Agriculture Reference
In-Depth Information
first example relates to Svante Arrhenius (1859-1927), a Swedish physical chemist
who in 1895 theorized about the influence of carbonic acid in air on surface tempera-
tures as a way to explain past climate changes. His work described a model of energy
balance that included the effects of the absorptive power of CO
2
and water vapor for
long-wave, infrared radiation and its possible effects on the temperature of terrestrial
surfaces. The second is C. David Keeling (1928-2005), an American chemist who in
1958 established a laboratory in Mauna Loa, Hawaii, for accurate measurements of
CO
2
concentrations in air samples and demonstrated throughout the years the con-
nection between human activities and the chemical composition of the atmosphere
(Keeling, 1960; Le Treut et al., 2007).
Today, and as a consequence of decades of research and observations, we know
that the Earth is warming, and that this warming could bring undesired consequences
on life as we know it. In May 2007, the Intergovernmental Panel on Climate Change
(IPCC) (IPCC, 2007) announced the latest advancements in the state of knowledge
of anthropogenic climate change (www.ipcc.ch). This report, the fourth in a series
that started back in 1990, represented the culmination of almost 20 years of con-
tinuous activity of the international community assembled under the IPCC geared
toward the comprehensive, objective, and transparent evaluation of the scientific,
technical, and socioeconomic basis of anthropogenic climate change, its impacts,
and options for its mitigation and adaptation.
One of the outstanding conclusions of Working Group I (WG I)—in charge of
the studies related to the origin and causes of climate change—was to assert with
a “high degree of confidence” that human activities since 1750 have induced a net
warming effect over the Earth that translates into a “radiative power” of 1.6 (range
0.6 to 2.4) W m
−2
(Solomon et al., 2007). This increase in radiative forcing
1
is due
primarily to the continuous increase in emissions of three “trace” greenhouse gases
since the beginning of the industrial period: carbon dioxide (CO
2
), methane (CH
4
),
and nitrous oxide (N
2
O).
The high degree of confidence about the occurrence of global warming of the
climate system is based on observations of temperature increases in the atmosphere
and oceans, ample evidence of sea ice and glacier melting, and sea-level rise. This
global warming is also expressed in changes in the spatial distribution and magni-
tude of precipitation, salinity of ocean water, distribution and intensity of winds, and
in general an increase in extreme events such as droughts, floods, and heat waves
and in the intensity of tropical cyclones (Rosenzweig et al., 2007). Figure 16.1, from
IPCC AR4 (Solomon et al., 2007), portrays a sophisticated analysis with respect to
the evolution of greenhouse gases throughout hundreds of thousands of years before
the present. The figure reveals the genuine increase in atmospheric concentrations
of three greenhouse gases during recent years due mainly to the incessant increase
in fossil fuel combustion and the conversion of tropical forests into pasturelands or
croplands.
Agriculture is one human activity that should be responsive to climate change.
In its most basic essence, agriculture consists of the guided capture of solar energy
through domesticated plants (crops) and in the transformation of this energy into
plant- or animal-based food, fiber, or bioenergy products. Thus, the changes in tem-
perature, precipitation, cloudiness, windiness, and so on anticipated to occur during
