Climate changeis a change in the statistical distribution ofpatterns 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 asbioticprocesses, variations insolar radiationreceived by Earth,plate tectonics, andvolcanic eruptions. Certain human activities have also been identified as significant causes of recent climate change, often referred to as "global warmingScientists actively work to understand past and future climate by using<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 fromtemperature profiles,cores removed from deep accumulations of iceperiglacialprocesses, stable-isotope and other analyses of sediment layers, and records of past sea levels. More recent data are provided by the instrumental record., based on thephysical sciences, are often used in theoretical approaches to match past climate data, make future projections, and link causes and effects in climate change.