Earth/NOAA A Note on Climate Change

The topic of climate change is complex and often confusing even to experts. As we explore how human activities impact the climate system --and how that in turn will impact human societies-- it is important for us to have a firm understanding of the basic processes and dynamics of the weather and climate continuum. In other words, before we can understand climate change, we need to know what climate is.

If weather is what determines what clothes we wear outside on a given day, climate is what determines what plants we grow and when we plant them. Climate ranges from seasonal changes caused by the tilt of the Earth's axis to long-term processes that occur over millennia. Never static, climate is always changing, sometimes slowly, over thousands or millions of years, sometimes abruptly, over the span of years or decades.

The term "climate change," which has largely replaced the concept of "global warming" in recent years in the United States,* is defined by NASA's glossary as "a significant change from one climatic condition to another.." and "includes natural changes in climate." However, the United Nations defines the term as "a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods."

No matter how the phrase is defined, there is widespread agreement within the scientific community that human activities are in fact impacting the climate system, both through changes in land cover and in the release of carbon from the burning of stored solar energy, i.e. fossil fuels (see below). Before examining what many climate scientists refer to as "anthropogenic forcing" on climate and its projected regional, health and societal impacts, the Climate Change Collection focuses on resources that explore the differences between weather and climate, the dynamics of the greenhouse effect, and the sun's role in the Earth's energy balance.

This collection is funded through NSF Grant EAR-0435645

*According to the Director of the Climate Change Science Program, James Mahoney, the term "climate change" is a more encompassing and technically accurate term to describe the changes in earth systems," than "global warming", which, according to Mahoney, "is an oversimplification, and by definition does not allow for the occurrence of warming in one region and simultaneous cooling or stability in others." William Safire, in the August 14, 2005 issue of the New York Times Magazine, notes: "In the nomenclature struggle, who names an issue usually carries the day. Lexicographers and usagists take no sides, but in common parlance as reflected by the search engines, the neutral climate change has put a chill into the scarier global warming."