely

gas problem are unique as well as

is not regarded as major by any national government, opportunity

of experience

similar

and attempt the intrusion

of other present day

In the following we

in the climatic

problem and see where we currently

for deciding

stand

if, when and how to act to

threat.

PHYSICAL BACKGROUND It is traditional disciplinary a.

to divide

the greenhouse

gas problem into the following

categories:

Economic

development

and energy use projections;

b.

CO 2 and other trace gas emissions;

c.

Carbon cycle modeling

d.

Models

e.

Physical models

other greenhouse

specialty

in modeling

for the

gases has yet been developed);

that compute

hydrosphere

(no corresponding

the trace gas effects on global climate;

for evaluating

the response

of the biosphere

to climatic change and increasing concentrations

and of the

emissions; f.

Estimation

of the economic and societal costs of these effects;

We have estimates

on both magnitudes

first four of these categories quantitative

information

and errors of projections

(ref.l,3,11)

on the last two.

for the

and a modest amount of A few crude estimates

costs have been made, but we have no idea as to their accuracy.

of impact The

179 importance problem

of uncertainty

is illustrated

Cumulative Probability % 100

I

in judging

I

i

of the environmental

~L,,===eses==~-~ ~

(

80 -

the seriousness

in Fig. i.

60 /~ 40

20 o

(1): C02 Emission Error i2i." (1) + Climate Model Error (3): (1) + (2) + Other Trace Qas Error

~ Ir/ ~

I

0

I

2

Fig. i

I

i

I

I

_ -

4 6 8 10 12 Annual Capital Asset Loss, % of QWP

14

Cumulative probability distributions of annual global capital asset loss as a percentage of gross world product.

This plots the effect of current estimates

of uncertainty

on the cumulative

of annual capital asset loss rate

as a percentage

arising

the other errors. decision making, when applied definitive

No allowance

The information since personal

to the probability

concerning

change,

considerable

(GWP).

the contribution the results

costs at only slightly

application

for

shown in the figure9 yields an costs.

in Fig. 1 arises

from

of gases other than CO 2 to indicate

the possibility

lower probability

value for the "best guessed"

estimate

of very

levels than the 50%

of 3% of gross world product

there is a chance of i in 4 that costs can exceed 10% of

is due to assumptions

(ref.12).

for

larger than any of

choice of a given level of risk acceptability estimates

the largest error contribution

and overall

For example~

a quadratic

is made in the calculations

in Fig. 1 can be a useful adjunct

GWP by 2025 (curve 3 in the figure). curves

rise from all trace gas

impact cost that can be compared with remediation

uncertainties

cumulative

temperature

from items e and f, which are certainly

As is to be expected,

climatic

in items a through d

in the year 2025 (at this date the

is that the equilibrium

will be 3°C).

uncertainty

distribution

of gross world product

latest best guess emissions

probability

dependence

of climatic

The importance

The strong asymmetry of the distributions

of log normal errors

in all the variables

impact costs on temperature

of non-linearity

of the decision analytic

is seen particularly

approach~

and of

increase clearly

as we shall discuss next.

through

180

IMPACT EVALUATION Decision analysis

is a formalized

drawing policy-oriented environmental

conclusions~

control measures

the effectiveness

to parametric

variations.

details of the method tion by observing uncertainty

for allowing

in practical

for determining

but we can sunm~arize

that 9 with its use~ the ambiguity

is eliminated by associating

a weight

for (in our case) cost of the impact.

the weighting results

function that defines

and then nearly always

of risk decreases

or in economic

in a risk averse utility

(ref.ll)).

The non-linear

manner are different uncertainties, increased.

i.e., the economic

Fig. 2 illustrates

loss costs of climatic

this point.

to calculations

averse utility ref.12).

function

threat are

Here we have plotted capital asset

growing at 3% per annum.

for uncertainty,

The two curves

averaging

and on a risk

(details of the latter are to be found in

At the CO 2 doubling date - about 2040 in this scenario - risk

% Qross World Product

I 15

,

,

,

,

1980

2000

2020

2040

, / , / ,

-

10

5

0 2060

in this

that ignore the

of the environmental

based on simple unweighted

formulation

function

costs derived

than mean estimates

consequences

out of propor-

as decreasing

change as a function of time~ allowing

but including only CO 2 emissions, correspond

terms~

weighting means that expected

(normally higher)

of

to yield a single "expected

tion with cost at high cost levels)~ (which also results

for

its critical contribu-

marginal

utility

sensitivities

to each level of probability

grounds,

(acceptance

Even though

caused by the presence

The utility

is either chosen on behavioral

in "risk averse" behavior

in

can be questioned,

to other expositions

of an event (such as shown in Fig. i) and averaging value"

rationale.

situations

to apply as a means

We refer the reader

(ref.ll~13)~

for uncertainty

such as determining when to implement

through a cost/benefit

of the approach

it is at minimum instructive

technique

2080

2100

Fig. 2 Effect of risk aversive behavior on climatic change annual capital estimates.

loss

181

aversity

increases

cost from about 3% to about 7% of gross world product.

should mention here that these estimates9 thermal equilibration change

of the climate

the timing of impacts

rationale

in a major way and hence

significantly

alter

the

i and 2~ although of very dubious quantitative

due to the radical assumptions

nevertheless

made in deriving

in accord with the generally held belief

from CO 2 doubling will have important 3% of GWP (net of inflation) zero~

i~ assume

effects can

for taking remedial actions.

The costs given in Figs. merit~

as well as those in Fig.

system; non-equilibrium

We

an unpleasant~

but presumably

judge the significance must be applied~

impacts.

corresponds

situation.

However~

in today's world~

and this has important

are

change

The median cost estimate

to reducing world economic

bearable

of such results

them (ref.ll)~ that climatic

ramifications~

of

growth to

in order to

future discounting

as illustrated

in

Fig. 3.

% Q r o s s W o r l d Product 1.5 I I

I//

I

I

1

// 1.0

0.5

Fig. 3

I

I

I

I

I

~

1980

2000

2020

2040

2060

2080

Effect of discounting

Here the costs plotted

on estimated

future climatic

in Fig. 2 have been discounted

with the result that present day equivalent

rate is also critical

problem when the costs being compared Considerable

intergenerational

emissions

the next century.

in a cost/benefit

are incurred

analysis

at different

argument has ensued over the years on discounting

public welfare program expenditures

particularly

at 3% and 5% per annum9

costs of the future impacts

relatively modest - below 0.6% of GWP - throughout choice of discount

change costs.

discount

critical

is certainly

factors

(ref.14)

one of these (ref.ll).

of the

times. for government

and the choice of the social or

in such cases.

for long term problems~

stay

The

The situation

and increasing

is

greenhouse

gas

182 REMEDIATION The analysis of climatic cost/benefit

calculations

impact costs can be extended

including remediation

situation can be handled

in detail)

Thus)

technology devised

the most promising

elimination

is via extraction

technology)

and pumping

(ref.15)16).

One specific

since cost data for it are available. to date for CO 2 emission

in smoke stacks)

using existing

scrubber

it to the sea for long term deep ocean storage

Fig. 4 compares

a half of all fossil

measures.

to encompass

the cost of using this process

fuel emissions)

with unmitigated

(capturing about

climatic change costs

for the same fossil fuel use history as in Fig. 2 (again with no other greenhouse extremely

gas increases). expensive

average estimates

indicate

that CO 2 removal is

and does not pay until climate change costs approach

3°C rise corresponding The approximate

The results

to CO 2 doubling

calculations of climatic

the

levels.

illustrated

in Figs. 1-3 imply that the

change costs) when discounted)

yield present day

costs that are too small to merit remedial action today) especially when viewed

in conjunction

% Qross World Product

'o/,

,

with the CO 2 removal costs plotted

,

,

,

in Fig. 4.

y /

,,[ 0

'~RemeOiation in 2020 1980

Fig. 4

2000

2020

2040

2060

2080

2100

Net annual global capital asset costs with and without a 50% CO 2 emission reduction.

Alternative

strategies)

such as a gradual reduction of energy use--specifically

in fossil fuel - via strong conservation

measures

forms of energy (ref. 17)) have not been subjected calculation) results priority needs

and might look more favorable.

and the use of renewable to a similar cost/benefit

All in all) future discounting

in a consensus view that ranks the greenhouse list of environmental

to be tempered)

issues.

However)

as we shall now explain.

gas problem low in the

this optimistic

viewpoint

183 Firstly,

the great uncertainty

and their effects measures,

implies

depending

on attitudes

rises of 3°C and associated century and a significant penetration

time delays

suggest considerable reduction

in estimation

towards risk taking.

probability

especially

of CO 2 reduction policies

in obtaining

a desired

The macro-scale

of the energy/economy

for a mandated~

(ref.7)

level of CO 2 emission

applicability

of the latter

system is also in debate,

rather than a free market driven move away from

fossil energy use, so we are also in uncertain the theory,

early in the next

of much higher costs (Fig. 2), market

for implementation

in the time available.

change magnitudes of preventative

Thus, with temperature

costs of 3% of GWP occurring

difficulty

market characteristic

of climatic

the need for early consideration

50 to i00 years are required

territory here.

for the replacement

to attain a 50% share of the total energy market~

According

non-fossil

to

fuel

current use being mostly

fossil. Secondly, calculations

all the arguments

it is probable decades specie

levels.

to equilibrium In principle,

time to take remedial

warming

However,

steps~

for given atmospheric

if this prediction

temperatures

whose ultimate

If such a delay occurs9

the only way of countering

policy on this only recently appreciated

the offending

above,

the atmospheric

the resultant

gases from the free

The implications

feature of the environmental

the physical

that here,

facts are unsure.

decay rate of trace gas constituents

CO2) , once emissions have ceased,

can be

Hence there

neither of these do we now know

and it must also be emphasized

the other issues discussed

of the greenhouse

action until the trace gases have

impossibly high costs or risks.

have yet to be addressed,

by giving more should ease the

trace gas levels.

air, or induce climate cooling by other means;

particular~

existence

trace gas

equilibrium effect on climate could be

climatic warming will be either to extract

how to do today without

rise earlier,

as real until a firm correlation

and rising

the danger of delaying preventative

extreme.

is correct,

the slower rise in temperature

and as now seems likely,

reached concentrations

As we mentioned

effects can delay the rise by several

estimates

effect will not be accepted

seen between rising exists

climate models.

that non-equilibrium

compared

situation.

given so far are based on temperature

made with equilibrium

is critical~

to

problem

just as in

In (including

and is not yet well known.

POLICY IMPLICATIONS A number of approaches issues where scientific

are available

information

for decision making

is involved:

o

The use of scientific

"experts"

o

Subjective

by the decision maker

o

Relying on public opinion,

assessment

in environmental

184

o

Using probabilistic

o

Using risk/benefit

o

Various combinations

Since the greenhouse requiring near-term

information analyses,

(such as given in Fig. I))

and

of these.

gas problem is not yet deemed a political

action, we are in the fortunate position of being able to

avoid the more tenuous and dubious approaches more systematic,

analytic alternative.

earlier discussion,

listed here,

Still,

that the scientific

and recommend

basic uncertainties

be sure that application difficulty

either.

hurdle

from several sources are so extreme

Continued

international

attempts

to

that we cannot

to apply the method may indeed help,

agreement on policy measures

(for elaboration,

and analyzed

To make matters

of the decision analytic approach will solve our

but further academic work on fundamental methodology Attaining

the

it should be clear from our

information available

date cannot directly answer the degree of urgency question. worse,

issue

see, for example,

initiate a long term dialogue

ref.18),

is surely indicated. also presents

a major

and it would be wise to

involving policy analysts

and policy-makers

study and become acquainted with the problems of implementation

to

of greenhouse

gas control measures.

Even though the need for such measures may not exist

now, a large potential

risk does exist)

and the difficult

geopolitical

start to study of means as to be better prepared

and the global nature of the threat

issues that are involved recommend

for reaching

international

an early

accord on remediation,

to deal with it if required

so

in the future (see

ref.19). Stress on uncertainty research

results

that are not revealed

discounting,

which, when considered

issues that need addressing implies

in highlighting

otherwise.

the need to stress

a number of major areas of

These arise in part from future

in conjunction with the thesis that the

first are those that require earliest actions, the analysis of large climatic

since it is only large future costs that can have meaning decisions.

Reduction of u~certainty

part of the needed research agenda; research elements

in the physical it is important

to research

difficult

themes also emerge

issues that can be involved threats:

those

policy needs,

and

less well defined and more

from the line of argument we have presented.

topics as a start to confronting,

environmental

that this emphasizes

We shall not detail all the

These stress the social sciences and humanities) research

is of course

tasks that follow from this position - some are obvious

from the earlier discussion - but a number of new, difficult

for present day

sciences

that bear most strongly on action-oriented

hence on the degree of urgency question. revisions

impacts and costs)

and we suggest the following

in a generic way)

in treating major,

the very

global

scale,

185 o

The development forms useful

of methods

for describing

for policy analysis

may require early preventative

o

the rational

treatment

environmental

threat.

actions.

of economic

in climate and in energy use forms.

climatic o

Attempt

and social systems

to major climate change.

responses

limits of sustainability

to rapid changes

change concern the rate of consequences

of a new stable

acceptable

climate change.

development concerned

yet we are very doubtful whether

of world conditions

it may be possible

Cross-cultural

studies concerning

attitudes

here with the perceptions

today in order to combat

especially marketing

carbon dioxide,

gas/climate

and regions to pay

greenhouse

gas emissions,

fuel use taxation and the

using information

available

today,

warming problem and its remediation.

as it is by shortage of information perspective

cultures

problems.

cannot tell how far this approach can succeed without

restricted

to economic

rights.

risk and decision analysis~

of the greenhouse

of

and their willingness

for controlling

such as fossil

of fossil fuel burning

A complete

held by different future,

the If the

We are particularly

future environmental

incentives

threshold

and responses

degradation.

of the world towards an interactive

is

as we know them can be

to define an agreed-to

and to environmental

The study of economic

and social systems

We have stated that our concern

in such cases can ever be evaluated.

estimated,

limited

is

to a potential

to define the limits of stability of economic

socio-economic

o

in that

It seems quite likely that the major

rather than the ultimate

with very large perturbations,

o

states

problems

state.

with respect

o

relative

to be faced in future climatic

change of conditions~

future world

The essential difficulty here

of the unpredictable

Study of the adaptability

difficulties

possible

of far distant environmental

We

trying - currently

and understanding.

The

we have developed here and in other papers

is only a

beginning. o

Policy analysis of globally required

and represents

study of the C02/climate envisage

from expert physical

interdisciplinary

science analysts

program~

of greenhouse

of the effects of alternative

made by economists

though a gaming model

change problem has been developed

this as a strongly

evaluations

imposed trace gas emission control measures

a completely new effort~

remedial

and social and political

(ref.20).

with major

gas problems~ implementation

scientists.

is for

We

input and schemes

186

REFERENCES 1 2 3 4 5 6 7 8

9 i0 11 12 13 14 15 16 17 18 19 20

National Research Council, Changing Climate, National Academy Press~ Washington DC, USA, 1983. U.S. Department of Energy, State of the Art Report for the DOE CO 2 Program, Washington DC, USA, 1985. V. Ramanathan~ R.J. Cicerone, H.B. Singh & J.T. Kiehl~ J. Geo. Res. 90 (1985) 5547-5566pp. S. Seidel & D. Keyes, Can We Delay a Greenhouse Warming? Environmental Protection Agency, Washington DC, USA 1983. C. Marchetti~ Chem. Econ. & Eng. Rev. 11 (1979) 7-13pp. J.A. Laurmann, Energy i0 (1985) 761-775pp. J.A. Laurmann, in Proceedings of the Public Affairs Symposium on Greenhouse Problem Policy Options~ Univ. of Minnesota, USA, 1985. J. Hansen, A. Lacis~ D. Rind, G. Russell, P. Stone, I Fung 9 R. Ruedy & J. Lerner, in Climate Process and Climate Sensitivity, Amer. Geo. Union, Washington D.C. USA, (1984) 130-163. J. Woods, Nature 314 (1985) 578-579. J. A. Laurmann~ Policy Implications of Ocean Thermal Response Time in Man-made Climate Change Nature, to be published. J. A. Laurmann, in Carbon Dioxide: Current Views and Developments in Energy/Climate Research, Reidel~ Dordrecht~ Holland (1983), 415-460. J. A. Laurmann, in Interactions of Energy and Climate, Reidel, Dordrecht Holland (1980), 437-460. H. Raiffa, Decision Analysis, Introductory Lectures on Choices under Uncertainty, Addison-Wesley, Reading USA, 1970. R. C. Lind, Discounting for Time and Risk in Energy Policy, John Hopkins Univ. Press, Baltimore USA, 1982. C. F. Baes, S. E. Beall, D. W. Lee & G. Marland~ in Interactions of Energy and Climate~ Reidel, Dordrecht Holland (1980), 495-519. M. Steinberg & A. S. Albenese, in Interactions of Energy and Climate, Reidel, Dordrecht Holland (1980), 521-551. A. B. Lovins, L. H. Lovins, F. Krause & W. Bach, Least-cost Energy: Solving the Co 2 Problem~ Brick House, Andover USA, 1981. W. W Kellogg & R. Schware, Climate Change and Society~ Westview Press, Boulder USA, 1981. J. A. Laurmann, Climatic Change, 7(1985) 261-265. J. Ausubel, J. Lathrop, I. Stahl & J. Robinson, Carbon and Climate Gaming, IIASA WP-80-152, 1980.