Over the past 900,000 years, the atmosphere has expe-rienced climate change as a result of prolonged periods of considerable atmospheric warming and atmospheric cool-ing that led to ice ages(Figure 15. 18).These alternating cycles of freezing and thawing are known as glacial and interglacial(between ice ages)periodsFor roughly 10,000 years, we have had the good for-tune to live in an interglacial period characterized by a airly stable climate based on a generally steady global av-erage surface temperature. This important form of natural capital allowed the human population to grow as agricul ture developed, and later as cities grew. For the past 1,000 years, the average temperature of the atmosphere near the earth's surface has remained fairly stable. But it began to rise during the 19th and 20th centuries when the expand-ing human population cleared large areas of forests and grasslands, which had been removing CO2 from the atmo sphere, and burned fossil fuels at steadily increasing rates, which added CO2 to the atmosphere Most of the recent overall rapid rise in the global aver age atmospheric temperature on land has taken place since 1978(Figure 15. 19). According to the 2014 study on cli-mate change by the American Association for the Advance-ment of Science(AAAS), evidence from numerous scientific