Climate change refers to a change in average weather conditions and patterns (such as temperature, humidity, precipitation, and wind) over a long period of time, typically 30 years or more. The term can be used to describe the climate of a region or be applied to the entire planet. Earth's climate has been changing over the past century—average surface temperatures have been warming along with rising levels of human-produced greenhouse gases in the atmosphere. Warmer average global temperatures and changes in weather patterns can have significant effects on the environment, including rising sea levels, changes in precipitation, and impacts on plant and animal life.

Global climate change can also affect the frequency and severity of extreme weather events, such as heat waves, storms, floods, and droughts. A special report of the Intergovernmental Panel on Climate Change, published in 2012, examined the relationship between climate change and extreme weather and looked at the risks for society. Extreme weather events can have serious environmental, economic, and human impact: they can, for example, alter ecosystems and affect water supplies, agriculture, tourism, and human health.

Scientific observations and experiments with global climate models (GCMs)—complex computer programs—are used to analyze trends in data and to predict changes in the frequency, intensity, and timing of extreme weather events all over the world. According to the panel’s report, it is very likely that there has been an increase in the number of warm days and nights, and that the frequency and/or intensity of heat waves will increase in some areas. Drought conditions will become more intense in some areas. However, in other regions, the warmer temperatures will allow more water vapor to be held in the air, and more moisture will be available to fall as precipitation. So even if there may be an overall decrease in total precipitation in some regions, the proportion of rain from heavy rainfall may increase. A clear trend in the frequency of more intense tropical cyclones has not yet been identified, but scientists have observed a shift in the storm-track patterns. As a result, storms are more likely to strike in areas where they generally did not in the past.

As seen in this video, Navajo Elders have observed evidence of environmental changes consistent with the predictions of scientists. They have noticed that there are more violent storms in the rainy season, snowstorms are more intense, and certain plants can no longer be found. One Elder mentions that the cold is more extreme in the winter than it once was. While that sounds surprising to many, it is important to recognize that the same trends will not be found in all locations. Different regions are experiencing different effects of climate change.

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