Evidence Of Global Warming

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Since the early 1900s, most of the glaciers around the world have been melting and retreating at rates faster than have ever been recorded. Since the beginning of the Industrial Revolution in the mid-1700s, scientists have noted that glaciers, which are extremely responsive to current temperature change, have been receding. Changes will continue to happen as long as the atmosphere continues to heat up. According to the IPCC, "Ample evidence indicates that global warming is causing glaciers to retreat worldwide." Changes can be observed, measured, and monitored in order to determine how fast glaciers are melting and how that impacts humans. Today's technology has also stepped in. Space satellites are now able to measure the global temperature trend. Mass balance of a glacier is calculated (mass added each year compared to mass melted) as cubic meters of water lost, or as thickness averaged over the entire area of the glacier. The findings are sobering. The world's sources of freshwater are being reduced. Areas of the world that depend on melting glaciers for their drinking water are suffering because this natural resource is becoming scarcer. As an example, the Himalayan glaciers feed into seven of the great rivers of Asia and supply year-round water to 2 billion people. In the Ganga (one of the rivers that receives water from the Himalayan glaciers), the loss of glacier meltwater would cause water shortages for 500 million people and for 37 percent of India's irrigated land. Countries in South America are faced with similar situations.

In other areas where glaciers are melting rapidly, flooding is another threat that is being measured. Sometimes huge chunks of glacial ice can fall into lakes and cause glacial lake outburst floods, killing many people. Another consequence that is being measured is sea-level rise. As ice sheets' meltwater enters the ocean, it raises the water level, flooding coastal areas. As more glaciers continue to melt, coastal towns will be flooded and destroyed.

The Arctic, maybe more so than any other place on Earth, has felt the effects of global warming. Its fragile ecosystem is very vulnerable to change. It is especially susceptible to changes in climate. One reason for its fragility is that it is a relatively new ecosystem; up to as recently as 20,000 years ago it was covered by glaciers in the ice age, and the eco system, therefore, did not exist. Weathering is also a very slow process in colder climates, which means that in the Arctic it takes an extraordinary amount of time for soil to form, as compared to the hot, humid tropical areas on Earth. The arctic soil is also very low in nutrients, putting the plants at a disadvantage. Two other conditions plant life has against it are that it must live in conditions of low temperature and low light. The Arctic ecosystems are truly the most extreme conditions found on Earth, and any life that survives must learn to adapt to these extreme conditions. Because of all these disadvantages, Arctic ecosystems have an overall lower productivity compared to other ecosystems. These natural hardships that ecosystems must face in the Arctic also puts hardships on the wildlife that live within the habitat. When situations such as global warming and pollution enter this fragile environment, it can be especially devastating, when compared to other ecosystems, simply because it does not have as much resistance. Change in the Arctic, however, means change everywhere. Because polar areas play an important role in Earth's heat balance, what affects the Arctic, ultimately affects the entire planet.

Scientists have identified several pieces of evidence that global warming is occurring. For example, the 10 warmest years ever recorded all occurred within the past 14 years. Ice cover at both poles is shrinking. The Greenland Ice Sheet has undergone a record amount of melting, and glaciers in Canada and Alaska are disappearing at record rates. The Arctic growing season has lengthened by a few days per decade over the years. Permafrost has started to thaw, causing many problems for inhabitants of those polar areas, as the ground shifts and settles.

If the snow and ice begin melting in the Arctic, they will no longer be able to reflect incoming sunlight, causing the planet eventually to heat up. The Arctic can also cause a rapid global warming if the frozen peat bogs begin thawing and large amounts of carbon dioxide (CO2) are released into the atmosphere.

According to proxy records in ice cores, peat cores, and lake sediments, Arctic air temperatures have risen by 0.8°F (0.5°C) each decade over the past 30 years. Most of this warming has occurred in the winter and spring. In addition to this, atmospheric temperatures from the late

1900s to the present are at their highest level in the past 400 years. Cli-matologists have documented that Arctic and Northern Hemisphere river and lake ice have been forming later and melting earlier over the last few centuries. In fact, since 1850, the total ice-cover season is now 16 days shorter. According to the Yukon Conservation Society, sea ice in the Arctic covers about 10 to 15 percent less area in the spring and summer than it did in the 1950s. The ice is also estimated to be about 40 percent thinner in the late summer and early fall than it was in recent decades. When the darker water around the ice edges starts absorbing heat, the ice at the edges of the open water quickly melts away and the darker area gets bigger. This larger area absorbs more heat. This starts a cycle that soon speeds up. In the Arctic Ocean, as global warming causes warmer temperatures, more ice will melt because the air is warmer. In addition, satellite technology has confirmed that each year the number of snow-free days increases in the Arctic and the growing season extends by a few days.

One of the most obvious pieces of evidence that climatologists have keyed in on is the multitude of shrinking glaciers over the past 50 years. Even more alarming, during the past 10 years, the melting rate has become three times faster than what it was before. In a cause-and-effect relationship, this means that melting glaciers are contributing to sea-level rise. According to the USGS in 1986, there had been a warming at ground level of 3.3 to 6.7°F (2-4°C) during the past few decades. Thawing permafrost is disastrous on developed areas with highways, roads, and other structures. At present, the USGS is actively engaged in research concerning the emission of methane hydrates (a greenhouse gas) from the permafrost layers as it melts. This could contribute significantly to global warming. Currently, they have researchers participating in research projects in Alaska, Canada, and Russia, studying and monitoring environmental impacts and implications. They are also interested in melting sea ice and what impact that is having on global sea rise.

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