This summary of the issues by Brennan Jorgensen explains why we need to do something, NOW:
Since the dawn of the Industrial Revolution, the level of carbon dioxide (CO2) in the
atmosphere has increased 40% after remaining relatively static for hundreds of thousands of years. In fact right now, carbon dioxide levels at 390 ppm are at the highest ever recorded in at least 800,000 years according to air samples retrieved from polar ice cores.
Currently, human activities largely revolving around the combustion of fossil fuels, deforestation, and other activities are emitting CO2 at over 135-times the natural volcanic background rate, according to the U.S. Geological Survey: http://volcanoes.usgs.gov/hazards/gas/climate.php.
Why are carbon emissions such a concern?
Like other greenhouse gases such as water vapor and methane, these molecules have the property of absorbing long wave (heat) radiation that primarily comes from the sun.
When infrared radiation strikes molecules such as carbon dioxide and methane it causes the bonds to bend and vibrate. This is called the absorption of IR energy and the molecule gains kinetic energy.
This extra kinetic energy is then transmitted to other molecules such as oxygen and nitrogen that make up the bulk of the atmosphere and it causes a “greenhouse effect” or warming of the atmosphere. While the largest greenhouse gas, water vapor, has remained relatively constant over the last century both carbon dioxide and methane continue to rise at a rapid pace due to human activities.
What evidence is there that carbon emissions are causing the atmosphere to warm? Direct weather observation has been the most revealing. The National Oceanic and Atmospheric Administration reported that all 11 years of the 21st century so far (2001–2011) rank among the 13 warmest in the 132-year period of weather records even though the single largest source of radiative forcing, incoming solar radiation, has been declining from the sun over the last several decades;
“NASA researchers updated calculations of the Earth’s energy imbalance, which is the
difference between the amount of solar energy absorbed by the Earth’s surface and the amount returned to space as heat. They found that despite unusually low solar activity from 2005 to 2010, the planet continued to absorb more energy (half a watt more per square meter) than it returned to space during that time period.”
That the atmosphere traps half a watt (6/10th to be exact) more energy per square metermay not seem like much to worry about but really is a tremendous amount of heat. According to NASA researchers, it is the equivalent of releasing the energy of some 400,000 Hiroshima atomic bombs every day 365 days a year.
Imagine if a terrorist were found to be releasing the energy equivalent of 400,000 atomic bombs a day into the atmosphere? We would have global national security crises on a magnitude not seen since World War II.
To put this in another perspective, the last greatest episode of geological global warming called the Paleocene-Eocene Thermal Maximum (PETM) lasted 20,000 years and witnessed an estimated global temperature rise upwards of some 6 degrees Celsius during that time interval about 55 million years ago: http://www.sciencedaily.com/releases/2011/06/110605132433.htm
We are now emitting carbon emissions at 10 times the rate of the PETM episode, we are projected to ascend the temperature equivalent of a PETM in just one century which would be catastrophic for civilization in terms unacceptably extreme weather disasters.
Scientists and policy makers have already estimated that any global temperature increase approaching 2 degrees Celsius would be pushing civilization to the brink. This is why it is so important to reduce are carbon emissions now us and the safeguarding of future generations.