BLOG POST 3: M. Dale Streigle - Climate Forcings and Feedbacks

1) Regarding the question of "Which climate forcings and feedbacks are most prevalent in either your local area or in the United States as a whole and why might this be so?", I will address the issue pertaining to Las Vegas in particular and Nevada in general.

Over the years, development has greatly altered the surface of the Las Vegas basin from natural to artificial.  In so doing, the albedo has been drastically affected.  As per the interactive "Earth's Albedo and Global Warming" (http://www.pbs.org/teacherline/courselinks/x7warq/), surfaces with high albedos reflect much insolation (as visible light) back towards outer space while surfaces with low albedos absorb much insolation, changing the energy of visible light to the longer wavelength infrared light (heat).  The original surface of the Vegas area was light-colored, dry soil.  This has largely been replaced by concrete and asphalt, hundreds of thousands of buildings with roofs darker than the original soil, and scattered golf courses and swimming pools.

As shown in this table of albedos of different materials (http://ecosystems.wcp.muohio.edu/studentresearch/climatechange03/snowball/web%20page/images/Albedo%20Chart.jpg), the original, light-colored dry soil of the region reflected up to 45% of incoming solar radiation (insolation).  Between the asphalt and darker colored concrete and roofs, and considering the absorptive effects of water in pools, only from 3% to 15% of insolation is reflected.  Consequently, the altered surface is a forcing which causes the Vegas area to have higher temperatures than normal.  Development is not slowing down.  As development encroaches further into the surrounding desert, we can expect our temperatures to get even hotter.


The Center for Integrative Environmental Research released a report in 2008 titled Economic Impacts of Climate Change in Nevada (http://www.cier.umd.edu/climateadaptation/Nevada%20Economic%20Impacts%20of%20Climate%20Change.pdf).  In this article, the authors discuss that, "In the last century Nevada has experienced a slight increase in temperature, increased precipitation, a shortening of the snow season, and increased storms in general (USGCRP 2000). A .5°F increase over the last 100 years has resulted in more heat waves and more aridity (EPA 1998)."  Regarding future impacts of climate change in Nevada, the authors state, "By 2100, the average temperatures for Nevada are expected to increase by 3-4°F in the spring and fall and by 5-6°F in the summer and winter (EPA report 1998). El  Niño also is predicted to increase in frequency and duration as a result of global climate change (Trenberth and Hoar 1997). Increasing temperatures will affect the rate of water evaporation and precipitation in the state. Precipitation will become increasingly erratic in the coming century with decreases expected in the summer months of about 10 percent and potential increases of 15-40 percent in the fall, spring, and winter months (EPA Nevada Report, 1998). In general, Nevada is expected to have wetter winters and more arid summers as the subtropical dry zones for the whole planet are projected to increase (USGCRP 2000; Fang Ting, Science). Higher temperatures and increased winter rainfall will be accompanied by a reduction in snow pack, earlier snowmelts, and increased runoff. (IPP Regional projections report 2008)."

Levels at Lake Mead are already at historically low ranges.  This is a serious problem for a region which relies on drawing water from Lake Mead for all our daily needs.  The Southern Nevada Water Authority (SNWA http://www.snwa.com/) wants to build a multi-billion dollar water pipeline to counties in northern Nevada through which they advocate pumping water siphoned from their resources.  Northern Nevada is an agricultural area of the state, and is greatly concerned they will lose the water vital to maintaining livestock and crops.  The SNWA has expressed their belief that the water needs of Las Vegas (a community which has no compunction regarding the extraordinary quantities of water needed to maintain a myriad of golf courses -- and which still permits the construction of new golf courses) represent a greater "right" to the waters of northern Nevada than any "right" possessed by the residents of northern Nevada.  "Assurances" have been given by the SNWA that northern Nevadans would have water enough left to meet their needs (needs being defined by SNWA).

2) Concerning the question of, "What resources have you located to help you and your students understand climate forcings and feedbacks?", the many resources offered in the readings of Session 2 are likely to prove invaluable.  There are 22 resources alone found within the resources listed as the ESSEA (Earth System Science Education Alliance) NASA Global Climate Change Education Modules website (http://essea.strategies.org/module.nasa.html).  The ESSEA site also offered problem-based learning strategies to utilize in our classrooms (http://essea.strategies.org/inquiry.html).  I'm certain I will be able to incorporate ideas from their list to help my students understand the concept of climate forcings and feedbacks.