CLIMATE VARIABILITY, AGRICULTURE AND REMOTE SENSING - Food Security, Food Prices and Climate Variability - page 50

Climate variability can bring extremes in weather that lead to droughts, floods and other
natural weather events. These extremes can be exacerbated by the underlying trends in the
climate. Variability is caused by planetary-scale trends and cycles in the earth's land, ocean,
atmosphere and life processes. Some of these cycles are multi-year events such as the El Nino
Southern Oscillation or ENSO, the north Atlantic oscillation, and other cycles that result
from longer-term ocean circulation (Chen et al ., 2004). Climate cycles can cause several
months of unusually wet or dry weather in a community. These extreme events can have a
profound influence on agricultural production and livelihoods of people who rely on natural
resources for their living (Chimeli et al ., 2002). When these cycles occur in places already
experiencing trends in rainfall due to climate change, it can result in economically significant
shifts in species if dry or wet conditions due to climate cycles interact with longer-term
trends, resulting in long periods of extreme conditions (Gutschick and Bassirirad, 2003;
Tschirley and Weber, 1994; Katz and Brown, 1992).
Global environmental change is a concept that connects large-scale changes in human
society with natural and anthropogenic changes in natural systems. The International
Geosphere-Biosphere Programme (IGBP) was established in 1987 to coordinate international
research on global- and regional-scale interactions between human systems and the earth's
biological, chemical and physical processes (IGBP, 2012). As Steffen et al. (2012) state in the
executive summary of their book:
Begun centuries ago, this transformation has undergone a profound acceleration during
the second half of the 20th century. During the last 100 years human population soared
from little more than one to six billion and economic activity increased nearly 10-fold
between 1950 and 2000. The world's population is more tightly connected than ever
before via globalization of economies and information flows. Half of earth's land surface
has been domesticated for direct human use.
These changes are likely to have a profound impact on agriculture, as humanity erodes the
soil, pollutes the water and changes the ecological systems on which agriculture is based
(Steffen et al ., 2012).
Measuring climate variability that is relevant to agriculture is challenging. Determining
how likely it is a single farm will experience drought in a particular year may require three
decades of high quality meteorological data as well as a comprehensive understanding of the
amount of moisture the crop being planted requires for optimal growth (Zell et al ., 2012).
Climate data records, or a time series of measurements of sufficient length, consistency and
continuity to determine climate variability and change, are needed in order to determine how
a location is changing (NAS, 2004). Even with adequate meteorological data, understanding
the amount of moisture required for a particular crop necessitates measurement of the soil
composition, humus and organic content of the soil, rooting depth of the crop and the spe-
cific genetic makeup of the plant variety (Deryng et al ., 2011; Wit and Diepen, 2007; Rojas,
2007; Hansen and Indeje, 2004). Underlying trends in soil characterstics due to a lack of
replenishment of nutrients, in the characteristics of the crop being planted or in the climate
variability itself will reduce our ability to estimate the impact of climate variability on food
production.
As the global population and economy has expanded, agriculture has moved into areas
where climate variability has more impact. This expansion, coupled with improvements in