Figure 2 shows estimated potential changes in average national crop yields for
the GISS, GFDL and UKMO 2 ; CO
climate change scenarios, allowing for
the direct effects of CO
on plant growth. Latitudinal differences are apparent in
all the scenarios. Higher latitude changes are less negative or even positive in
some cases, while lower latitude regions indicate more negative effects of climate
change on agricultural yields.
The GISS and GFDL climate change scenarios produced yield changes
ranging from ;30 to 930%. The GISS scenario is, in general, more detrimental
than the GFDL for crop yields in parts of Asia and South America, while GFDL
results in more negative yields in the USA and Africa and less positive results in
the former USSR. The UKMO climate change scenario, which has the greatest
warming (5.2 °C global surface air temperature increase) suggests yield declines
almost everywhere (up to 950% in Pakistan).
Effects on World Food Trade
Effects on food production. The future without climate change. Assuming no
effects of climate change on crop yields but that population growth and economic
growth are as stated above, world cereal production is estimated at 3286 million
tonnes (Mt) in 2060 compared with 1795 Mt in 1990. Cereal prices are estimated
at an index of 121 (1970 : 100). The number of people at risk of hunger is
estimated at about 640 million (cf. 530 million estimated in 1990).
Effects of climate change with internal adjustment in the model but without
adaptation. Under the estimated effects of climate change and atmospheric CO
on crop yields, world cereal production is estimated to decrease between 1 and
7% depending on the GCM climate scenario (Figure 3). Under the UKMO
scenario, global production is estimated to decrease by more than 7%, while
under the GISS scenario (which assumes lower temperature increases) cereal
production is estimated to decrease by just over 1%. The largest negative changes
occur in developing countries, averaging 99% to 911%. By contrast, in
developed countries production is estimated to increase under all but the UKMO
scenario (;11% to 93%). Thus existing disparities in crop production between
the developed and developing countries are estimated to grow.
Effects of climate change on production under different levels of adaptation. The
study tested the efficacy of two levels of adaptation: Level 1 implies little change
to existing agricultural systems reflecting farmer response to a changing climate,
whereas Level 2 implies a more substantial change to agricultural systems
possibly requiring resources beyond the farmer’s means. Level 2 adaptation
represents an optimistic assessment of world food agriculture’s response to
climate change conditions as predicted by the GCMs tested in this study. In each
case, the adaptations were tested as possible responses to the worst climate
change scenario (usually, but not always, the UKMO scenario). Changes in
economics or domestic agricultural policies were beyond the scope of this study;
the costs of adaptation and future water availability under the climate change
scenarios were also not considered.
Level 1 adaptation included:
M. Parry and M. Livermore
118
the GISS, GFDL and UKMO 2 ; CO
climate change scenarios, allowing for
the direct effects of CO
on plant growth. Latitudinal differences are apparent in
all the scenarios. Higher latitude changes are less negative or even positive in
some cases, while lower latitude regions indicate more negative effects of climate
change on agricultural yields.
The GISS and GFDL climate change scenarios produced yield changes
ranging from ;30 to 930%. The GISS scenario is, in general, more detrimental
than the GFDL for crop yields in parts of Asia and South America, while GFDL
results in more negative yields in the USA and Africa and less positive results in
the former USSR. The UKMO climate change scenario, which has the greatest
warming (5.2 °C global surface air temperature increase) suggests yield declines
almost everywhere (up to 950% in Pakistan).
Effects on World Food Trade
Effects on food production. The future without climate change. Assuming no
effects of climate change on crop yields but that population growth and economic
growth are as stated above, world cereal production is estimated at 3286 million
tonnes (Mt) in 2060 compared with 1795 Mt in 1990. Cereal prices are estimated
at an index of 121 (1970 : 100). The number of people at risk of hunger is
estimated at about 640 million (cf. 530 million estimated in 1990).
Effects of climate change with internal adjustment in the model but without
adaptation. Under the estimated effects of climate change and atmospheric CO
on crop yields, world cereal production is estimated to decrease between 1 and
7% depending on the GCM climate scenario (Figure 3). Under the UKMO
scenario, global production is estimated to decrease by more than 7%, while
under the GISS scenario (which assumes lower temperature increases) cereal
production is estimated to decrease by just over 1%. The largest negative changes
occur in developing countries, averaging 99% to 911%. By contrast, in
developed countries production is estimated to increase under all but the UKMO
scenario (;11% to 93%). Thus existing disparities in crop production between
the developed and developing countries are estimated to grow.
Effects of climate change on production under different levels of adaptation. The
study tested the efficacy of two levels of adaptation: Level 1 implies little change
to existing agricultural systems reflecting farmer response to a changing climate,
whereas Level 2 implies a more substantial change to agricultural systems
possibly requiring resources beyond the farmer’s means. Level 2 adaptation
represents an optimistic assessment of world food agriculture’s response to
climate change conditions as predicted by the GCMs tested in this study. In each
case, the adaptations were tested as possible responses to the worst climate
change scenario (usually, but not always, the UKMO scenario). Changes in
economics or domestic agricultural policies were beyond the scope of this study;
the costs of adaptation and future water availability under the climate change
scenarios were also not considered.
Level 1 adaptation included:
M. Parry and M. Livermore
118