Image Credit: Climate scientists are becoming more vocal about the idea that Earth might become noticeably warmer in this century due to the greenhouse effect.
Carbon dioxide is a greenhouse gas. So are methane and water vapor. Greenhouse gas molecules all have three or more atoms, and this complex structure gives them their ability to absorb heat. They let the sun’s light pass through the atmosphere to Earth’s surface. They then reabsorb heat from Earth’s surface. People have used the analogy of a greenhouse trapping heat to describe how Earth’s surface and lower atmosphere might warm.
Greenhouse gases have been increasing since humans began burning fossil fuels over a century ago. Carbon dioxide makes up less than one percent of the atmosphere – but it’s such an important gas that scientists carefully track how much there is in the air. The increase in carbon dioxide is well established. It’s been measured since the 1950s from the Mauna Loa Observatory in Hawaii, under the auspices of the National Oceanic and Atmospheric Adminstration (NOAA).
In 2001, an international panel of climate experts released a report on climate change. Using several different computer models, they predicted that Earth’s surface might warm by anywhere from one-and-a-half to six degrees Celsius in this century, largely because of increases in greenhouse gases.
Scientists now believe that greenhouse gases have all been increasing in Earth’s atmosphere since the start of the Industrial Revolution – over a century ago – due to humans burning fossil fuels. A study of ice cores drilled in Antarctica went back more than 400,000 years – and didn’t find any period in all that time where greenhouse gases were as high as they are today.
Climate scientists predict that a century from now, atmospheric levels of one greenhouse gas – carbon dioxide – will be twice as high as levels naturally occurring in the air before the Industrial Revolution began.
Earth’s surface has warmed by about a degree Fahrenheit in the past century. And as greenhouse gases continue to increase, climate scientists say, so will average global temperatures.
Most climate scientists agree that global climate change presently occurring is due in part to emissions of carbon dioxide and other gases. But no one knows for sure what proportion is due to greenhouse gases and how much is due to other natural factors, such as solar activity.
Mauna Loa was originally chosen as a CO2 monitoring site because being isolated in the middle of the Pacific, the air is exceptionally pure. Being high, it is above the inversion layer. There was also already a convenient road to the summit built by the military. The purity is good as long as contamination from local volcanic sources is detected and removed.
Our thanks to:
Dr. Qiang Fu
Associate Professor
University of Washington
Seattle, WA
Dian J. Seidel
NOAA Air Resources Laboratory
Silver Spring, MD
Dr. John R. Christy
Professor and Director
Earth System Science Center, NSSTC
University of Alabama in Huntsville
Huntsville, AL
Dr. Roger Pielke
Senior Professor and State Climatologist
Department Atmospheric Science
Colorado State University
Fort Collins, CO
