Introduction - Climate Resilient Agriculture for Ensuring Food Security - page 4

to human activity that alters the composition of
the global atmosphere and that is in addition to
natural climate variability observed over compa-
rable time periods.”
The IPCC defi nes climate change as a statisti-
cally signifi cant variation in either the mean state
of the climate or in its variability, persisting for
an extended period. Climate change may be due
to natural internal processes or external forcings
or persistent anthropogenic changes in the com-
position of the atmosphere or in land use.
Global climate change is a lasting change in
the statistical distribution of weather patterns
over periods ranging from decades to millions of
years. It may be a change in average weather con-
ditions or the distribution of events around the
average (e.g., more or fewer extreme weather
events). Climate change is a long-term shift in
weather conditions identifi ed by changes in tem-
perature, precipitation, winds, and other indica-
tors. Climate change can involve both changes in
average conditions and changes in variability,
including extreme events.
The earth's climate is naturally variable on all
time scales. However, its long-term state and
average temperature are regulated by the balance
between incoming and outgoing energy, which
determines the earth's energy balance. Any factor
that causes a sustained change to the amount of
incoming energy or the amount of outgoing
energy can lead to climate change. As these fac-
tors are external to the climate system, they are
referred to as “climate forcers,” invoking the idea
that they force or push the climate towards a new
long-term state - either warmer or cooler depend-
ing on the cause of change.
Agriculture is the basic activity by which
humans live and survive on the earth. Assessing
the impacts of climate change on agriculture is a
vital task. In both developed and developing coun-
tries, the infl uence of climate on crops and live-
stock persists despite irrigation, improved plant
and animal hybrids, and the growing use of chemi-
cal fertilizers. The continued dependence of agri-
cultural production on light, heat, water, and other
climatic factors, the dependence of much of the
world's population on agricultural activities, and
the signifi cant magnitude and rapid rates of possi-

ble climate changes all combine to create the need
for a comprehensive consideration of the potential
impacts of climate on global agriculture.

1.1.1 The Main Indicators of Climate

Change

There are seven indicators that would be expected
to increase in a warming world (Fig. 1.1 ):
• Temperature over land
• Ocean heat content
• Sea level
• Sea surface temperature
• Temperature over ocean
• Humidity
• Tropospheric temperature
There are three indicators that would be
expected to decrease in a warming world
(Fig. 1.1 ):
• Sea ice

• Snow cover

• Glaciers

1.1.2 Ten Key Indicators of a Human

Finger Print on Climate
Change

John Cook, writing the popular Skeptical Science
blog, summarizes the key indicators of a human
fi nger print on climate change (Fig. 1.2 ) as

follows:
• Less heat escaping to space
• Shrinking thermosphere
• Cooling stratosphere
• Rising tropopause
• Less oxygen in the air
• More fossil fuel carbon in the air
• 30 billion tons of CO 2 per year
• More heat returning to earth
• Nights warming faster than days
• More fossil fuel carbon in coral
The information based on the comparison of
atmospheric samples contained in ice cores and
more recent direct measurements provides evi-
dence that atmospheric CO 2 has increased since
the industrial revolution.