|
Climate change is a change in the statistical distribution of weather patterns when that change lasts for an extended period of time (i.e., decades to millions of years). Climate change may refer to a change in average weather conditions, or in the time variation of weather around longer-term average conditions (i.e., more or fewer extreme weather events). Climate change is caused by factors such as biotic processes, variations in solar radiation received by Earth, plate tectonics, and volcanic eruptions. Certain human activities have also been identified as significant causes of recent climate change, often referred to as "global warming".〔 〕 Scientists actively work to understand past and future climate by using observations and theoretical models. A climate record—extending deep into the Earth's past—has been assembled, and continues to be built up, based on geological evidence from borehole temperature profiles, cores removed from deep accumulations of ice, floral and faunal records, glacial and periglacial processes, stable-isotope and other analyses of sediment layers, and records of past sea levels. More recent data are provided by the instrumental record. General circulation models, based on the physical sciences, are often used in theoretical approaches to match past climate data, make future projections, and link causes and effects in climate change. ==Terminology== The most general definition of ''climate change'' is a change in the statistical properties (principally its mean and spread)〔()〕 of the climate system when considered over long periods of time, regardless of cause.〔(【引用サイトリンク】work=Education Center – Arctic Climatology and Meteorology ); (Glossary ), in .〕 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.〔(【引用サイトリンク】date=21 March 1994 )〕 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.〔(【引用サイトリンク】url=http://www.nasa.gov/topics/earth/features/climate_by_any_other_name.html )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「climate change」の詳細全文を読む スポンサード リンク
|