There are many horrible things that could occur. As a previous post mentioned, ocean levels would rise due to melting ice caps. In addition, oceans absorb more heat than land and this would contribute to rising sea levels as well. Because of this, coastal cities and towns could flood and be destroyed. It would also be very damaging to many habitats. Many lakes and rivers may dry up, possibly causing the extinction of many species. Droughts may occur making is very hard or impossible to grow crops. People may go hungry or even starve. Bad weather may also become more frequent, such as hurricanes and volcanoes.
Global warming is a scary topic to think about. That is why there has been so much debate regarding it. Some people are still not on board with the theory. They believe that we are just cycling through a normal transition. Personally, I believe we have done some significant damage to our environment.
Global warming will increase the sea levels due to the polar ice caps melting. "It will also change the amount and pattern of precipitation, probably including expansion of subtropical deserts." The frequency and intensity of weather patterns will change, becoming more dramatic. Agriculture will be impacted, with less food being produced due to climate change. People's health will be impacted by the heat waves in the summer and extreme cold spells in the winter. Temperature has an impact on vector-borne diseases such as malaria, dengue fever, yellow fever, and encephalitis. Air quality will be effected causing significant respiratory problems for individuals. "Ground-level ozone can damage lung tissue, and is especially harmful for those with asthma and other chronic lung diseases."
It's not so much the global warming itself that results in negative consequences for life on Earth, but rather the Climate Change that comes about because of it. We don't fully understand the complete impact over time, and it will vary based on how much the temperature warms in the next 50 years, but some of what is predicted is a change in precipitation patterns - extended drought or extended rain/snowfall in places where that is unusual. Stronger hurricanes and cyclones as they feed on the warm water.
The biggest potential effect will be with animal, plant and insect species, as the climate may change too quickly for many of them to adapt, thus leading to their extinction. Since we don't fully understand the food chains, some of these animals will disrupt our food supply as well. The honeybee is a good example of a species that is already struggling, and we rely on it to pollinate many of our food crops.
Some rather obvious evidence of global warming taking place is the rapid disappearance and shrinking of glaciers around the globe.
Global warming results in increase in average temperature across the world. This will change many set patterns of weather and climate across the world. This in turn will effect the ecology of the various regions affecting their plant and animal life. But this is the not the biggest problem of global warming. The biggest harm of global warming will be caused by the melting of the polar ice caps. When this happens the level of water in all oceans and seas of the world will rise, submerging all the coastal areas that is home to nearly 15 percent of the world population. This process is unfortunately irreversible. That means once the polar ice cap melts, it will not form again even if the global temperature return to the current levels.