Working
Paper
THE
EFFECT
OF
cmnc
VARIATIONS
ON
AGRICULTURAL
RISK
M.L.
Parry
T.R.
Carter
August
1984
WP-84-69
International Institute for Applied Systems Analysis
A-2361 Laxenburg, Austria
NOT
FOR
QUOTATION
WITHOUT
PERMlSSlON
OF
THE
AUTHOR
THE
EFFECT
OF
CLIMATIC
VAFUATIONS
ON
AGRICLKTURAL
RISK
M.L.
Parry
T.R.
Carter
August
1984
WP-84-69
Working
Papers
are interim reports on work of the International Institute
for Applied Systems Analysis and have received only limited review. Views
or opinions expressed herein do not necessarily represent those of the
lnstitute or of
its
National Member Organizations.
INTERNATIONAL INSTITUTE FOR APPLIED SYSTEMS
ANALYSIS
2361
Laxenburg, Austria
Over the past decade the international scientific community and even the
popular media have been paying increasing attention to long-range climate
change--the extent and timing of global warming, shifts in precipitation patterns,
ecological, economic, and even geo-political effects.
Considerable research attention should obviously be addressed to the pros-
pects for and implications of seminal climate change; such a development could
have historic consequences. But the global scale and the long-term nature of the
challenge, together
with the uncertainties still to be resolved, tend to make the
COz/climate issue, as it is usually presented,
a
residual claimant for the time and
attention of national and international policy communities. This
workng paper,
7he
Effect
of
Climatic
lh'ariations
on
AgricILltIL~al
Risk,
approaches the problem of
climate change from a different perspective in terms of both spatial and temporal
scales. It addresses "present day impacts from short-term climate variability".
And it examines, as a case in point, the shifts of climate-related risk level and agri-
cultural growth potential
for a single crop (oats) in a single locality (southern Scot-
land).
But, however interesting this may be as an exercise in analyzing the
climate-
risk issue under a particular set of conditions in a particular area, the authors have
a larger objective in mind: they wish to use their investigation of change of risk as
a building block for assessing the consequences for agriculture of long-term
(C02-
induced) climate change. Such
an
approach,
I
believe, will provide useful guidance
for those contemporary officials for whom a relatively remote, world-wide shift on
temperature and precipitation is too emphemeral to appear on already-crowded
policy agendas.
Professor Martin Parry and his associates at
IIASA are investigating the
impacts of short-term climatic variations and the likely long-term 'effects of
COz-
induced climatic changes on food output at the sensitive margins of production.
This work is part of a two-year effort and is expected to be completed. by December,
1985.
Dr. Chester
L.
Cooper
Special Advisor to the Director
Acting Head of the Environmental Program
The thesis of this paper is that impacts from climatic change can be evaluated
effectively as changes in the frequency of short-term, anomalous climatic events.
These can then be expressed as changes in the level of risk of impact from climatic
extremes. To evaluate this approach, the risk of crop failure resulting from low lev-
els of accumulated temperature is assessed for oats farming in southern Scotland.
Annual accumulated temperatures are calculated for the 323-year long tempera-
ture record compiled by
Manley for Central England. These are bridged across to
southern Scotland and, by calculating mean levels of risk for different elevations,
an average "risk surface" is constructed. I-in-10 and 1-in-50 frequencies of crop
failure are assumed to delineate
a
high-risk zone, which is mapped for the 323-year
period by constructing isopleths of these risk levels.
By
re-dravling the risk iso-
pleths for warm and cool 50-year periods, the geographical shift of the high-risk
zone is delineated. The conclusion is that relatively recent and apparently minor
climatic variations in the United Kingdom have in fact induced substantial spatial
cbmges in levels of agricultural risk.
h
advantage of expressing climatic change
as a change in agricultural risk, is that support programs for agriculture can be
re-tuned to accommodate acceptable frequencies of impact by adjusting support
levels to match new risk levels.
CONTENTS
1.
Introduction
2. Long-Term Variations in Growth Potential
2.1. Selection
,of the Parameter
2.2. Central England Accumulated Temperatures,
1659-1981
2.3. The Chronology of Accumulated Warmth
2.4. Derivation of Proxy Accumulated Temperatures for Southern Scotland
2.4.1.Bridging from Central England to Edinburgh
2.4.2.Bridging from Ebnburgh to Southern Scotland
3. The Frequency of Crop Failure
3.1. Method
3.2. Predicting the Location of Crop Failure
4.
A
Risk Surface of Crop Failure
5.
Delimiting High-Risk Areas
6.
Changes in the Frequency of Crop Failure
7.
Conclusions
References
-
vii
-
