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range K. reproduced L. kind M. sounds N. within O. However The warming of the Earth observed over the last 100 years is due to a combination of many factors. Warming due to the increase in greenhouse gases _______ (1) has been the determining factor so far. _______ (2), projections of greenhouse warming do not rest on recent observations; they come from scientific understanding of the climate system. A _______ (3) of simple and complex computer models has been used over the last 30 years to put together knowledge of many climate processes. Contrary to some scientific opinion, current models do a reasonable job of simulating today’s climate. The difference between summer and winter temperatures, in _______ (4) to change in heating from the Sun, is correctly simulated to _______ (5) about 0.5 degrees over much of the planet. Natural events provide additional tests of our understanding. For example, the scale and _______ (6) of cooling due to the eruption of Mt. Pinatubo were _______ (7) by climate models. When greenhouse gases are increased in climate models, the response is always an increase in average temperatures and water vapor. Models vary in their results but, in virtually all cases, doubling the amount of carbon dioxide increases global average temperatures _______ (8) between 1.5 Celsius Degrees and 4 Celsius Degrees. Why are there some dissenting _______ (9) heard on the science of climate change? _______ (10) it appears that critics are simply unaware of the depth of the science developed so far. Others are concerned because we do not understand everything about the climate system.