The effects of climate change are also projected to impact land use and recreation policies in the park, which will have a subsequent impact on the local economy. Glacier contributes approximately $150 million to Montana's economy each year and supports roughly 3,200 jobs in the state. In addition to Montana, Glacier also generates substantial revenue for neighboring states as well as areas in Canada. As the glaciers continue to retreat and disappear, it is likely that fewer people will

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... to return to the park. Water ton Lakes National Park in Canada conducted a study on the effects of glacier loss and found that 19% of visitors would not return to the park and 37% would return less when given a description of how the park's landscape would be affected by climate change. INTRODUCTION The Earth's climate has exhibited marked "natural" climate changes, with time scales varying from many millions of years down to a few years. Changes in land and ocean floor topography have had major influences on global climate at time scales of 50 million to 150 million years. Over the last two million years the onset and recession of the great Ice Ages were probably influenced by changes in the earth's orbit and the tilt of its axis, which caused systematic variations in the amount and distribution of solar radiation. Global average temperatures varied by about 5-7°C. Since the end of the last ice age (14,000-10,000 years ago) globally averaged surface temperatures have fluctuated over a range of up to 2°C on time scales of centuries or more. Factors influencing these changes probably included fluctuations in the radiation output from the sun, and changes in circulation and overturning in the oceans. Increased amounts of greenhouse gases in the atmosphere will absorb more thermal radiation, and the Earth's surface and the lower atmosphere will warm. This extra warming is called the enhanced greenhouse effect.