Scientists' observations from year to year are consistently supporting theories of global warming and climate change.
|Date||Changes in Glacier in Iceland|
|This is a photograph of a prominent glacier in Iceland with a large lake at its base in 1977.|
|By 2004, it had receded quite a bit. More of the rock outcropping is present on the right, and the lake at its base is shrinking.|
|By 2011, the glacier had begun receding up the hill, leaving large fissures in the rock. The lake at its base had completely dried up.|
The earth naturally cycles between warmer and colder periods of climate. Periodic ice ages are examples of such changes. Climate change itself is a normal process, one that usually lasts thousands of years as it slowly shifts to its new average temperature, thus allowing species to adapt to the shift in temperature.
The significance of the current climate change is the speed at which it is changing. According to current scientific understanding, the recent rise in temperature, about 1.53 degrees over the last 130 years, is the quickest transition in Earth's history. Scientists expect that the average global temperature will continue to rise somewhere between 2.5 to 10 degrees over the next 100 years. Where we fall in that range will mostly depend on human activities and choices.
The earth's climate is determined by:
In the past, climate change was caused by changes in the amount of energy from the sun hitting Earth as the distance and position from the sun changed. However, the current shifting climate is the result of increased concentrations of greenhouse gases in the atmosphere, generated by human activity. This happens because greenhouse gases, like carbon dioxide and methane, absorb radiation from the sun as it bounces off the earth and reflect it back toward the atmosphere in the form of heat, instead of letting the radiation reflect into space. This results in general atmospheric warming.
Our atmosphere is made up of 78% nitrogen, 21% oxygen, 0.93% argon, 0.03% carbon dioxide, and 0.07% other types of gases, such as methane. At the beginning of Earth's life, there were dramatic changes in its atmospheric makeup. In a relatively short period of time, it went from having 0% to 20% oxygen.
Nowadays, even though CO2 and methane make up a minuscule part of the atmosphere, even small changes can have a huge impact. As CO2 concentrations rise, so does global warming. However, it is not the most potent of greenhouse gases, despite its bad reputation. Methane is actually 30 times more potent than CO2 because of its molecular structure. It will be important to manage greenhouse gases in respect to their potency as well as their quantity.