Agricultural drought: Climate change and rainfed agriculture

Abstract

Increasing evidence over the past few decades indicate that significant changes in climate are taking place worldwide as a result of enhanced human activities. The inventions that were discovered during last few centuries, more so in the last century has altered the concentration of atmospheric constituents that lead to global warming. The major cause to climate change has been ascribed to the increased levels of greenhouse gases like carbon dioxide (CO2), methane (CH4), nitrous oxides (NO2), chlorofluorocarbons (CFCs) beyond their natural levels due to the uncontrolled activities such as burning of fossil fuels, increased use of refrigerants, and enhanced agricultural related practices. These activities accelerated the processes of climate change and increased the mean global temperatures by 0.6°C during the past 100 years, a phenomenon known as global warming. It has also induced increased climatic variability and occurrence of extreme weather events in many parts of the world. Studies indicate that the years viz., 1997, 1998 and 1999 during the past century, recorded more warmer conditions across the globe, and the process continued in this decade also. Summer 2002 and 2003 were declared as warmest years on record by NOAA especially in the Asian sub continent and in Europe where the temperatures remained extremely high for long periods resulting in death of 20,000 human populations in Europe alone. Scientists attribute this to a long-term warming trend over the globe. In large part of Asia, agricultural production is mainly dependent on the monsoonal rains. Evidences also indicate that large-scale climatic variations are prevalent at micro-regional level influencing the rainfall distribution in different parts of Asia. The causes of these regional climate changes vary from global to region level. It is evident that there was, there is and there will be climate variability at global, regional and local levels. Since climate is closely related to human activities and economic development including agricultural system, there is a serious concern about its stability (Sinha et al., 2000). The awareness of the magnitude of the impact of climate change on society by the various governments led to adoption of an International Convention on Climate Change by United Nations in 1992. Article 2 of this convention called the UN Framework Convention on Climate Change (UNFCCC) makes two relevant stipulations relevant and important to agriculture, which is (a) prevent dangerous anthropogenic interference with the climatic system, and (b) to ensure that food production is not threatened. The two are related and need in-depth analysis. The global climate system is a consequence of a link between the atmosphere, the oceans, the biosphere, the cryosphere, and the geosphere and any change to this system produced by forcing agents - results in climate change. Some of the atmospheric constituents such as water vapour, carbon dioxide, methane, and nitrous oxide are transparent to short wave solar radiation and opaque to 331 long wave radiation emitted by earths surface, thus, trapping the heat from sunlight near the Earth's surface known popularly as green house effect. This effect keeps the planet 33°C warmer than it would otherwise be, allowing the earth to support life. With the advent of the industrial revolution, there has been a tremendous growth in the fossil-fuel utilization leading to increased carbon dioxide emissions over the globe especially since 1950s. In addition to this, the emission of chlorofluorocarbons (CFCs) and other chlorine and bromine compounds used in refrigeration and other industrial uses not only have an impact on the radiative forcing, but also have led to the depletion of the stratospheric ozone layer. Land-use change, due to urbanization and deforestation and agricultural practices, affect the physical and biological properties of the Earth’s surface. Such effects also change the radiative forcing and have a potential impact on regional and global climate.