The rising of sea levels is one of the more common concern; taking place with a thermal expansion of the oceans – a result of water molecules expanding in warmer temperatures, increased precipitation, and the melting of mountain glaciers. Because all bodies of water have different and ocean water tends to "swell" differently depending on its starting temperature, the change in sea level is not uniform. In the 20th century alone, sea levels rose 0.17 meters predictions for the next century range anywhere from 0.18 to 0.59 meters.

Currently, the Arctic summer sea ice is about half as thick as it was in 1950. Just like an ice cube melting in a glass of water, the melting Arctic sea ice does not contribute to sea-level rise, except for the expansion of seawater with the heat increasing. However, melting of the Arctic sea ice may lead to global changes in ocean circulation. Water from melted ice forms a layer at the sea surface that is less dense than the underlying water since it is less salty. Additionally, melting sea ice speeds up the warming of the Arctic since water absorbs 80% of sunlight, about the same amount that the cover of sea ice used to reflect.

While the idea of swimming in a warmer ocean is pleasant to most human beings, increasing ocean temperatures could cause serious ecological damage. 

An increase in global temperature will likely cause severe weather, which could mean stronger and more frequent storms. Warmer temperatures cause more evaporation of water, which, as part of the water cycle eventually leads to increased precipitation and further increasing the chances of flooding. While some parts of the world are projected to experience increased precipitation, others may experience higher levels of drought as places that are typically dry experience even more evaporation as global temperatures increases. Scientists, however, are trying to determine whether drought is actually increasing or if we are experiencing a change in areas of drought.

Warmer winters mean that many deaths related to cold temperatures might be avoided and that the growing season will last longer, a possible benefit of  global warming. More people around the world die because of winter cold than because of summer heat. A decrease in winter deaths could offset a potential increase in summer heat-related deaths, or even lead to more lives saved as a result of the changed temperatures. With respect to longer growing seasons, there is already evidence in Europe that their growing season has been extended since the 1960s, with spring plants now blooming about 6 days earlier and fall colors coming 5 days later.

With drought affecting some regions and heat intensifying in the tropics, many areas will become unsuitable for agriculture. In tropical areas that are already dry and hot, the ability to harvest food will likely decrease even with small increases in warming. However, warmer temperatures and increased precipitation can also make more suitable for farming. Therefore, it is likely that, with a changing climate, a global change in the agricultural pattern will occur.

In addition to potential environmental changes, the human health implications of increased global warming are very concerning. Extreme heat waves in 2003 and 2006 led to thousands of deaths in Europe, North America, and India, which are likely to increase. We are also witnessing a renewed spread of diseases, likely to increase if temperatures continue to rise, including a spread of illnesses that were previously limited only to tropical areas.

Other species are also affected by global warming, most often by changes in migration patterns, shorter hibernation times, relocation to new areas, and extinction due to lack of adaptation. For example, many animals accustomed to living in the arctic regions have been forced further out of their native habitat in search of more accommodating places closer to the poles. Animals that migrate, such as birds and butterflies, have begun extending their migratory range closer to the poles, arriving sooner and departing later.