Thursday, May 28 - Earth - Climate Change

Objective: Understand how climate change impacts life on Earth.

The Earth’s temperature has to stay in a range in which organisms can live – not too hot, not too cold. Earth temperature is balanced by the heating of the surface from sunlight and the insulating and warming properties of the atmosphere.

The sun is the source of most of the energy on Earth. About 30 percent of the energy from the sun is reflected back into space by the atmosphere, the clouds and the Earth’s surface. About half of solar energy is absorbed by the Earth’s surface and the remaining 20 percent is absorbed by the atmosphere and the clouds.

There is a balance between the amount of solar radiation absorbed by the Earth’s surface and the amount sent back into space – it’s called the radiation balance (the balance between incoming radiation and outgoing heat). Over a year, the amount of energy Earth loses to space is about the same as what it receives from the sun. To keep the planet livable, the balance needs to stay equal.

So, the Earth’s surface absorbs about 50% of solar radiation, then radiates a portion of the energy out as thermal radiation. Greenhouse gases such as carbon dioxide and methane absorb some of that radiation by transforming it into energy. The greenhouse gases emit energy in all directions – some escapes into space some is absorbed and some warms the Earth. Without greenhouse gases, the Earth’s temperature would be much colder, but as more greenhouse gases are released into the atmosphere by pollution, scientists are concerned about the world becoming too hot.

The energy from the sun does not heat the Earth evenly. The uneven distribution of energy sets in motion currents that cause weather. Weather distributes energy throughout the atmosphere through the movement of air and water (wind).

Burning fossil fuels is associated with climate change. Fossil fuels store carbon and when they are burned, carbon dioxide is released into the atmosphere. Atmospheric carbon dioxide helps moderate temperatures on Earth. An increase in carbon dioxide increases the greenhouse effect and causes the Earth’s temperatures to rise. Measurements show the amount of carbon dioxide in the Earth’s atmosphere has increased 28% in the last 100 years. At our current rate, it could rise another 40% by the end of the 21st century. Consequences of climate change include the melting of glacial ice and a rise in sea level.