Global warming is the long-term rise in temperature of the air and the oceans that is currently occurring due mainly to the increasing concentrations of greenhouse gases in the atmosphere. Although the terms are often used interchangeably, it is just one aspect of climate change, which refers to the increasing long-term changes in climates, including not only temperature but also precipitation and wind patterns.
Global warming is mostly a result of human activity, especially the ever-increasing burning of fossil fuels and deforestation. Average temperatures today are about one degree centigrade higher than before the start of large-scale coal burning around 1750, with most of this increase having occurred during the past half century, and there is scientific consensus that with continued unmitigated greenhouse gas emissions the average will have risen by several additional degrees by the year 2100.*
This higher temperature has multiple harmful effects. One is increasing the levels of water in the oceans, both because of the melting of the polar ice caps and glaciers and because water expands as its temperature rises. Higher ocean water levels can damage coastal coastal communities and can eventually make some of them uninhabitable. They can also harm estuaries and other fragile coastal ecosystems, thus contributing both to extinctions and causing economic damage by reducing the harvest of fish and other animals that live there. In addition, higher sea levels will increase the intrusion of saltwater into fresh water aquifers, thereby putting further pressure on the water supplies available for agriculture and other uses.
Warmer temperatures will also increase extinctions because many species of animals and plants are highly sensitive to temperature. In addition, they may lead to increased incidence of diseases, because many diseases and the vectors that transmit them, such as some species of mosquitos, are prevalent in the warmer climates.
Moreover, higher temperatures will result in increased demand for air conditioning, which will require more electric power generation, which typically has adverse environmental effects. But air conditioning will remain unaffordable for a large portion of the world's population, thus resulting in increased death rates.
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*"What is Climate Change?," World Bank Climate Change Knowledge Portal, 2021, https:// climateknowledgeportal .worldbank.org /overview.