noun [klahy-mit cheynj]
  1. a long-term change in the earth's climate, especially a change due to an increase in the average atmospheric temperature.
  2. a result of global warming, with immediate and significant risks to the world.
  3. caused, in part, by human-generated emissions of greenhouse gases.


When energy from the sun enters the atmosphere, some of it warms the earth's surface while the excess is bounced back into space. Greenhouse gases (gases in the earth's atmosphere that trap solar radiation) play a role in this process by trapping energy and preventing it from reflecting back into space.

As a natural process, greenhouse gases are not bad. If they did not trap some of the sun's energy, the earth's average temperature would never have warmed up enough to support life. However, a build-up a greenhouse gases traps enough heat to warm up the earth in a process called global warming.

It is critical to the earth's health that the amounts and types of gases in our atmosphere remain in a balanced state. A proper balance ensures a resilient carbon cycle with a natural ebb and flow among all of our earth's systems. The total amount of carbon in the earth's system remains constant, and it flows along pathways between the earth's major carbon reservoirs - the biosphere (soil, freshwater, and living things), the atmosphere, oceans, and geological sediments (including deposits of fossil fuels like coal and oil).
However, recent human activities have thrown these cycles out of balance; there are too many greenhouse gases in the atmosphere. These gases are holding in too much heat and disrupting the carbon cycle. Global warming and a disrupted carbon cycle lead to climate change.


When the climate warms, the weather changes; the earth's average temperature is rising. A warmer earth is generally less able to regulate temperature shifts, so weather patterns become more extreme. In the Midwest United States, average temperatures are expected to rise an average of 3 degrees by 2100, with heat wave spikes as high as 10-20 degrees above normal during the summer. The relationship between climate change and tornados are not fully understood, but scientists suspect that a warmer atmosphere will increase the intensity of tornadoes.

A warmer atmosphere intensifies and disrupts precipitation patterns, resulting in extreme weather such as drought cycles, intensified flooding, and unseasonable precipitation. Most climate models projects episodes of extreme drought in the Midwest, coupled with an increase in humidity and a decline in surface water.

Climate change impacts the amounts and types of crops that are able to grow - some things will grow more, some less, some not at all, and some will grow where they never could before. Warmer temperatures increase weeds, insects, and pathogens, increasing the challenges facing crop-growers. Livestock, too, will suffer in higher temperatures and a potential decrease in available grazing land.

Increase pressure on agricultural land to meet food and energy needs will likely compromise conservation, habitat protection and wildlife populations. Species within a given ecosystem--including plants, animals, and microorganisms--will need to adapt to a changing climate. Some species will disappear, while others will colonize new territories.

Economic and Social
As the climate changes, human culture will inevitably change as well. Historical events, like the Midwest's Dust Bowl in the 1930's demonstrate that climate shifts, coupled with economic and agricultural factors, can lead to long-lasting natural disasters. More recently, Hurricanes Katrina and Rita have shown how flooding can cause major problems. On a more global scale, it should be noted that two-thirds of the world's population (mostly in poor and developing countries) lives near a coast line and is at high risk of economic and social problems resulting from rising sea levels and increased flooding.


Climate scientists study the earth’s climate and gather data that is studied over broad scales of time. This scientific data informs most of what we know about climate change.

This is the study of the earth's previous climates, based on samples taken from ice cores, ocean sediments, tree rings, coral reefs, and other locations. These sources provide historical records, revealing amounts of greenhouse gases in the atmosphere and extended periods of heating and cooling. As paleoclimatologists understand how forces of climate change worked in the past, they are able to apply these principles to the present and future.

Climate Models
Climate models are complex computer simulators that project (not predict) future climate shifts based on a large range of factors, including energy transfers, land use patterns, fluctuation in atmosphere, polar ice, oceans and land mass, precipitation patterns, and carbon sinks. Current models estimate that the global temperature could rise 4-7 degree Fahrenheit during the 21st century.

Standards of Certainty
By its very nature, science is constantly evolving. Scientists remain committed to the spirit of inquiry, and as result, certainty is usually not a part of their vocabulary. But the 2007 Report of the Intergovernmental Panel on Climate Change used unequivocal language in stating that it is "virtually certain" that climate change is now happening at an unprecedented rate, and that humans are a big part of the problem.


While scientists are virtually certain that our climate is changing, they are not certain how much it will change, how fast or how slow the changes will happen, or what the exact effects will be. Scientists continue to develop better regional and local climate models.

Even without a complete understanding of the details of climate change, the trends are unmistakable. That is why it is important that we take steps today to reduce and manage the effects of climate change, even as we learn to adapt to the potential risks of the changes already underway.

We can fight climate change by:
  • Lowering human-generated greenhouse gas emission
  • Eliminating our dependence of fossil fuels
  • Developing renewable energy
  • Becoming more energy efficient
  • Using land and natural resources in a sustainable manner
  • Consuming less energy in the first place