Questions for the Glacier Above Town

Watching Larkspur Glacier

1Silver Pass is a small town high in the Rocky Mountains. Above the town lies Larkspur Glacier, a thick body of ice that creeps slowly down the valley. The town museum has photos of the glacier taken from 1910 to today. The town's Hazards Office keeps records of earthquakes and landslides, because the steep slopes above the houses can slide. This year, the office asked the middle school's Glacier Watch club to help write questions for a team of climate scientists who will visit in the summer.

2Club members Pema Dorjee and Rowan Whitehorse collected the records in Table 1. Earth's average surface temperature has risen by about 1 °C since the late 1800s, and most mountain glaciers around the world have shrunk during that time. Scientists study several factors that can change Earth's temperature.

3Some factors are natural. The energy given off by the Sun rises and falls slightly in a cycle that lasts about 11 years. A large volcanic eruption can send tiny particles high into the air, where they reflect sunlight and can cool Earth for a year or two. Slow changes in Earth's orbit can change the climate, but they take tens of thousands of years. Other factors come from human activities. Burning coal, oil and natural gas releases carbon dioxide (CO₂). Clearing forests leaves fewer trees to take in CO₂, and livestock and landfills give off methane. CO₂ and methane are greenhouse gases: they absorb energy given off by Earth's surface and send some of it back down.

4Some factors act only in one place. Dark dust and soot that settle on snow can make it absorb more sunlight and melt earlier in spring. In 1983, an earthquake shook the valley and set off two landslides. Some residents wonder whether the shaking cracked the glacier and made it shrink.

5The scientists sent the club one tip: a good science question can be answered with measurements, and it says what will be measured or compared.