According to About.com, there are several disadvantages of global warming. These disadvantages include disrupted ocean circulation, higher sea levels leading to flooding, increased desertification, changes to agricultural production, water shortages, starvation and malnutrition due to food and crop shortages, increased disease, increased deaths due to heat wave, additional animal and plant extinction, additional energy usage, increased pollution, increased allergy rates, rainfall acidity and a higher cost of insurance.
According to Discovery.com, the worst effect global warming is likely to have is the destruction of the ecosystem. Threats to supplies of fresh water and clean air, as well as to energy, food and medicine are likely to threaten not just human lifestyles but survival itself. Additional serious and negative effects caused by global warming are the concomitant loss of biodiversity, with 30 percent of the species alive today at risk should average temperatures continue to rise, causing the loss of habitats needed for those species to survive.
Discovery.com points out that scientists have concluded that if global warming continues, no part of the world will be free of its effects. Effects of global warming such as the bleaching and death of coral reefs are already being noticed. If these effects continue to occur, humans may be forced to fight for diminishing resources.