Climate change refers to long-term changes in the earth's weather patterns. It can occur as a result of natural causes, such as volcanic eruptions, changes in ocean currents, solar variations and changes in orbit. It can also result from human activity, and has been occurring at an increasing rate over the past several hundred years particularly due to the steady increase in carbon dioxide (up by nearly half since the start of the industrial era) and other greenhouse gases in the atmosphere as a consequence of large-scale burning of fossil fuels and widespread deforestation.
The result has been a gradual rise in average temperatures, accompanied by the increased severity and frequency of storms, heat waves and wildfires as well as by the melting of glaciers and the permafrost, rising sea levels, acidification of the oceans and an accelerating extinction of plant and animal species. Among the effects on humans are more extreme weather, disruptions of food supplies, increased disease and the loss of coastal lands.