Climate change may be a change in weather conditions, or in the distribution of weather around the average conditions. Climate change is an important and long-lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. Climate change may be a change in weather conditions, or in the distribution of weather around the average conditions. Climate change is generally 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 a significant cause of climate change, which is often referred to as ""global warming"".
The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information. The impact factor of a journal is evaluated by dividing the number of current year citations to the source items published in that journal during the previous two years.