background

Background Information

Is Climate Changing?

According to the Global Change Research Act of 1990, global change is defined as "changes in the global environment that may alter the capacity of the Earth to sustain life." Scientists study carbon dioxide (CO₂) and other greenhouse gases when studying global temperatures because similar trends have been found in the changes of gas levels and global temperatures. When comparing the history of global average temperature with the history of carbon dioxide concentration, temperature changes over the last 150,000 years have nearly mirrored changes in atmospheric carbon dioxide concentration. Scientists disagree whether or not anthropogenic (human) activity contributes to climate change. The current warming trend may be natural. As scientist collect more and more data, the link between climate change and levels of greenhouse gases is becoming more evident.

To determine what the concentration of greenhouse gases were in ancient time, scientists have measured tree rings, lake and ocean sediments, and samples of air trapped in glacial ice from several places around the earth. Atmospheric greenhouse gas data from an ice core obtained at the Antarctic Vostok station show the relationship of CO₂ and temperature back 150,000 years. When the amount of CO₂ increased so did the temperature, when it decreased, temperature decreased. More recently, levels of CO₂ have been collected at the NOAA Mauna Loa observatory in Hawaii since the mid-1950's.

How do we get from what we know now about rising CO₂ levels and temperature to future predictions?

Since scientist can't design experiments with the climate system to test their ideas, complex computer models have been developed to help predict climate changes and their effects. The atmosphere, the oceans, land surfaces, the cryosphere, and biosphere interact in very complex ways so it is difficult to determine what are the causes and the effects of climate change or to predict future changes. When climate begins to change, other factors called "feedbacks" also start to change. Clouds, water vapor, plant growth, polar ice sheets, ocean circulation, ocean ecology, terrestrial ecology, and reflectants produce positive and negative feedbacks. These complex climatic feedback processes can slow the rate or increase the rate of climatic changes or rising CO₂ level. Future climate projections by computer models do not account for all of the interaction of the feedback processes. Without incorporating the feedbacks into current climate models, making an accurate prediction becomes nearly impossible.

Scientist are working to improve their understanding of how much carbon is stored in and exchanged among oceanic, atmospheric, and terrestrial reservoirs and incorporate the feedback loops into computer models. Since global climate change is so complex and has the potential for sever impacts, collaboration between scientific research and policies is important. Because global warming is not projected to change uniformly world wide, regional policy makers will need to analyze the potential impact of climate change and develop strategies to minimize the economic, social, and ecological consequences.

References:

Hartman, D. (1997). Reports to the Nation on our changing Planet: Our Changing climate. University Corp. for Atmospheric Research pursuant to National Oceanic and Atmospheric administration Award No. NA57GPO576.

HOME

Woodrow Wilson Leadership Program in Environmental Science

lpt@www.woodrow.org
The Woodrow Wilson National Fellowship Foundation

webmaster@woodrow.org
CN 5281, Princeton NJ 08543-5281

Tel:(609)452-7007

Fax:(609)452-0066