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Hot Nights

Las Vegas nights aren't as cool as they used to be, literally. Nighttime Low temperatures have increased nearly 10 degrees on average over the past 60 years. KNPR's Ky Plaskon reports.

PLASKON: Las Vegas' low temperatures in January from 1940 to 1979 were always below 40-degrees. But since then January temperatures have climbed 16 degrees, and over the same period every month has experienced double-digit temperature increases. Summer lows used to be in the high sixties, now they climb into the 80's.

ASHAY: There has been a definite rise, since the mid 80s and the temperatures are rising quite drastic actually.

PLASKON: Jim Ashay of the Western Regional Climate Center says it's not just part of some cycle, it is a trend in urban areas across the nation, called the Heat Island effect. Rural environments and towns just 30 miles outside of urban areas haven't experienced this same temperature rise he says. The heat islands in Las Vegas and Reno developed during rapid growth in the 80's and the desert was paved over he says.

ASHAY: It doesn't cool off at night because concrete and asphalt retain heat much better than the desert and so it keeps it much warmer at night, it is a heat island downtown.

PLASKON: Daytime high temperatures on the other hand haven't been affected.

SOUND: Concrete Convention

PLASKON: At the World of Concrete Convention this year in Las Vegas, Terry Collins President of the Portland Cement Association agrees concrete is the culprit.

COLLINS: The thermal mass of the concrete, yes, it keeps it a little warmer during the night time, however it keeps it a little cooler during the day because it reflects more solar radiation into the air and not holding it during the day.

PLASKON: He says the solution is to plant trees near concrete to keep it cool. But he places more of the blame on concrete's competitor, asphalt because it's black surface attracts more heat. According to the weather service, the hotter nights may be reducing humidity in Las Vegas. In Reno, the warmer nights are having a different effect - fewer days of freezing temperatures says the Climate Center's Ashay.

ASHAY: We used to average here in Reno about 180 days of freeze and in the 90's it averaged about 130 days, and a significant rise in the average minimum temperature. You can almost say that the growing season is longer now.

PLASKON: This is a local example of how human management impacts the environment. It's the topic of a Lecture at UNLV on Thursday by William Schlesinger, Professor of Biochemistry and Dean of the Nicholas School of Environment and Earth Sciences at Duke University. He says the warmer temperature fostered by human activity in Reno encourages more farming that perpetuates the problem.

SCHLESINGER: That warms the atmosphere and leads to warmer climates.

PLASKON: He says farming activates biological organisms in the ground that consume plant matter, in turn releasing carbon dioxide. The carbon dioxide or CO2 in the air traps heat and is the chief culprit of global warming. He says farming and clear-cutting have accounted for a quarter of CO2 in the air over the past century. Schlesinger was the principal investigator in the study and has testified before congress on preservation of desert habitats and global climate change.

SCHLESINGER: There is ample evidence of historical literature of societies that went out of existence because of poor management of soils.

PLASKON: His favorite example is the people of Easter Island, who clear-cut the land until topsoil eroded to the point of infertility. The islanders starved.

SCHLESINGER: I fear that we may be headed that way globally if we are not careful.

PLASKON: At the lecture Schelsinger also plans to cover the ethics of environmental stewardship citing sources, among them passages from the bible. He says despite bad management, environmental ethics aren't that foreign to humans.

SCHELSINGER: I think it is something that we have recently lost.

PLASKON: He marks 1840 as the beginning of the industrial revolution and humans lost their connection with the environment.

SCHLESINGER: And disconnected them from nature. There are so many people that think their food comes from the grocery store and it doesn't, it comes from the earth and so we have fostered, as a result of industrial society a disconnection of humans from the land that has not been healthy for conservation.

PLASKON: He says that unlike the past, when humans could move to a new place once resources are depleted, now the world is so populated there is no place to go. If humans don't learn to better manage the environment, cut back on paving surfaces, clear cutting forests and burning of fossil fuels within the next 20 years he says it will be too late.

SCHLESINGER: Looking at Las Vegas from a distance one can't help but be impressed with the degree of sprawl into nature. That means more longer commutes, people driving in single cars. One suggests that we could arrange our society differently.

PLASKON: He doesn't think Las Vegans or residents of any other city will change on their own, but he calls himself an optimist and hopes rising gas prices will force more efficient consumption and reduce environmental degradation.

Ky Plaskon, News 88-9 KNPR

TAG: Duke University Dean and Professor William Schlesinger will present "Eyes Wide Shut: The Ethics of Human Response to Global Change," at 7p.m. March 17 at UNLV's White Hall Auditorium.