Global Temperature
The earth is naturally warmed by rays (or radiation) from the sun which pass through the earth's atmosphere and are reflected back out to space again.
The atmosphere's made up of layers of gases, some of which are called 'greenhouse gases'. They're mostly natural and make up a kind of thermal blanket over the earth.
This lets some of the rays back out of the atmosphere, keeping the earth at the right temperature for animals, plants and humans to survive (60°F/16°C).
So some global warming is good. But if extra greenhouse gases are made, the thermal blanket gets thicker and too much heat is kept in the earth's atmosphere. That's when global warming's bad.
Global Climate
Temperature is a major part of climate. Temperature controls many things, including the availability of water. In fact, a temperature increase of 5 to10 °F (3 to 6 °C) in the United States could result in a decrease in soil moisture of 10 to 30 percent during the summer. A decrease in soil moisture could cause natural vegetation and crops to dry out. This could severely impact the environment as well as the economy.
Scientists estimate that mean global temperatures have increased by 0.5 to 1.0 °F (0.3 to 0.6 °C) in the last 100 years. Note that this is an increase in the "mean global" temperature. "Mean global temperature" refers to the average of all of the temperature changes from throughout the world.
In reality, the temperature change has not been consistent across the planet. In fact, the temperature change has not been consistent across the United States (see map below). In the last 50 years, temperatures in the western United States have warmed. At the same time, temperatures in the eastern United States have cooled. The cooling in the southeastern United States may be due to excessive sulfates in the air. Sulfates can scatter the sun's light before it reaches the earth's surface. Without heat from the sun, the earth's surface will cool.
What is Climate Change?
EarthImagine our planet. It has a delicate atmosphere – much like a blanket – which protects us, makes us comfortable and able to sustain life.
Climate change has occurred because this blanket has started getting thicker. This has meant our climate is getting hotter and will make it harder for us to live in comfortably.
This will happen because much higher levels of CO2, and other greenhouse gases, have been emitted. This is because CO2 and other gases are emitted when we burn any fossil fuels to generate energy, or when we chop down forests (trees absorb CO2, so this CO2 is released when they are cut down). Our climate is changing.
When people talk about the ‘climate’, it usually refers to the long term weather we experience. When the climate changes, the day to day weather we experience will subsequently change also.
The climate has changed a number of times since earth’s existence over millions of years. However, climate change now refers to the shifts in temperature over approximately the last 100 years, and the next 100 years or so.
There is very strong evidence and almost unanimous agreement amongst the science world that significant global warming is occurring, and that warming in recent times is mostly due to human activities. Therefore, the causes of climate change are:
Natural causes – There are certainly some changes to the earth’s climate caused by interactions between the sun, land, oceans and atmosphere. These tend to occur over very long periods of time.
Human causes – Human activities over thousands of years have changed the concentration of greenhouse gases in our atmosphere in two ways. Firstly, burning fossil fuels such as coal, oil and gas to generate energy releases greenhouse gases. If you imagine how much energy businesses, industry and we as individuals use – that’s a lot of greenhouse gas generated. Secondly, trees are extremely important as they absorb carbon dioxide – the very gas we’re trying to get rid of – so where we start chopping trees down, more carbon dioxide is emitted into the atmosphere.
