Climate Change

Video Transcription

Hi, I'm Jensen Morgan. We're going to talk about some great concepts in environmental science. Today's topic is climate change. So let's get started.

We're going to talk about the Earth's climate and how it is changing. Scientists observations from year to year are consistently supporting theories of global warming and climate change. A prime observation is the records of global land and ocean temperatures since 1880, as shown in this graph. You can see that overall there has been a significant rise in global temperature.

Another example is the melting and shrinking of glaciers and ice caps as a result of global temperature rise. This is a prominent glacier in Iceland with a large lake at its base in 1977. By 2004, it had receded quite a bit. You can see more of the rock outcropping present on the right, and the lake at its base was 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.

Another clue to climate change and global temperature rise is the rise in sea level worldwide. As the planet heats up, its ice caps and glaciers-- as we saw in the previous slide-- are melting. The result is that more fresh water is joining the seawater in our oceans and the average sea level is rising. Since 1880, sea levels have risen almost 20 centimeters worldwide.

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 the 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 average global temperature will continue to rise somewhere between 2 and 1/2 to 10 degrees over the next 100 years. Where we fall in that range will mostly depend on human activities and choices. To give you context for the range a few degrees of change can cause, think about this-- at the end of the last Ice Age, the entire United States was covered in thousands of feet of ice, yet the average global temperature was only five degrees colder than it is now.

The earth's climate is determined by energy from the sun, amount of land cover versus water cover, the amount of cloud cover or atmospheric moisture present, the thickness of our ozone layer, and atmospheric concentrations of greenhouse gases and aerosols. In the past, climate change was caused by changes in the amount of energy from the sun hitting Earth as 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 of the Earth and reflects it back towards the atmosphere in the form of heat, instead of letting the radiation reflect into space. This results in general atmospheric warming. Greenhouse gases got their name because this process is very similar to the function of a greenhouse used for growing plants.

Our atmosphere is made up of 78% nitrogen, 21% oxygen, 0.93% argon, 0.03% carbon dioxide, and 0.07% of 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. Yet it is not the most potent of greenhouse gases, despite the rap it gets. 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.

Now let's have a recap. We talked about the Earth's climate, observations supporting climate change, and how our climate and atmosphere function in relation to climate change. Well, that's all for today. I look forward to next time. Bye.