BLOG POST 4: M Dale Streigle - Greenhouse Gases, Feedbacks and Scenarios

Scientists have know for many years that particular gases in Earth's atmosphere help retain heat at Earth's surface.  If we had no greenhouse gases in the atmosphere, Earth would be very cold.  It has been projected that with no greenhouse effect, Earth's average surface temperature would be about 0 degrees F.   (http://www.giss.nasa.gov/research/briefs/ma_01/).  Of concern is that the modern, industrialized world is pumping such copious quantities of greenhouse gases into the atmosphere that humans are driving climate change (http://www.global-greenhouse-warming.com/).  The accompanying website shows how much three greenhouse gases (carbon dioxide, methane and nitrous oxide) have risen since the industrial revolution (http://www.acs.org/content/acs/en/climatescience/greenhousegases/industrialrevolution.html).  It seems very reasonable to state that as greenhouse gases increase, the climate will trend toward warmer average weather.

About half-way down the page on the U.S. Environmental Protection Agency's website (http://www.epa.gov/climatechange/science/future.html) is a link to a pop-up which does a nice job of answering the question, "How can the use of climate models help in the understanding of these uncertainties" (regarding the effects of climate feedback).  By going to the EPA side and clicking on the image (as seen below) one can work through and increase your understanding of how how such climate models help.  Working through the topics and slides helps understand that complex mathematics are used to project possibilities of what might occur.  This pop-up explains how the mathematical models are tested under current climate conditions, takes steps to explore past changes in climate, and discusses concerns for the future.  In its final slide, the pop-up suggests that with an informed citizenry, we can develop and adopt practices which help mitigates the scale of climate change, and might help us adapt to living in a future, warmer world.

 
Regarding the emission scenarios, I think it likely that the A1FI scenario will play out.  In that scenario, the world's population continues to increase and relies even more on fossil fuels for energy (http://www.epa.gov/climatechange/science/future.html).  As much as advocates for alternative energy would like us to change, barriers are continuously placed in the way of energy sources such as nuclear power.  Wind projects, while touted as clean, are also blocked by people who believe they would spoil their view.  Cape Wind, off of Cape Cod, is gradually gaining steam, but was blocked by quite some time by politicians who felt its development would spoil their ocean view (http://www.capewind.org/index.php).

As shown in the graphic to the right, the highest levels of atmospheric carbon dioxide are achieved in the A1FI scenario (http://www.epa.gov/climatechange/science/future.html).  Temperatures will continue to rise, as increased levels of greenhouse gases enact climate forcings based on the ability of the greenhouse gases to retain heat.  As Earth gets warmer, more evaporation will occur from the oceans, lakes and streams which result in much more water vapor in the atmosphere.  This is a feedback event which causes temperatures to increase even more rapidly and temperatures to rise to even higher levels.  Water vapor is a very powerful greenhouse gas, and enhances the effect of carbon dioxide in the atmosphere.  The graphic below projects Earth's temperatures in the years to come.