The term "climate change" is broadly used though its meaning can vary considerably. Here, it refers to a rise in the average global temperature due to an increase in the concentration of atmospheric greenhouse gases, resulting in numerous climatic shifts and impacts around the globe. There are several gases that exist naturally in the atmosphere and contribute to the warming of the Earth's surface by trapping heat from the sun, also known as the greenhouse effect. However, burning fossil fuels also contributes to the concentration of greenhouse gases, including carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), among others. There is broad scientific consensus that human activities, most notably the burning of fossil fuels for energy, have led to the rapid buildup in atmospheric greenhouse gases. The Intergovernmental Panel on Climate Change (IPCC) stated in 2007 that CO2 levels in the atmosphere rose from a pre-industrial level of 280 parts per million (ppm) to 379 ppm in 2005. This has coincided with an increase in the average global temperature of 0.74 [±0.18]°C / 1.33 [± 0.32]°F between 1906 and 2005.

In its latest report in 2007, the IPCC concluded that the warming of the climate system is unequivocal. Furthermore, the IPCC stated that there is very high confidence (or 90 percent certainty) that human activities since 1750 have had a global average net effect of warming the planet. Impacts from this warming already have been observed and include increases in global average air and ocean temperatures, accelerated melting of snow and sea ice, widespread retreat of glaciers, rising global average sea level, increased ocean acidity, extensive changes in weather patterns, including changes in precipitation levels and increased storm intensity. Climate change is the greatest environmental threat confronting the world.

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