An overwhelming body of scientific evidence paints a clear picture: climate change is happening; it is a caused in large part by human activity and it will have many serious and potentially damaging effects in the decades ahead. Scientists have confirmed that the greenhouse gas emissions from cars, power plants and other manmade sources—rather than natural variations in climate—are a primary cause. (Do read on, but when you are done, don't feel down—feel good by starting to enroll your school today!)
The Earth's climate has changed many times during the planet's history, with events ranging from ice ages to long periods of warmth. Historically, natural factors such as volcanic eruptions, changes in the Earth's orbit, and the amount of energy released from the Sun have affected the Earth's climate. Beginning late in the 18th century, human activities associated with the Industrial Revolution have also changed the composition of the atmosphere, and today increased human activity is influencing the Earth's climate in such a way that scientists are calling for dramatic changes in our energy use and consumption.
For over the past 200 years, the burning of fossil fuels, such as coal and oil, and deforestation have caused the concentrations of heat-trapping "greenhouse gases" to increase significantly in our atmosphere. Carbon dioxide (CO2) is the most prevalent greenhouse gas. Greenhouse gases prevent heat from escaping to space, somewhat like the glass panels of a greenhouse.
Naturally occurring greenhouse gases are necessary to life as we know it, because without them, the planet's surface would be frigid and too cold for human life. But, as the concentrations of these gases continue to rapidly increase in the atmosphere, the Earth's temperature is climbing above past levels. According to NOAA (National Oceanic and Atmospheric Administration) and NASA data, the Earth's average surface temperature has increased by about 1.2 to 1.4F in the last 100 years. The eight warmest years on record (since 1850) have all occurred since 1998, with the warmest year being 2005. Most of the warming in recent decades is the result of human activities. Other aspects of the climate are also changing such as rainfall patterns, snow and ice cover, and sea level.
If greenhouse gases continue to increase, climate models predict that the average temperature at the Earth's surface could increase from 3.2 to 7.2F above 1990 levels by the end of this century. Scientists are certain that human activities are changing the composition of the atmosphere, and that increasing the concentration of greenhouse gases will change the planet's climate. But they are not sure about how much it will change, at what rate it will change, or what the exact effects will be.
Whether or not dramatic changes will come next year, in ten years or in one hundred, we believe the best thing we can do is to put into effect an "insurance policy" against the threat of climate change for all of earth's inhabitants. By conserving energy and decreasing our carbon emissions today, we can leave our planet in the same relative condition it has been in for present and future generations to enjoy.