Definition of Global Warming

What Is Global Warming?

Strip away all of the political and emotional ideas you may have about global warming, and at its very core the term means the warming of the earth’s surface. Here’s an outline of the most basic issues behind the term global warming to give you a clearer understanding of what it is and how it affects your life.

Before we go too far, let’s clarify one common misconception: though the terms “global warming” and “climate change” are commonly used interchangeably, global warming is not synonymous with climate change. In fact, global warming is just one of the kinds of changes in climate that the earth has undergone and will continue to go through in the future.

You will most often hear the term global warming used to refer to a rise in the temperature of the earth’s surface air and oceans since the middle of the twentieth century and the concern over the earth’s continued temperature rise in the decades to come. The Intergovernmental Panel on Climate Change (IPCC), which is one of the most well-known scientific bodies studying global warming, tells us that global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) over the past century, with further rises in temperatures through the 21st century of 1.1 to 6.4 °C (2.0 to 11.5 °F). This might not seem like a lot, but even temperature changes this small could have dire consequences.

But why is the earth warming? Global warming is caused by the greenhouse effect, a phenomenon you may have already heard about in school or on the news. Normally, the earth absorbs some of the sun’s energy and reflects some of it back into space. However, by adding things like carbon dioxide (and other greenhouse gas emissions) and water vapor to the atmosphere, we make it much more difficult for that energy to escape out to space. In the end, this causes the lower atmosphere of the planet to warm like a greenhouse. Generally speaking, the more greenhouse gas emissions we pump into the atmosphere, the warmer our planet will become.

Most scientists agree that human activities are the major contributing factor behind global warming. IPCC and the National Academy of Sciences (NAS) in the US acknowledge that although natural drivers can add to changes in planetary climate, close to 98% of all global warming is caused by human activities, most importantly deforestation and the burning of fossil fuels (which release greenhouse gas emissions).[1]

One final clarification: the term “global warming” often causes people to assume that temperatures across the globe will warm evenly, creating balmier weather from nation to nation. But because of the intertwined nature of climate systems around the earth, this just isn’t the case. Though one region may receive more snow than normal in a given year, that doesn’t mean global warming is a farce. Individual weather events viewed in isolation cannot prove or disprove global warming; long term, historical data, on the other hand, is the key to understanding the complex systems that create weather on our planet.


1. Cooney, C. M. (2010, November 1). The Perception Factor: Climate Change Gets Personal. Retrieved November 1, 2010, from Environmental Health Perspectives:
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