One characteristic of physical existence is that change will occur. As time moves forward, change will occur. The only way to halt change is to halt time. Global temperature changes just like anything else in physical existence. The most dramatic changes to Earth’s climate occur over thousands and tens of thousands of years such as ice ages and interglacial periods. Significant changes to Earth’s climate can occur due to volcanic activity, solar output and the orientation of continents. The most controversial aspect of global temperature change is the answer to the question: How much change would happen naturally and how much change is directly attributed to human activity?

Global temperature has risen about a degree Fahrenheit over the last century. The increase has been most significant over land and in polar regions. It is possible at least some of this increase could be due to higher emissions of CO2 (Carbon Dioxide) which is a greenhouse gas that traps longwave radiation. This is the primary factor that is cited for the human influence on warming the climate.

One troubling aspect in trying to determine the exact amount of warming of the last century deals with changing technology, population/building patterns and temperature uncertainty. Instruments that measure temperature have been improved over time. Readings have increased in accuracy over time. Temperature readings such as before 1950 did not have the accuracy of today’s temperature sensors. The increase in construction can cause warmer temperature through the urban heat island. Temperature stations that were once in rural areas are now in urban areas. Urban areas tend to retain more heat and thus will contribute to an indication of a warming climate over time. Measurement errors and human errors are always a concern with measuring temperature and developing temperature sensors.

Even with the factors mentioned in the previous paragraph taken into consideration, there is strong evidence the Earth’s climate has warmed. Examples of evidence for this include the polar ice area tending to decrease in size over the last several decades, retreat of the majority of glaciers, first freezes tending to occur later and last freezes tending to occur earlier, plant and animal migrations to more northerly regions, and sea level rise. Monitoring climate change and determining the factors responsible for it is an area of continuing research.