Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average (e.g., more or fewer extreme weather events). Climate change may be limited to a specific region or may occur across the whole Earth.
The most general definition of climate change is a change in the statistical properties of the climate system when considered over long periods of time, regardless of cause. Accordingly, fluctuations over periods shorter than a few decades, such as El Niño, do not represent climate change.
The term sometimes is used to refer specifically to climate change caused by human activity, as opposed to changes in climate that may have resulted as part of Earth's natural processes. In this sense, especially in the context of environmental policy, the term climate change has become synonymous with anthropogenic global warming. Within scientific journals, global warming refers to surface temperature increases while climate change includes global warming and everything else that increasing greenhouse gas levels will affect.
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According the Government Environmental Protection Agency webpage http://www.epa.gov/climatechange/glossary.html#F on the topic: Glossary of climate change terms, factors that can shape climate are called climate forcings or "forcing mechanisms". These include processes such as variations in solar radiation, deviations in the Earth's orbit, mountain-building and continental drift, and changes in greenhouse gas concentrations. There are a variety of climate change feedbacks that can either amplify or diminish the initial forcing. Some parts of the climate system, such as the oceans and ice caps, respond slowly in reaction to climate forcings, while others respond more quickly.1
From NASA Earth Observatory webpage on the topic: "Glossary". http://earthobservatory.nasa.gov/Glossary/index.php?mode=alpha&seg=b&segend=d, stressed that natural changes in the components of earth's climate system and their interactions are the cause of internal climate variability, or "internal forcings." Scientists generally define the five components of earth's climate system to include Atmosphere, hydrosphere, cryosphere, lithosphere (restricted to the surface soils, rocks, and sediments), and biosphere.2
Andrew S. Gale, author of the book: "A Milankovitch scale for Cenomanian time" on his topic Terra Nova emphasized that slight variations in Earth's orbit lead to changes in the seasonal distribution of sunlight reaching the Earth's surface and how it is distributed across the globe. There is very little change to the area-averaged annually averaged sunshine; but there can be strong changes in the geographical and seasonal distribution. The three types of orbital variations are variations in Earth's eccentricity, changes in the tilt angle of Earth's axis of rotation, and precession of Earth's axis. Combined together, these produce Milankovitch cycles which have a large impact on climate and are notable for their correlation to glacial and interglacial periods, their correlation with the advance and retreat of the Sahara, and for their appearance in the stratigraphic record.3
On the broadest scale, the rate at which energy is received from the sun and the rate at which it is lost to space determine the equilibrium temperature and climate of Earth. This energy is distributed around the globe by winds, ocean currents, and other mechanisms to affect the climates of different regions.
Factors that can shape climate are called climate forcings or "forcing mechanisms". These include processes such as variations in solar radiation, deviations in the Earth's orbit, mountain-building and continental drift, and changes in...
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Gale, Andrew S. (1989). "A Milankovitch scale for Cenomanian time". Terra Nova 1 (5): 420. doi:10.1111/j.1365-3121.1989.tb00403.x.
"Glossary". NASA Earth Observatory. 2011. http://earthobservatory.nasa.gov/Glossary/index.php?mode=alpha&seg=b&segend=d. Retrieved 8 July 2011.
Haigh, Joanna D.; Ann R. Winning, Ralf Toumi, Jerald W. Harder (2010-10-07). "An influence of solar spectral variations on radiative forcing of climate". Nature 467 (7316): 696–9. Bibcode 2010Natur.467..696H. doi:10.1038/nature09426. ISSN 0028-0836. PMID 20930841.
Sagan, C.; G. Mullen (1972). Earth and Mars: Evolution of Atmospheres and Surface Temperatures. http://www.sciencemag.org/cgi/content/abstract/177/4043/52?ck=nck.
US EPA. Glossary of climate change terms.
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