Int. J. Environ. Res. Public Health 2009, 6 1. Introduction 2398 Global warming, which is the gradual increase in world temperatures caused by greenhouse gases (GHGs) such as carbon dioxide, nitrous oxide, chlorofluorocarbons, methane, sulphuric fluoride and some organochloride compounds, released by anthropogenic activities, has attracted the attention of environmental scientists around the world. GHGs trap solar energy in the atmosphere, causing the temperature to rise (greenhouse effect). GHGs, ordinarily, are vital to life sustenance on Earth due to heating effects but the Industrial Revolution has increased their emissions, hence the environmental concerns. The forecast on global temperature increase is put at 1 to 3 °C in the next few decades given that the Earth’s temperature is likely to rise by about 0.1 to 0.2 °C per decade [1,2]. Global warming is projected to cause changes in different environmental processes including sea level rises, amount and pattern of precipitation, lowering of ocean pH, oxygen depletion in oceans, expansion of subtropical deserts, retreat of glaciers and sea ice, shrinkage in rainforests, increases in the intensity of extreme weather events, species extinctions and changes in agricultural yields. These will result in a wide variety of crisis situations including food crisis, referring to declines in food security and safety. The impact of global warming on agriculture could be direct, by causing instant plant death, or indirect by impacting factors that have bearing on crop productivity and soil sustainability. The increasing demand for organic foods produced using organic fertilizer has led to the utilization of different organic materials including sludge, agricultural, household and municipal solid wastes for compost formulations [3,4] for fertilization purpose. Heavy metals such as cadmium (Cd), lead (Pb), mercury (Hg), arsenic (As), chromium (Cr), nickel (Ni), zinc (Zn) and copper (Cu), which are found in the different spheres of the environment (air, water and soil) are also found in composted waste materials arising from the raw substrates used in production. As a result of repeated compost application to soils, heavy metals whose health hazards range from developmental retardation, various cancers, kidney damage to death [5] could accumulate in soils, be transported to nearby surface water or groundwater [6,7] and can eventually cause contamination of human and other animal food chains. Most importantly, it could enhance plant metal uptake and accumulation in their tissues, resulting in phytotoxicity and ultimately, reduced crop productivity. An appreciation of heavy metal effects from composts would be better achieved from the perspective of different chemical forms (speciation) of metals present in the bulk compost, which include water-extractable, exchangeable, fraction bound to organic matter or minerals, more than just the total metal concentration. Water-extractable and the exchangeable metal fractions in composts provide qualitative information on mobility and bioavailability with the former being more readily available for plant uptake than the latter. The distribution of metals in these forms in the composted wastes and their subsequent release are affected by factors such as pH, reduction-oxidation potential, the presence of competing ions, complexing ligands, time and temperature [8,9]. Despite several literature reports on pot and field experiments on compost usage [10-17], there is a paucity of information on temperature effects on heavy metal release from composted organic matter, utilized as soil amendments. Previous experimental designs were largely focused on uptake, accumulation and distribution of heavy metals in crops grown in compost amended soils.