Thesis on Climate Change and Its Impact on Agricultural fields

8/22/2019 Thesis on Climate Change and Its Impact on Agricultural fields

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INTRODUCTION

Most agronomists believe that agricultural production will be affected by

the severity and pace of climate change. If change is gradual, there may be

enough time for adjustment. Rapid climate change, however, could harm

agriculture in many countries, especially those that are already suffering

from poor soil and climate conditions, because there is less time for

optimum natural selection and adoption.

People in India, especially the poorest, are vulnerable to the impact

of climate change, because the nations economy is so closely tied to

nature resources .For example, more than 57% of works are engaged in

agriculture and allied sectors, areas through earn their living in coastal

areas though tourism or fishing. Most of Indians poorest people live in

rural areas, almost totally reliant on natural resources for their food,

shelter and incomes. The yare already experiencing the impact of climate

change, with few resources to cope.

INDIA AND AGRICULTURE

CONTEXT

Population : 1 billion +

GDP from Agriculture : 34 % (1994), 42 % (1980)

Area under Agriculture : 50 % (160 mha)

Population dependent on Agriculture: 70%

Average farm size: : 1 to5 ha

Indian Agriculture- Some Facts

Total Geographical Area - 328 million hectares

Net Area sown - 142 million hectares

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Gross Cropped Area 190.8 million hectares

Major Crop Production (1999-2000)

Rice 89.5 million tonnes

Wheat 75.6 million tonnes

Coarse Cereals 30.5 million tonnes

Pulses 13.4 million tonnes

Oilseeds 20.9 million tonnes

Sugarcane 29.9 million tonnes

Indian Agriculture- Some Facts

Contributes to 24% of GDP

Provides food to 1Billion people

Sustains 65% of the population : helps alleviate poverty

Produces 51 major Crops

Provides Raw Material to Industries

Contributes to 1/6th of the export earnings

One of the 12 Bio-diversity centers in the world with over 46,000

species of plants and 86,000 species of animals recorded

During the last decade, the Indian state of Uttar Pradesh has been

witness to many climatic changes. Eastern Uttar Pradesh has faced severe

floods, while Bundelkhand region has faced one of the warmest famines

of the last decade. Thus, the impact of climate change has adversely

affected agricultural production resulting in huge loss of paddy and corn

crops in eastern districts and regional crops in Bundelkhand.

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Climate change impeding agricultural production in India during

the last decade, the Indian state of Uttar Pradesh has been witness to many

climatic changes. Eastern Uttar Pradesh has faced severe floods, while

Bundelkhand region has faced one of the worst famines of the last decade.

Thus, the impact of climate change has adversely affected agricultural

production resulting in huge loss of paddy and corn crops in eastern

districts and regional crops in Bundelkhand. Climate-related disasters

have brought widespread misery and huge economic losses to Uttar

Pradesh, adversely affecting public health, food security, agriculture,

water resources and biodiversity in the state. Floods are the most common

annual occurrence in the state, affecting one or the other part of the state;the most affected being the districts of the eastern U.P. and terai region.

Agriculture in India is very much weather-dependent. It is ironic, then,

that a significant percentage of greenhouse-gas emissions come from

agriculture. Fossil-fuel intensive agriculture is contributing to the creation

of the unpredictable weather conditions which all farmers will need to

battle in the not so distant future. Scientists believe that the fluctuating

weather conditions in the state suggest that the state is reeling under

climatic chaos. For more than a decade now, the state has been

experiencing contrasting extreme weather conditions and agriculture has

been worst affected by these climatic changes. A little decrease in

temperatures can reduce the production of wheat crops, but help in the

growth of paddy. Such changes may often tilt the farmers towards

growing one crop at the expense of the other. This would lead to

imbalances in crop production. According to the 2001 census, 62.12

percent of the states total workers are engaged in agriculture. UP

contributes, on an average, 21 percent to the national production of food

grain. With an average annual food grain production of about 42.7 million

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tons and per capita production of 234 kg, U.P. ranks third highest among

major states, and is considered to be a food grain surplus state. The

growing water scarcity poses further problems of survival to people and

animals alike. Already there have been reports of cattle deaths due to

water scarcity in the district. In recent years, the water level has gone

down significantly. The ill effects of climate change can also be seen on

women farmers, especially poor women farmers because of their low

social and economic status. They also have lesser accessibility to

livelihood resources and land holdings. There is a serious danger of

climatic changes. (In the form of severe droughts, floods, intense rainfall,

and storms) undermining development programmes and millenniumdevelopment goals aimed at reducing poverty. Currently India is spending

2.5% of its total GDP on measures to control the adverse impact of

climatic change, which is a big amount for any developing nations. The

zeal of rapid industrialization, deforestation and willful consumption of

natural resources is likely to make the situation worse. Policy makers at

the state, regional and national level should take a serious view of the

economic, agricultural, health-related and environmental impacts of

climate changes.

Land Use, Land Cover Change, & Agriculture

Land use and land cover are linked to climate and other

environmental changes in complex ways, such as the exchange of

greenhouse gases between plants and soils and the atmosphere, the effects

of changes in land use and land cover on Earth's heat balance, and the

impacts of changing environmental conditions on terrestrial ecosystems

and biodiversity. Past land-cover changes are important to understanding

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past climate variability and change, and projections of future land cover

change are needed as input to models of future climate changes. Changes

in land use and land cover affect ecosystems, biodiversity, agricultural

productivity, and other goods and services of value to society. The

National Research Council carries out a variety of studies, workshops, and

meetings and publishes numerous reports on science-policy issues related

to environmental change, land use, land cover change, and agriculture

.Land Use, Land Cover Change, & Agriculture activities at the National

Academies. Agriculture effects climate change & climate change

effects agriculture The greenhouse effect.

The earth is surrounded by an atmosphere through which solar

radiation is received. The atmosphere is not static but contains air, in

constant motion, being heated, cooled and moved, water being added and

removed along with smoke and dust. Only a tiny proportion of the sun's

energy reaches earth and some of this is reflected back into space (from

clouds etc.). When the radiant energy reaches the land surface, most of it

is absorbed, being used to heat the earth, evaporate water and to power

photosynthetic processes. The earth also radiates energy but, because it is

less hot than the sun, this is of a longer wavelength and is absorbed by the

atmosphere. The Earths atmosphere, thus acts like the glass of a green

house, hence the 'greenhouse effect'. The greenhouse gases (dealt with in

subject 3) are those that absorb the Earths radiation and thus contribute to

the greenhouse effect, but water is also a major absorber of energy. Where

there is an increase in the concentration of greenhouse gases (as with CO2

due to the burning of fossil fuels) this result in an enhanced greenhouse

effect - which is of concern as it could lead to climate change (i.e. global

warming).

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Global Warming

Global temperatures have risen by over 0.7oC in the last 100 years

and eleven of the last twelve years (1995-2006) are the warmest on

record. In the UK in 1990s were very warm about 0.6oC warmer than the

mean 1961 - 1990 temperature. Warm winters have reduced the number of

frosts, and the warmer summers have included record hot spells and high

sunshine totals.

How will climate change effect agriculture

Soil processes

The potential for soils to support agriculture and distribution of land use

will be influenced by changes in soil water balance:

Increase in soil water deficits i.e. dry soils become drier, therefore

increased need for irrigation but: Could improve soil workability in

wetter regions and diminish poaching and erosion risk Crops

The range of current crops will move northwardNew crop varieties may need to be selectedHorticultural crops are more susceptible to changing conditions than

arable cropsField vegetables will be particularly affected by temperature changesPhaselous bean, onion and sweetcorn are most likely to benefit

commercially from higher temperaturesWater deficits will directly affect fruit and vegetable production

The effect of increased temperature and CO2 levels on arable crops

will be broadly neutral:

How will climate change effect cropping in tropical and arid Countries?

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Grasslands and livestock

There is unlikely to be a significant change in suitability of livestock for

UK systemsPigs and poultry could be exposed to higher incidences of heat stress,

thus influencing productivityIncrease in disease transmission by faster growth rates of pathogens in

the environment and more efficient and abundant vectors (such as

insects)Consequences for food quality and storage

Weeds, pests and diseases:

Weeds evolve rapidly to overcome control measures, short lived weeds

and those that spread vegetatively (creeping buttercup, couch etc) evolve

at the greatest rate:

Grassland and arable weeds could become more tolerant to control

measures

Rate of evolution will increase in hotter, drier conditions and in 'extreme

years', could lead to some types of herbicide tolerance becoming more

commonPossible increase in the range of many native pests, and species that at

present are not economically important may become soSurveillance and eradication processes for other significant pests, such

as the Colarado beetle will become increasingly important

Predicted effects of climate change on agriculture over the next 50 years

Climatic

element

Expected changes

by 2050's

Confidence

in

Effects on agriculture

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prediction

CO2

Increase from 360

ppm to 450 - 600

ppm (2005 levels

now at 379 ppm)

Very high

Good for crops: increased

photosynthesis; reduced

water use

Sea level rise

Rise by 10 -15 cm

Increased in south

and offset in north

by natural

subsistence/rebound

Very high

Loss of land, coastal

erosion, flooding,

salinisation of groundwater

Temperature

Rise by 1-2oC.

Winters warming

more than summers.

Increased frequency

of heat waves

High

Faster, shorter, earlier

growing seasons, range

moving north and to higher

altitudes, heat stress risk,

increased

evapotranspiration

PrecipitationSeasonal changes by

10%Low

Impacts on drought risk'

soil workability, water

logging irrigation supply,

transpiration

Storminess

Increased wind

speeds, especially in

north. More intense

rainfall events.

Very low

Lodging, soil erosion,

reduced infiltration of

rainfall

Variability Increases across

most climatic

variables.

Predictions uncertain

Very low Changing risk of damaging

events (heat waves, frost,

droughts floods) which

effect crops and timing of

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farm operations

Source: Climate change and Agriculture, MAFF (2000)

Current projections, from the 4th Assessment report by the

Intergovernmental Panel on Climate Change (IPCC) published in 2007,

suggest that global temperatures will rise between 1.8oC and 4.0oC (best

estimate) by 2100 depending on emissions of greenhouse gases and that

global sea levels are likely to rise from anywhere between 180mm and

590mm. For further details go to the IPCC website.Pause for

thought......Should farmers take into account predicted climate changes

when 'planning for the long term future' of their businesses? he

Implications of Climate Change for Crop Yields, Global Food Supply and

Risk of Hunger The potential effects of climate change on crop yield, food

production and risk of hunger. There are two global studies of crop yield

responses and several additional estimates of production that are based on

the first of these. The studies cover three broad type of analysis:

1) Effects under climate change but with underlying socio-economic

characteristics largely unspecified,

2) Effects under both changes in climate and with varying development

pathways assumed to affect underlying socio-economics, and

3) Effects under different policies of stablisation of greenhouse gases.

There are some conclusions common to all studies: that climate change

will generally reduce production potential and increase risk of hunger, and

that Africa is the most adversely affected region. An additionally

important initial conclusion is that pathways of sustainable economic

development have a marked effect in reducing the adverse effects on

climate change.

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The early 1990s that have considered the effects of climate change

on crop yield potential, cereal production, food prices and the implications

for changes in the number of hungry people. The IPCC has recently

concluded that, while there is extensive potential to adapt to small

amounts of warming, and that the next few decades might even bring

benefits to higher latitudes through longer growing seasons, at lower

latitudes even small amounts of warming would tend to decrease yields

and, beyond about two degrees of warming would decrease yields in

almost all parts of the world 1. This regional unevenness of effect climate

change on agriculture around the world has very great implications for

food security, especially when (even without the challenge of climatechange) almost 800 million people in the developing world are estimated

to be to experiencing some form of shortage in food supply 2. Where

crops are grown near their maximum temperature tolerance and where

dryland, non-irrigated agriculture predominates, the challenge of climate

change could be overwhelming, especially on the livelihoods of

subsistence farmers and pastoral people, who are weakly coupled to

markets.

The paper is divided into four parts, reflecting the four main sets of

studies that have been published: 1) Studies in the early 1990s using

point-based crop growth models with what are now termed low

resolution models of climate, 2) later studies which used higher

resolution models, 3) Ricardian and other economic approaches that used

the yield estimates from the foregoing to develop estimates of production,

and 4) studies which have incorporated more spatially resolute analyses of

altered yield potential based on GIS systems rather than point-based

modelling.

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Effects on yields and production

The results show that climate change scenarios which exclude the

direct physiological effects of CO2 predict decreases in simulated yields

in many cases, while the direct effects of increasing atmospheric CO2

mitigate the negative effects primarily in mid and high latitudes. The

differences between countries in yield responses to climate change are

related to differences in current growing conditions. At low latitudes crops

are grown nearer the limits of temperature tolerance and global warming

may subject them to higher stress. In many mid and high latitude areas,

increasing temperatures may benefit crops otherwise limited by coldtemperatures and short growing seasons in the present climate.

Under the estimated effects of climate change and atmospheric CO2

on crop yields, world cereal production is estimated to decrease between 1

and 7% depending on the GCM climate scenario. The largest negative

changes occur in developing countries, averaging 9% to 4, 11%. By

contrast, in developed countries production is estimated to increase under

all but the UKMO scenario (+11% to 3%). Thus existing disparities in

crop production between the developed and developing countries are

estimated to grow. Decreases in production are estimated by the BLS to

lead to increase in prices (by 25 to 150%) and increases in hunger (by 10

to 60 %) The study tested the efficacy of two levels of adaptation: Level

1 adaptation included: shifts in planting date that do not imply major

changes in the crop calendar; additional application of irrigation water to

crops already under irrigation; changes in crop variety to currently

available varieties better adapted to the projected climate. Level 2

adaptation included: large shifts in planting date; increased fertiliser

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application; development of new varieties; installation of irrigation

systems.

Effect under different levels of adaptation

Level 1 adaptation largely offset the negative climate change

induced effects in developed countries, improving their comparative

advantage in world markets. In these regions cereal production increases

by 4% to 14% over the reference case. However, developing countries are

estimated to benefit little from adaptation (-9% to 12%). Averaged

global production is altered by between 0% and 5% from the reference

case. As a consequence, world cereal prices are estimated to increase by10-100% and the number of people at risk from hunger by c 5-50% . This

indicates that Level 1 adaptations would have relatively little influence on

reducing the global effects of climate change. More extensive adaptation

(Level 2) reduces impacts by a third and in some cases virtually eliminates

them. However, the decrease in the comparative advantage of developing

countries under these scenarios leads to decreased areas planted to cereals

in these areas. Cereal production in developing countries still decreases by

around 5%. Globally, however, cereal prices increase by only 5 to 35%,

and the number of people at risk from hunger is altered by between 2%

and +20% from the reference case (Figure 3). This suggests that Level 2

adaptations are required to mitigate 5 the negative effects of climate

change but that these still do not eliminate them in developing countries.

Net imports of cereals into developing countries will increase under all

scenarios. The change in cereal imports is largely determined by the size

of the assumed yield changes, the change in relative productivity in

developed and developing regions, the change in world market prices and

changes in incomes of developing countries. Under the GISS climate

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scenario productivity is depressed largely in favour of developed

countries, resulting in pronounced increases of net cereal imports into

developing countries. Under the UKMO scenario large cereal price

increases limit the increase of exports to developing countries.

Consequently, despite its beneficial impact for developed countries, the

Adaptation Level 1 scenarios show only small improvements for

developing countries as compared to the corresponding impacts without

such adaptation.

Effects of climate change

Changes in cereal production, cereal prices, and people at risk of

hunger estimated for the HadCM2 climate change scenarios (with the

direct CO2 effects taken into account) show that world is generally able to

feed itself in the next millennium. Only a small detrimental effect is

observed on cereal production, manifested as a shortfall on the reference

production level of around 100mmt (-2.1%) by the 2080s (+/-10mmt

depending on which HadCM2 climate simulation is selected). In

comparison, HadCM3 produces a greater disparity between the reference

and climate change scenario - a reduction of more than 160mmt (about

-4%) by the 2080s . Reduced production leads to increases in prices.

Under the HadCM2 scenarios cereal prices increase by as much as 17%

(+/- 4.5%) by the 2080s (Figure 4). The greater negative impacts on yields

projected under HadCM3 are carried through the economic system with

prices estimated to increase by about 45% by the 2080s. In turn these

production and price changes are likely to affect the number of people

with insufficient resources to purchase adequate amounts of food.

Estimations based upon dynamic simulations by the BLS show that the

number of people at risk of hunger increases, resulting in an estimated

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additional 90 million people in this condition due to climate change

(above the reference case of ~250 million) by the 2080s (Figure 4). The

HadCM3 results are again more extreme, falling outside the HadCM2

range with an estimated 125+ million additional people at risk of hunger

by the 2080s. All BLS experiments allow the world food system to

respond to climate-induced supply shortfalls of cereals and higher

commodity prices through increases in production factors (cultivated land,

labour, and capital) and inputs such as fertiliser.

Initial analyses using low resolution climate models

The first model-based studies of effects on global food supply were

published in the early 1990s. The general conclusions of that work stillhold today: that climate change is likely to reduce global food potential

and that risk of hunger will increase in the most marginalised economies

3. In these studies there were two main tasks: Firstly, the estimation of

potential changes in crop yield using crop models and a decision support

system developed by the US Agency for International Developments

International Benchmark Sites Network for Agrotechnology Transfer

(IBSNAT) 4,5. The crops modelled were wheat, rice, maize and soybean,

accounting for more than 85% of the worlds traded grains and legumes.

Secondly, the estimation of food production, prices and the number of

people at risk of hunger by using estimated yield changes in a world food

trade model, The Basic Linked System (BLS) developed at the

International Institute for Applied Systems Analysis (IIASA) 6. The

scenarios for these early studies were created by changing the observed

data on current climate (1951-80) according to doubled CO2 simulations

of three general circulation models (GCMs). The 2 as to understand the

nature of these complex interactions, and how they affect people at risk of

hunger in the GCMs used were those from the Goddard Institute for Space

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Studies (GISS) 7,8, Geophysical Fluid Dynamics Laboratory (GFDL)9

and the United Kingdom Meteorological Office (UKMO) 10. The

IBSNAT crop models were used to estimate how climate change and

increasing levels of carbon dioxide may alter yields of work crops at 112

sites in 18 countries representing both major production areas and

vulnerable regions at low, mid and high latitudes 11. The IBSNAT models

employ simplified functions to predict the growth of crops as influenced

by the major factors that affect yields, e.g. genetics, climate (daily solar

radiation, maximum and minimum temperatures and precipitation), soils

and management practices. Models used were for wheat 12, 13, maize 14,

15, paddy and upland rice 16 and soybean 17. The analyses included theeffects of enhanced ambient C02 levels on crop growth both through

altered water-use efficiency and rates of photosynthesis 19,20

21,22,23,24,25, . but the crop models did not simulate effects of altered

climate on weeds and insect pests. Regional yield estimates were derived

from the modelled site information, assuming the current mix of rainfed

and irrigated production, the current crop varieties, nitrogen management

and soils. Although the number of sites was limited (112 in all) it was

argued that these related to regions that account for about 70% of the

worlds grain production 26, and thus could enable credible conclusions

concerning world production to be drawn. The altered yield data was input

to a dynamic model of the world food system (the Basic Linked System)

in order to assess the possible impacts on the future levels of food

production, food prices and the number of people at risk from hunger27. It

consists of 20 national and/or regional models that cover around 80% of

the world food trade system. The remaining 20% is covered by 14

regional models for the countries that have broadly similar attributes (e.g.

African oil exporting countries, Latin American high income exporting

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countries, Asian low income countries). The grouping is based on country

characteristics such as geographical location, income per capita and the

countrys position with regard to net food trade 3,27. The BLS does not

incorporate any climate relationships per se. Effects of changes in climate

were introduced to the model as changes in average national or regional

yield per commodity as estimated above. Ten commodities are 3 included

in the model: Wheat, rice, coarse grains (e.g. maize, millet, sorghum, and

barley), bovine and ovine meat, dairy products, other animal products,

protein feeds, other food, non-food agriculture and non-agriculture. In this

context, however, consideration is limited to the major grain food crops.

As in most studies of impacts of climate change, the modelled yields werefirst estimated for a baseline scenario (a trended future case assuming no

climate change). This involved projection of the agricultural system to the

year 2060 with projected yields and a projected political and economic

context of the world food trade. These projections assumed: a world

population of 10.2 billion by 2060 (the UN median estimate); 50% trade

liberalisation in agriculture introduced gradually by 2020; moderate

economic growth (ranging from 3.0% per year in 1980-2000 to 1.1% per

year in 2040-2060); crop yield for world total, developing and developed

countries increasing annually by 0.7%, 0.9% and 0.6%, respectively.

Three further scenarios were introduced: those which assumed differing

levels of adaptation, which assumed varying amounts of future economic

and population growth , and assumed full rather than partial trade

liberalisation,

Analyses for different socio-economic scenarios

More recently, the projected effects of climate change on global

food supply have been considered under different pathways of future

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socio-economic development, expressed in terms of population and

income level, which have been characterised by the Special Report on

Emissions Scenarios (SRES) of the Intergovernmental Panel on Climate

Change (IPCC). Differing trajectories of population growth and economic

development will affect the level of future climate change and,

simultaneously, the responses of agriculture to changing climate

conditions at regional and global scales. The goal of the study wcoming

decades Consistent climate change scenarios have been taken from SRES-

driven experiments conducted using the UK Hadley Centres third

generation coupled atmosphere-ocean global climate model (HadCM3)32.

The use of a transient AOGCM (HadCM3) allows not only the effect ofthe magnitude of climate change on food production to be assessed but

also the effects of rate of change. The structure and research methods

remain the same as in previous work 3,31,33. Population levels for each

SRES scenario for given timelines were taken from the CIESIN

database33. These levels, together with income level, drive estimated

future demand for cereals in the BLS. The BLS was first run for a

reference case (i.e. assuming no climate change) for each SRES pathway

(A1, A2, B1 and B2) where fluctuations in productivity and prices are

solely the outcome of the socio-economic development pathway. The

model was then re-run with estimated changes in regional cereal yields

due to climate change entered into the model altering regional agricultural

productivity, global food prices and the level of exposure of the global

population to the risk of hunger.

Effects on yields

Each HadCM3 climate change scenario produced by the four

different SRES emissions scenarios instigates a different development

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path for global crop yields. These paths do not diverge, however, until

mid-century. By the 2020s, small changes in cereal yield are evident in all

scenarios, but these fluctuations are within historical variations. Although

there are differences in the mean impacts of the SRES scenarios, the range

of the spatial variability projected is similar. Generally, the SRES

scenarios result in crop yield decreases in developing countries and yield

increases in developed countries (Table 1)33. The A1FI scenario, as

expected with its large increase in global temperatures, exhibits the

greatest decreases both regionally and globally in yields, especially by the

2080s. Decreases are especially significant in Africa and parts of Asia

with expected losses up to 30 percent. In these locations, effects oftemperature and precipitation changes on crop yields are beyond the

inflection point of the beneficial direct effects of CO2. In North America,

South East South America, and Australia, the effects of CO2 on the crops

partially compensate for the stress that the A1FI climate conditions

impose on the crops and result in small yield increases. In contrast to the

A1FI scenario, the coolest climate change scenario (B1) results in smaller

cereal yield decreases.

The contrast between the yield change in developed and developing

countries is largest under the A2 scenarios. Under the A2 scenarios, crop

yields in developed countries increase as a result of moderate temperature

increases, and the direct effects of the high concentration of CO2. In

contrast, crop yields decrease in developing countries as a result of

regional decreases in precipitation and temperature increases. The results

highlight the complex regional patterns of projected climate variables,

CO2 effects, and agricultural systems that affect crop production under

the different SRES futures.

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Effects on cereal production, cereal prices, and risk of hunger

The reference case - the future without climate change. The BLS

projects year-on-year increases in production, assuming no change in

climate, as indicated. The differences between the SRES scenarios reflects

different assumptions about population (and resulting demand) and

income levels (and resulting consumption). While more cereals are being

produced, the increase in demand ensures that global cereal prices also

rise, most notably under the A2 world where increases of more than 160%

(compared to current day market prices) are to be expected by the 2080s.

In contrast, in the A1 and B1 worlds, after a moderate increase of between

30 and 70% by the 2050s, a decline in cereal prices towards the end of thiscentury is projected in accordance with the expected decline in global

populations. The difference between the A1 and B1 worlds which share

identical population growth projections is primarily due to the higher level

of economic development in the A1 world which allows higher market

prices. The result is that A1, B1 and B2 see a decline in the global number

of people at risk of hunger throughout this century as the pressure caused

by increases in cereal prices is offset by an increase in global purchasing

power. In contrast in the A2 world, where inequality of income remains

great, the number is largely unaltered, at around 800 million people.

The future with climate change. The impact of climate change on

global cereal production under the seven SRES scenarios. The changes are

shown as reductions in millions of metric tonnes from the reference case

(the future without climate change). Substantial reductions in production

are estimated assuming no beneficial effects of CO2: About 5 per cent

reductions for B1 and B2 by the 2080s, and 10 per cent for A1 and A2.

The difference can be explained by greater temperature increases in the

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latter. However, when CO2 effects are assumed to be fully operative, the

levels of reduction diminish by about two-thirds, and the differences

between the scenarios are much less clear. It appears that smaller

fertilization effects under B1 and B2 lead to greater reductions than A1

and A2. Much thus depends on how these CO2 effects play out in reality.

At present we do not know, suffice to say that the effects will fall

somewhere between the with CO2 levels and the without CO2 levels.

As would be expected, an inverse pattern in the estimated change in

global cereal prices tends to occur with large price increases (under no

CO2) for the A1 and A2 scenarios, more than a three-fold increase over

the reference case by the 2080s, and less than half this increase under B1and B2. Under both scenarios there is little sign of any effect until after c.

2020.

The measure risk of hunger is based on the number of people whose

incomes allow them to purchase sufficient quantities of cereals31, and

therefore depends on the price of cereals and the number of people at

given levels of income. The number of additional millions at risk of

hunger due to climate change (that is, compared with the reference case)

is shown in Figure 10. Assuming no CO2 effects, the number at risk is

very high under A2 (approaching double the reference case) partly

because of higher temperatures and reduced yields but primarily because

there are many more poor people in the A2 world which has a global

population of 15 billion (c.f. 7 billion in A1FI). And the number of people

at risk is much lower in the B1 and B2 worlds which are characterised

generally by fewer poor people.

Analyses of production potential using Ricardian methods

Based on broadly the same set of the crop yield estimates 34 a

recent study has used a series of Ricardian country and regional models to

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estimate altered food production due to climate change 35. The assumed

climate scenarios are the same as previously discussed, but the economic

models allow for land-use changes that would accompany shifts in land

values due to alterations in comparative advantage between crops, giving

a more realistic indication of the potential response. The results differ only

in degree from those of the previous studies. Global agricultural output is

estimated to decrease by 16 per cent assuming no carbon fertilisation, and

by 3 per cent with full carbon fertilisation . The regional pattern shows

quite strong adverse effects on yield in tropical areas, especially Africa,

the Middle East and the south Asia.

Analyses based on changes in agro-ecological zones.

A very different approach from point-based crop-growth modelling

is the study of how zones of crop suitability may shift location in response

to changes of climate. When combined with modelling of the length of

crop growing season, either due to changes in moisture or heat

availability, this method enables evaluation of both changes in yield at any

given place in combination with changes in extent of suitability 36. These

broadly mirror the estimates on the point-based modelling of a decade

arlier, showing decreases in cereal output in developing countries and

increases in developed countries. Increases in potential occur in northern

parts of North America and Europe, in contrast to decreases in Africa and

South America. These geographical differences are reflected in the

additional numbers estimated to be at risk of undernourishment due to

climate, which for 2080 range from 40 (for the smallest amount of

warming, B2) to 170 million (for the highest, A1FI) (Figure 14).

The two different analyses ( crop model and crop zone suitability)

give broadly similar estimates of global numbers additional at risk from

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hunger or under-nourishment. While both use the BLS the two approaches

adopt quite different methods in modelling altered crop yields; and this

gives greater confidence to estimates of ultimate effects on hunger.

Comparing the range of analyses

Other studies have either used a macro-economic approach, or yield

estimates from previous crop modelling as inputs to different economic

models. One 37 uses six broad land classes around the world and analyses

the change in extent of these due to altered moisture and temperature, the

yield results from which are very similar to the analyses from crop

models. But the economic assumptions in the approach, especially theland-use changes, eliminate three-quarters of the climate-induced

reductions in production, at least until high levels of warming (above 3

deg C) start to reduce land suitability markedly. A summary of the

different approaches by the IPCC 38 indicates that all conclude a decrease

in output and consequent increase in prices, but vary in their conclusion

regarding when (along a pathway of increasing global temperature) this

decrease will occur. The crop modelling and agro-ecological analyses

conclude that prices will rise with even small amounts of warming ( 1 to 2

deg C), while the other analyses suggest that they will first decrease (due

to increased potential with extended growing seasons at higher latitudes)

before decreasing when temperature increases exceed 2 or 3 deg C . This

point of inflection from a positive to a negative effect on global food

output, and whether it occurs at 1 or 2 or 3 degrees C increase in global

temperature, is central to the current debate as to whether global warming

may, for the first few decades, have a beneficial effect. However, as we

have seen, such a point of inflection is dependent on the very uncertain

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mix of the positive effects from higher CO2 and the negative effective

from higher temperature.

Reducing impacts by stabilising CO2 concentrations at lower levels

The final section of this paper explores the implications of the

stabilisation of CO2 concentrations at defined levels39. These

stabilisation scenarios are among the set defined by the Intergovernmental

Panel on Climate Change 40.

Scenarios

Two stabilisation scenarios (stabilising at CO2 concentrations of 550ppmv and 750 ppmv) are considered, and compared with the IS92a

unmitigated emissions scenario41. There is little difference in

concentrations between the two scenariosup to the 2020s, but thereafter

they begin to diverge. The S750 scenario stabilises CO2 concentrations by

2250, whilst the S550 scenario assumes stabilisation occurs by 2150.

Achieving stabilisation at 750 ppmv and 550 ppmv, under the pathways

assumed here, requires cuts in annual CO2 emissions of around 13% and

30% respectively by 2025, relative to the 2025 emissions assumed under

IS92a. We interpret these stabilisation scenarios as representing actual

CO2 concentrations for the purposes of crop and vegetation modelling

(e.g. actual CO2 concentration reaches 750 ppmv by 2250), because there

are no accepted stabilisation scenarios for the other radiatively-significant

trace gases. We therefore assume that all other greenhouse gas

concentrations remain constant at 1990 values.

Effects on yield potential

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The estimated changes in national potential grain yield by the

2080s, assuming no changes in crop cultivars, under the three emissions

scenarios39. Under unmitigated emissions, positive changes in mid and

high latitudes are overshadowed by reductions in yield in the lower

latitudes. These reductions are particularly substantial in Africa and the

Indian subcontinent. However, many of the mapped changes in yield are

small and indistinguishable from the effects of natural climate variability.

Stabilisation at 550 ppmv produces far fewer reductions in yield, although

there would still be reductions in the Indian subcontinent, most of the

Pacific Islands, central America and the majority of African nations.

Stabilisation at 750 ppmv to a large extent produces intermediate changes.However, there are some interesting anomalies. Significant increases in

yields are seen in the mid-latitudes of both hemispheres under S750 which

are not replicated under S550.

The Impact of Climate Change on Agriculture

Climate change would strongly affect agriculture, but scientists still

dont know exactly how.

Most agricultural impacts studies are based on the results of general

circulation models (GCMs). These climate models indicate that rising

levels of greenhouse gases are likely to increase the global average

surface temperature by 1.5-4.5 C over the next 100 years, raise sea-levels

(thus inundating farmland and making coastal groundwater saltier),

amplify extreme weather events such as storms and hot spells, shift

climate zones poleward, and reduce soil moisture. Impacts studies

consider how these general trends would affect agricultural production in

specific regions. To date, most studies have assumed that agricultural

technology and management will not improve and adapt. New studies are

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becoming increasingly sophisticated, however, and "adjustments

experiments" now incorporate assumptions about the human response to

climate change.

Increased concentrations of CO2 may boost crop productivity. In

principle, higher levels of CO2 should stimulate photosynthesis in certain

plants; a doubling of CO2 may increase photosynthesis rates by as much

as 30-100%. Laboratory experiments confirm that when plants absorb

more carbon they grow bigger and more quickly. This is particularly true

for C3 plants (so called because the product of their first biochemical

reactions during photosynthesis has three carbon atoms). Increased carbondioxide tends to suppress photo-respiration in these plants, making them

more water-efficient. C3 plants include such major mid-latitude food

staples as wheat, rice, and soya bean. The response of C4 plants, on the

other hand, would not be as dramatic (although at current CO2 levels these

plants photosynthesize more efficiently than do C3 plants). C4 plants

include such low-latitude crops as maize, sorghum, sugar-cane, and millet,

plus many pastures and forage grasses.

Climate and agricultural zones would tend to shift towards the

poles. Because average temperatures are expected to increase more near

the poles than near the equator, the shift in climate zones will be more

pronounced in the higher latitudes. In the mid-latitude regions (45 to 60

latitude), the shift is expected to be about 200-300 kilometers for every

degree Celsius of warming. Since todays latitudinal climate belts are each

optimal for particular crops, such shifts could have a powerful impact on

agricultural and livestock production. Crops for which temperature is the

limiting factor may experience longer growing seasons.

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While some species would benefit from higher temperatures, others

might not. A warmer climate might, for example, interfere with

germination or with other key stages in their life cycle. It might also

reduce soil moisture; evaporation rates increase in mid-latitudes by about

5% for each 10C rise in average annual temperature. Another potentially

limiting factor is that soil types in a new climate zone may be unable to

support intensive agriculture as practiced today in the main producer

countries. For example, even if sub-Arctic Canada experiences climatic

conditions similar to those now existing in the countrys southern grain-

producing regions, its poor soil may be unable to sustain crop growth.

Mid-latitude yields may be reduced by 10-30% due to increased

summer dryness. Climate models suggest that todays leading grain-

producing areas - in Asia and Africa may experience more frequent

droughts and heat waves by the year 2030. Extended periods of extreme

weather conditions would destroy certain crops, negating completely the

potential for greater productivity through "CO2 fertilization". The

poleward edges of the mid-latitude agricultural zones - northern Canada,

Scandinavia, Russia, and Japan in the northern hemisphere, and southern

Chile and Argentina in the southern one - may benefit from the combined

effects of higher temperatures and CO2 fertilization. But the problems of

rugged terrain and poor soil suggest that this would not be enough to

compensate for reduced yields in the more productive areas.

The impact on yields of low-latitude crops is more difficult to

predict. While scientists are relatively confident that climate change will

lead to higher temperatures, they are less sure of how it will affect

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precipitation - the key constraint on low-latitude and tropical agriculture.

Climate models do suggest, however, that the inter-tropical convergence

zones may migrate poleward, bringing the monsoon rains with them. The

greatest risks for low-latitude countries, then, are that reduced rainfall and

soil moisture will damage crops in semi-arid regions, and that additional

heat stress will damage crops and especially livestock in humid tropical

regions.

The impact on net global agricultural productivity is also difficult to

assess. Higher yields in some areas may compensate for decreases in

others - but again they may not, particularly if todays major foodexporters suffer serious losses. In addition, it is difficult to forecast to

what extent farmers and governments will be able to adopt new

techniques and management approaches to compensate for the negative

impacts of climate change. It is also hard to predict how relationships

between crops and pests will evolve.

Adaptation

A wide variety of adaptive actions may be taken to lessen or

overcome adverse effects of climate change on agriculture. At the level of

farms, adjustments may include the introduction of later- maturing crop

varieties or species, switching cropping sequences, sowing earlier,

adjusting timing of field operations, conserving soil moisture through

appropriate tillage methods, and improving irrigation efficiency. Some

options such as switching crop varieties may be inexpensive while others,

such as introducing irrigation (especially high-efficiency, water-

conserving technologies), involve major investments. Economic

adjustments include shifts in regional production centers and adjustments

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of capital, labor, and land allocations. For example, trade adjustments

should help to shift commodity production to regions where comparative

advantage improves; in areas where comparative advantage declines,

labor and capital may move out of agriculture into more productive

sectors. Studies combining biophysical and economic impacts show that,

in general, market adjustments can indeed moderate the impacts of

reduced yields. A major adaptive response will be the breeding of heat-

and drought-resistant crop varieties by utilizing genetic resources that may

be better adapted to new climatic and atmospheric conditions. Collections

of such genetic resources are maintained in germ-plasm banks; these may

be screened to find sources of resistance to changing diseases and insects,as well as tolerances to heat and water stress and better compatibility to

new agricultural technologies. Crop varieties with a higher harvest index

(the fraction of total plant matter that is marketable) will help to keep

irrigated production efficient under conditions of reduced water supplies

or enhanced demands. Genetic manipulation may also help to exploit the

beneficial effects of CO2 enhancement on crop growth and water use.

Agriculture may decline due to climate change

The note has listed several ways by which these harmful emissions from the

agriculture sector can be reduced. These include better management of water and

fertilizers in the paddy fields and changes in the diet of livestock herds. Such

measures will cut down generation of both nitrous oxide and methane.

Besides, changes in land use patterns by expanding the area under agro-forestryand bio-fuel plantations could also mitigate GHG emissions. But these measures

may, however, lower land availability for food crops.

EFFECT OF CLIMAT CHANGE ON RURAL INDIA

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The study indicates that there will be substantial reduction in water

availability in large parts of north India as roughly 80 percent of water resource

needs are met primarily by Himalayas snow-pack melt during the dry summer

months. With retreating glaciers in the Himalayas and subsequent loss of fossil

water supply to the region is likely to be affected seriously. Global warming is one

of the important consequences of climate change and this will adversely affect

agriculture and rural life, A study c0ndycted at the India Institute of Technology,

Madras, indicates that a major aspect of climate change is sea-level rise and India

is vulnerable to rising sea levels due to a variety of reasons. India has the longest

coastline; India has the low-elevation coastal zones in India will be affected. The

report also suggests that global warming will affect the monsoon patterns in India,causing a significant damage to the health of Indias agricultural sector, which

plays a dominant role in the countrys economy. This report is prepared

independently and the study is based on the existing data provided by Inter-

governmental panel on Climate Change (IPCC), a global body that evaluates the

risk of climate change caused by human activity.

The study further indicates that there will be substantial reduction in water

availability in large parts of north India as roughly 80 per cent of whose water

resource needs are met primarily by Himalayan snow-pack melt during the dry

summer months. With retreating glaciers in the Himalayas and subsequent loss of

fossil water, the water supply to the region is likely to be affected seriously.

Himalayan glaciers and other global ice sheets have contributed more to the global

sea level over the past 80 years than was previously estimated. Similarly, a study

commissioned by Greenpeace India, on climate change notes that rising sea levels

could force about 50 million from Indias densely populated coastal regions to

migrate to interior towns and cities. His may generate severe tensions urban

resources. Climate change is likely to hit India hard in the coming decades. The

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Impact could increased water Scarcity, decreased crop yields, increased risk of

disease, and flooding of coastal areas. Climate change as a result of global a

warming will significantly impact on conditions of food supply and food security.

Since the 1960s,90 per cent of the excess heat due to higher greenhouse gas levels

has gone into the Oceans,7 per cent into warming the atmosphere does not warm

in the ext few year ,that is no reason for comfort so long as the strong warming

trend on the Oceans continues. The Oceans are crucial because they store so much

heat .It takes more than 1000 times more energy to heat a cubic meter of water by

1 degree0 C as it does the same volume of air .Globally, this means that if the

oceans transfer just a tiny fraction of their heat energy to the lower temperature

from year to year is due to heat sloshing back and forth between the oceans andatmosphere, rather tan any overall loss or gain of heat by the entire plant. The state

of the sea surface determines both air temperatures and rainfall. Solar radiation,

temperature, and precipitation are the main drivers of crop growth; therefore

agriculture has always been highly dependent on climate patterns and variations.

Overall, climate change could result in a variety of impacts on agriculture

.Changes in production patterns will occur due to higher temperatures and

changing precipitation patterns.

Meaning of climate change

Climate change refers to statistically significant variation in either the mean

state of the climate or in its variability, persisting for an extended period (typically

decades or longer). Climate change may be due to natural internal processes or

external forcing or to persistent anthropogenic change in the composition of the

atmosphere or in land use. The amount and speed of future climate change will

ultimately depend on:

*Whether greenhouse gases and aerosol concentrations increase, stay the same

or decrease.

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* How strongly features of the climate (e.g. temperature, precipitation and sea

level) respond to changes in greenhouse gas and aerosol concentrations.

* How much the climate varies as a result of natural influences (e.g. form

volcanic activity and changes in the suns intensity) and its internal variability

(referring to random changes in the circulation of the atmosphere and oceans).

Climate changes Impact on Agriculture

Climate change and agriculture are interrelated processes, both of which

take place on a global scale. Global warming is projected to have significant

impacts on conditions affecting agriculture, including temperature,

precipitation and glacial run-of. These conditions determine the carryingcapacity of the biosphere to produce enough food for the human population and

domesticated animals. Rising carbon dioxide levels would also have effects,

both detrimental and beneficial, on crop yields. The overall effect of climate

change on agriculture will depend on the of global climate changes on

agriculture might help to properly anticipate and adapt farming to maximize

agricultural production. Despite technological advances, such as improved

varieties, genetically modified organisms, and irrigation systems, weather is

still a key factor in agricultural productivity, as well as a soil properties and

natural communities. The effect of climate on agriculture is related to

variability in local climate patterns. The earths average surface temperature

has increased by 1degree F in just over the last century.

On the other hand, Agricultural trade has grown in recent years, and

know provides significant amounts of food, on a national level to major

importing countries, as well as comfortable income to exporting ones. The

international aspect of trade and security in terms of food implies the need to

also consider the effects of climate change on a global scale. More favorable

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effects on yield tend to depend to a large extent on realization of the

potentially beneficial effects of carbon dioxide on crop growth and potential

yields is likely to be caused by shortening of the growing period, decreases in

water availability and poor vernalization. In the long run, the climate change

could affect agriculture in the following ways:

1. Productivity, in terms of quantity and quality of crops.

2. Agricultural practices, through changes of water use (irrigation) and

agricultural inputs such as herbicides, insecticides and fertilization.

3. Environmental effects, in particular in relation of frequency and intensity of

soil drainage(leading to nitrogen leaching), soil erosion, reduction of

crop diversity

4. Rural space, through the loss and gain of cultivated lands, land speculation,

land renunciation, and hydraulic amenities.

5. Adaptation, organisms may become more or less competitive, as well as

humans may develop urgency to develop more competitive organisms,

such as flood resistant or salt resistant varieties of rice.

Agriculture and Food Supply

Agriculture is highly sensitive to climate variability and weather extremes,

such as droughts, floods and severe storms. The forces that shape our climate

are also critical to farm productivity; Human activity has already changed

atmospheric characteristics such as temperature, rainfall, levels of carbon

dioxide and ground level ozone. The scientific community expects such trends

to continue. While food production may benefit from a warmer climate, the

increased potential for drought, floods. Additionally, the enduring changes in

climate, water supply and soil moisture could make it less feasible to continue

crop production in certain regions.

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International Policy Issues

The development of climate change policy in India is occurring largely as

response to international developments, particularly the development of

international policies to manage greenhouse gas loadings in the atmosphere being

promoted by the Nations. In order to understand how India policy is likely to

develop an the background to Ministry for the Environment initiatives, it will be

helpful to review the current status of international policies. This is done most

easily by considering the Framework Convention on Climate Change (FCCC).

India along with 176 other countries has endorsed the FCCC which was

finalise at the United Nations Conference on Environment and Development in

Rio de Janeir in June 1992. This convention will go for-ward for approval by the

United Nations General Assembly and become legally binding on its signatories

once there is 50 c more of these.

The primary objective of the FCCC (INC, 1992) is to "achieve . . .

stabilization of greenhouse gas concentrations in the atmosphere at a level that

would prevent dangerous anthropogenic interference with the climate system."

The timing for achieving this objective is specified only as within a time

frame sufficient to allow ecosystems to adapt naturally to climate change, to

ensure that food production is not threatened and to enable economic development

to proceed in a sustainable manner".

The FCCC reaffirms a principle of international law that, while states have

authority within their own boundaries they have a responsibility to avoid

damaging the interests of other states. This pre-empts a -winners and losers"

approach to global climate change For example several studies indicate that highly

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developed countries, such as the USA might be able to adapt to anticipated climate

change under "business as usual" scenario: However, their endorsement of the

FCCC recognizes a responsibility to potential ''Losers under climate change, and

accepts at least an implicit commitment to reduce an ultimately prevent further

climate change.

The general form of commitment accepted by all signatories to the FCCC is

spelled out in article 4 of the convention through which they undertake, among

other things, to make available national inventories of anthropogenic emissions by

sources and removals by sinks of all greenhouse gases not covered by the

Montreal Protocol; and to cooperate in the development and transfer of technologyfor control of greenhouse gases in all sectors including energy, transport, industry,

agriculture, forestry and waste management sectors; and to cooperate in

adaptation to climate change and develop integrated plans for coastal zone

management, water resources and agriculture; Under article 4 of the FCCC

developed countries (including India) undertake rather more specific commitments

to adopt national policies for "modifying longer term trends in anthropogenic

emissions .... recognizing that the return by the end of the present decade to earlier

levels of anthropogenic emissions of carbon dioxide and other greenhouse gases ...

would contribute to such modification". And "each of these parties shall

communicate . . . detailed information on its policies .... as well as on its resulting

projected anthropogenic emissions by sources and removals by sinks of

greenhouse gases . . . . with the aim Of returning individually or jointly to their

1990 levels of these anthropogenic emissions".

This last commitment is the one that will cause the most pressure in the

near term for nations to limit greenhouse gas emissions. In particular compilation

and publication of national greenhouse gas emission inventories, in an

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international environment that is placing higher values on conservation and

sustainability ethics, will provide the strongest political pressure to act on climate

change issues in the next 5 years. Article 12 of the MCC gives more details of

procedures for submission of emission inventories and plans for reducing

emissions. A methodology for preparing national emission inventories has already

been well developed by study Groups operating under the auspices of the OECD

and the Intergovernmental Panel on Climate Change (IPCC), e.g. see OECD 1991,

and it seems clear that this will be used by the United Nations as a basis for

obligations under the FCCC.

The present methodology for preparing and submitting greenhouse gasemission inventories treats each greenhouse gas, e.g. CO, methane, or nitrous

oxide, separately. Emissions for each of the major Greenhouse gases are

categorized by the type of activity that produces the emission. This includes a

category for agriculture.

A significant amount of work has been carried out to develop a measure of

the total Greenhouse gas climate forcing from a single nation or technology. This

means that emissions from different greenhouse gases have to be combined. The

IPCC 1990 report endorsed the concept of a "Global Warming Potential" (GWP)

for this purpose. The GWP is different for each greenhouse gas and measures the

greenhouse effect forcing of that gas relative to the same mass Of CO2 -i.e., it

enables emissions of each gas to be expressed in C02 equivalents. The GWP

concept is discussed in more detail in the following subsection, 2.1.4., but for themoment it is important to recognise that the GWPs for different greenhouse gases

are subject to considerable uncertainty, both conceptual and numerical. Despite

these difficulties there is clearly a desire within the international science and

environmental communities to use GWPs or some similar weighting factor to

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combine emissions and thus establish protocols for monitoring a the total

greenhouse gas forcing from each nation. Even before there is agreement on this

use, we expect GWPs to be used in assessing the environmental value of trading

emissions in one greenhouse gas for emissions in another. Thus it is widely

recognized that burning methane at an emission source such as a landfill reduces

greenhouse effect forcing (and thence emissions of CO2 equivalents) and is

therefore a desirable goal.

The short-term obligations under the FCCC are for each developed nation

separately to reduce its greenhouse gas emissions. Clearly governments have the

authority to choose different ways of achieving this, ranging from "command

control" philosophies to targeted "market intervention" with intermediate policies

available. The implications of government policies on agriculture in this regard are

the main subject of this report.

In addition to controlling greenhouse gas emissions country by country,

consideration is also being given to controlling emissions internationally through

partnership arrangements. In particular proponents of "tradeable emission permits"

see this as a way of allowing some countries, for which the cost of greenhouse gas

reduction might be relatively high, to in effect purchase greenhouse gas reductions

made in countries where the costs were relatively low. This would be done in such

a way that the combined emissions of all countries involved was kept to an agreedlevel. This system could obviously be developed into an international market in

greenhouse gas emission quotas

To summarize the international policy issues from a India perspective:

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The main political pressure to act on climate change in the short term will

come through compilation and publication of greenhouse gas emission

inventories, broken down by economic sectors;

India is free to choose its own approach to limiting greenhouse gas

emissions, the only external pressure being that these should be seen to be

effective. There is still a debate over the relative merits of a "carbon tax" or

"tradeable emission permits" both nationally and internationally;

We should anticipate international agreement on a methodology for

combining emissions of different greenhouse gases to arrive at a total

greenhouse forcing figure for each economic sector, including agriculture.

This will weight methane emissions about 15 to 20 times more heavily thanemissions of the same mass of CO2;

There may become an international market in greenhouse gas emission

quotas which will provide export potential for greenhouse gas "sinks"

particularly to heavily industrialised countries.

Combining Greenhouse Gases - The Global Warming Potential Issue

It is known that incremental additions to the atmosphere of many of the non-

CO2 greenhouse gases, such as methane or nitrous oxide, are much more potent

greenhouse effect forcers than an increment of CO2 itself. This is principally

because each is much more effective, molecule for molecule, at trapping long-

wave radiation that would otherwise escape to space. This is partially offset in

some cases, notably methane, by the much shorter lifetime (e.g. methane about 10

years) than CO2 (about 120 years). A measure of the relative potency is the 'Global

Warming Potential' (GWP) for each gas.

The GWP for a greenhouse gas is a measure of the impact of that gas on

the greenhouse effect relative to the same amount of CO2. IPCC (1990) defines the

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GWP as: "the time integrated commitment to climate forcing from the

instantaneous release of 1 kg of a trace gas expressed relative to that from 1 kg of

carbon dioxide". The 1992 Supplement Report of the IPCC (IPCC 1992)

essentially continues with this definition. In fact this definition is incomplete

(Manning, 1991) and practical calculations implicitly use slightly different

definitions. The simplest calculations of GWP (e.g. Rodhe, 1990) are based on the

direct radiative forcing, that is the additional infra-red radiation absorbed, due to 1

kg of the greenhouse gas and integrated over time, expressed relative to the

corresponding value for 1 kg of CO2. If this is taken over a very long time then in

effect the GWP is the product of two terms, one being the additional infra-red

radiation absorbed and the other the average residence time of an increment of the

gas in the atmosphere, divided by the same two terms evaluated for CO2.

One complication in the definition of GWPs is that it is not possible to

calculate the "time integrated commitment" unless some fixed horizon is set

limiting the period being considered. A GWP will depend upon the 'time horizon'

over which the commitment is accumulated. The 'time horizon' refers to future

time after emission during which the greenhouse effect forcing of the gas is

considered and beyond which it is ignored. A GWP will depend quite strongly

upon the time horizon if the atmospheric lifetime of the gas in question is

comparatively short. An increment of CO2 to the atmosphere has an extremely

long residence time there, and in most mathematical models this is strictly infinite.

But for methane in particular, the residence time is much shorter, at about 10

vents. The effect of this is that when GWPs are calculated over time horizons of a

few decades only part of the long-term effect of CO2 is taken into account and the

GWP is correspondingly larger than for a several-century horizon.

The IPCC (1990) definition of GWP and most recent calculations

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include additional "indirect effects" due to chemical interactions of the gas in the

atmosphere. While CO2 does not have such indirect effects methane in particular

does: methane emissions lead to additional water vapour in the lower stratosphere,

increases in tropospheric ozone, and reduction of the oxidising power of the

atmosphere (Manning, 1991; Lelieveld and Crutzen, 1992). The IPCC (1990)

report had included an estimate of indirect effects in its methane GWP. IPCC

(1992) adjudged that the calculation of these indirect effects was not yet

sufficiently understood to be incorporated in GWPs. The value of 11 is quoted for

the "direct" component of the methane GWP over a time period of 100 years, and

the statement made that the indirect effect is positive "possibly as large as thedirect effect". Thus there is no agreed number for the GWP of methane at this

stage. Lelieveld and Crutzen (1992) using different atmospheric chemistry

scenarios calculate full GWPs of 15 and 20. Manning (1991) has estimated similar

values of 16 and 21 considering additional unpublished work.

Table 1. Reports the GWPs for the important agriculturally sourced greenhouse

gases methane (CH4) and nitrous oxide (N20), for time horizons of 20, 100 and

500 Years, taken from IPCC (1992).

Table 1 Direct GWPs for agriculturally important greenhouse gases

(from IPCC, 1992)

Gas Residence Time Direct GWP for Time Horizons of:

20 year 100 year 500 year

CO2 approx 120 yr 1 1 1

CH4 10.5 yr 35 11 4

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N2O 132 yr 260 270 170

Despite these potential ambiguities in how GWPs are defined, one should

anticipate general agreement to use GWPs for about 100 year horizons. In this

report we have weighted emissions of methane simply by the direct GWP 11, toproduce CO2 equivalent emission. This is done on the basis that there are many

other uncertainties in the calculations involved, and in the face of the lack of any

internationally accepted GWP for methane. However, we expect that if final

GWPs for methane are agreed internationally, and the 100 time horizon is used,

then these will be around 15 to 20 and the greenhouse impact of methane will be

taken to be proportionally larger. On the other hand, there may be a trade off

between the increase due to indirect effects and a decrease due to adapting a

longer time horizon eg. 150 to 200 years.

Agriculture and Climate Change Mitigation

Regardless of the projected or actual impacts of climate change,

agriculture is also likely to be directly or indirectly involved in climate change

mitigation efforts. Greenhouse gas emissions (GHGE) constitute a globalproduction externality which is likely to adversely affect climate. The UNFCCC is

trying to negotiate net GHGE emission reductions. Actions under that convention

yielded the Kyoto Protocol which represents the first significant international

agreement towards GHGE reduction. Agriculture (using a definition including

forestry) is mentioned as both an emitter and a sink in the protocol. Annex lists

agriculture as an emission sources from enteric fermentation, manure

management, rice cultivation, soil management, field burning, and deforestation.

The protocol also lists agriculturally related sinks of afforestation and

reforestation. Additional sources and sinks are under consideration including

agricultural soil carbon.

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Ways Agriculture would be Affected by Climate Change Mitigation

Following the arguments in McCarl and Schneider (1999,2000a), there are at least

four ways agriculture may participate in or be influenced by greenhouse gas

mitigation efforts.

! Agriculture may need to reduce emissions because it releases substantial

amounts of methane, nitrous oxide, and carbon dioxide.

! Agriculture may enhance its absorption of GHGE by creating or expanding

sinks.

! Agriculture may provide products which substitute for GHGE intensive products

displacing emissions.

! Agriculture may find itself operating in a world where commodity and inputprices have been altered by GHGE related policies.

Each of these are discussed briefly in the following section

Agriculture - A source of greenhouse gases

The IPCC (1996) estimates that globally agriculture emits about 50% of total

methane, 70% of nitrous oxide, and 20% of carbon dioxide. Sources of methane

emissions include rice, ruminants and manure. Nitrous oxide emissions come from

manure, legumes, and fertilizer use. Carbon dioxide emissions arise from fossil

fuel usage, soil tillage, deforestation, biomass burning, and land degradation.

Contributions across countries vary substantially, with the greatest differences

between developing and developed countries. Deforestation and land degradation

mainly occurs in developing countries. Agriculture in developed countries uses

more energy, more intensive tillage systems, and more fertilizer, resulting in

fossil-fuel based emissions, reductions in soil carbon, and emissions of nitrous

oxides. In addition, animal herds emit high methane from ruminants and manure

(IPCC (1996) and McCarl and Schneider (1999,2000a) elaborate).

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Agriculture - A sink for greenhouse gases

The Kyoto Protocol allows credits for emission sinks through afforestation

and reforestation. Provisions allow for consideration of additional sources and

sinks. Agriculture can serve as an emission sink in mainly offsetting CO2

emissions. Management practices can increase soil carbon retention (commonly

called carbon sequestration). Such practices include land retirement (conversion to

native vegetation), residue management, less-intensive tillage, land use conversion

to pasture or forest, and restoration of degraded soils. While each of these can

increase the carbon-holding potential of the soil, some issues are worth noting.

Soils can only increase carbon sequestration up to a point. Retained carbon

increases until it reaches a new equilibrium state that reflects the new managementenvironment. As the soil carbon level increases, soil absorption of carbon

decreases and soil potential to become a future emission source since subsequent

alteration of the management regime can lead to carbon releases. Third, enhanced

carbon management can reduce agricultural productivity. (IPCC 1996, 2000,

Marland, McCarl and Schneider (1998) and McCarl and Schneider (1999,2000a)

elaborate).

Agriculture - A way of offsetting net greenhouse gas emissions

Agriculture may provide substitute products which replace fossil fuel

intensive products. One such product is biomass for fuel usage or production.

Biomass can directly be used in fueling electrical power plants or maybe

processed into liquid fuels. Burning biomass reduces net CO2 emissions because

the photosynthetic process of biomass growth removes about 95 percent of CO2

emitted when burning the biomass. Fossil fuel use, on the other hand, releases 100

percentof the contained CO2. Substitute building products can be drawn from

forestry reducing fossil fuel intensive use of steel and concrete. (Marland and

Schmalinger(1997) elaborate). Cotton and other fibers also substitute for

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petroleum based synthetics.

Agriculture - Operating under fuel taxes

The need to reduce emissions and the implementation of emissions

trading will likely affect fossil fuel prices. For example, diesel fuel distributors

might need to purchase an emissions permit, effectively raising fuel prices.

Similarly, the US might implement some sort of fuel tax. The tax and

corresponding transportation cost increases might influence the cost of petrol-

based agricultural chemicals and fertilizers as well as on-farm fuel prices and off-

farm commodity prices.( McCarl, Gowen and Yeats(1999), USDA(1999), Antle et

al (1999), and Konyar and Howitt(2000) elaborate)

Economic Appraisal of Agricultural Effects of Climate Change Mitigation

Actions

A number of climate change mitigation impact studies have been done

although this is very much an emerging literature. McCarl and Schneider

(1999,2000a) provide a review. Across that literature a number of general findings

have emerged.

Agricultural emission reductions and offsets can be cost effective strategies

for GHGE offsets at relatively lower carbon prices. McCarl and Schneider(2000a)

amass substantial evidence for the aforementioned emission reductions and

sequestration options. Recent studies by Pautsch et al (2000), Antle et al (2000)

and McCarl and Schneider (2000b) show low cost potential for agricultural soil

carbon sequestration. The literature cited by D.M. Adams et al(1999) as well as

their numerical results show low cost potential in forest soils and standing timber.

Agriculture can operate in the face of carbon induced fuel price increases

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without great dislocation as shown in the studies by McCarl et al (1999),

USDA(1999) and Antle et al (1999). Konyar and Howitt (2000) show greater

sensitivity but use a $348 per ton carbon price. Francl (1997) shows large net

income losses but used an analytic framework which embodied assumptions

precluding adjustments in either market consumption behavior or production

patterns.

Agricultural emission offsets are competitive with food production. For

example McCarl and Schneider (2000b) find substantial decreases in food

production and increases in food prices at higher carbon prices. Similarly, Konyar

and Howitt(2000) show consumers effects at high carbon price induced fuel taxes.Agricultural soil and forestry based carbon sequestration can be competitive at low

carbon prices. Thus, there is real potential that management and the allocation of

land between forestry and agriculture may be affected by climate change

mitigation efforts. However, while Lal et al (1998) and others provide large

estimates for the potential of carbon sequestration based on land potential in both

of these arenas, studies have shown that at lower carbon prices the realized

sequestration acreage is substantially lower than the total estimated potential. (See

D.M. Adams et al (1999), McCarl and Schneider(2000b), Babcock and

Pautsch(1999) and Antle et al (2000) in contrast with Lal et al 1998 for evidence).

Across the array of potential agricultural emission reduction, substitution

and offset alternatives, there are alternatives with substantially different economic

potential. In particular in the study by McCarl and Schneider(2000b) the

replacement of power plant coal fired electricity generation with biofuels plays a

substantial role but only at carbon prices above $60 per ton while at low prices

agriculturally based soil carbon sequestration, afforestation and fertilization

modifications dominate the set of best strategies. In that study methane and

ethanol strategies exhibited low potential.

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Mitigation activity stimulated by carbon price increases generally improves

producers welfare and decreases consumers welfare (See the results in McCarl

and Schneider(2000b

Documents

Thesis on Climate Change and Its Impact on Agricultural fields