Horizon, Host: Ted Simons

December 6, 2012


Host: Ted Simons

Arizona Climate


  • This past November was one of Arizona’s warmest on record. Learn about Arizona’s weather outlook with State Climatologist Nancy Selover and Randy Cerveny, a President’s Professor of Geographical Sciences. Both are with Arizona State University’s School of Geographical Sciences and Urban Planning.
Guests:
  • Nancy Selover - State Climatologist
  • Randy Cerveny - President Professor of Geographical Sciences, Arizona State University
Category: Environment   |   Keywords: arizona, climate, forecast, ,

View Transcript
Ted Simons: It appears that 2012 will go down as the warmest year in U.S. history. The National Climatic Data Center says 2012 will almost certainly surpass the record average temperature of 54.3 degrees Fahrenheit average set in 1988. It's not Arizona's warmest year, but it will definitely make the top 10. Here to talk about what's going on are two climate experts from ASU's School of Geographical Sciences and Urban Planning. Nancy Selover, Arizona's state climatologist, and Randy Cerveny, a president's professor of geographic sciences and director of ASU's meteorology program. November, December. No doubt about it, it is warm out there. Why?
Nancy Selover: For us, we're looking at the potential start of a La Nina pattern. For the previous part of the year, we had a la nina last year. Very few winter storms came down this far and that’s kind of whats happening to the rest of the country as well.
Ted Simons: How unusual is this, Randy?
Randy Cerveny: Pretty unusual. It's a little bit of a feedback mechanism, when you start to get areas with no snow, then that stays warm and it forces the cold air to stay up in Canada. The fact that we had literally no snowcover across the United States right now has helped to amplify this heating that we've had over the fall. It's something that unfortunately you don't see any easy way out, it tends to keep building and building.
Ted Simons: Are we seeing similar variations around the world, maybe unusual patterns around the world? Or is this something hitting America right about now? Any ideas on that?
Randy Cerveny: It was one of the wettest years on record in Great Britain. Their entire month of July, I don't think it went a day without raining in Great Britain. They have a storm going on over them right now. The weather patterns, as Nancy was mentioning, the weather patterns associated with the jet stream have kind of locked into place. Places get storm after storm like great Britain, and others get nothing, like us.
Ted Simons: It seemed like El Nino was shaping up in the summer and fall. Where did it go?
Nancy Selover: Disappeared, I don't know, maybe he's shy. We've had two back-to-back La Nina years, and it looked like the pattern was going back to El Nino. It got into El Nino early in the summer and then started to back off by September, back to a neutral condition. Right now somebody, a gentleman up in Colorado, thinks there's still a possibility that El Nino could develop, but he's not holding his breath and I'm not either.
Ted Simons: Are we still in a drought in Arizona?
Nancy Selover: Yes, we are.
Ted Simons: What does that mean?
Nancy Selover: If we don't start getting some precipitation soon we will be degrading most of the state. Right now most of the state is in a severe drought. A lot of the state is in moderate drought and a number of places are in severe drought. We've been in drought in Arizona for well over 14 years.
Ted Simons: My goodness. 14 years for a drought, unusual?
Nancy Selover: Not so much, for us. They tend to come in spurts. The worst one we had was back at the end of the 1800s, and that's what led to the Roosevelt Dam and Salt River Project, in terms of water supply. And then in the 1950s we had an extended almost 20 years that were relatively dry. Meaning we had more dry years than wet years. Then we had a really wet period in the 1970s and 1980s and early 1990s and now we've moved to dry. It's not a set number of years.
Ted Simons: We've got a drought here, Superstorm Sandy on the East Coast causing havoc. We've got storms pounding the west coast, raining in Great Britain all the time. Is all of this somehow connected?
Randy Cerveny: Well, yes, in that the events that cause one place's weather also impact the places around the world. But we have to keep in mind that we are also a factor that's involved with this. For example, Superstorm Sandy, that's the term everybody used, was a hurricane. It was only a Category 1 hurricane. It hit Florida, and they hardly noticed it. The big difference with Sandy is it hit the most populated area of the United States and they weren't ready for it. Is it climate change that we have a weak hurricane that hits that area? Or is it a calamity because they weren't ready for a weak hurricane to hit them? One of the things we have to be aware of, it doesn't really matter whether global warming is occurring or not. We have to think about whether we are prepared.
Ted Simons: That's a good point. Is it always going to be in the 80s in early to mid December in Arizona from now on? If so, I'm going to buy new clothes. Everybody wants to know how to prepare. Is global warming happening? Will it continue? Will the polar icecaps continue to melt?
Nancy Selover: It's not a set path of everything just gets warmer and warmer and warmer. If that's the case, this would be the warmest, replacing last year. If we are the warmest this year, it will be replacing 1998, which is more than 10 years ago. So there's a lot of variability involved in this. I don't think we will see 80-degree temperatures throughout December. We may well get into the 80s in December. There's no month in Phoenix that we haven't had 80-degree temperatures in our history. Usually it's small spurts, not giant week-long or two-week-long spurts.
Ted Simons: Randy, the idea we're trying to figure out, are these unusual weather patterns or the new norms?
Randy Cerveny: One aspect that is the new norm is the fact that we are having a very discrete impact at the local level. Our city growth has changed the climate locally. The center of Phoenix is much warmer than the outskirts. It called the urban heat island effect. We've watched that and measured it over the last 50 years. Our nighttime temperatures are increasingly hotter, even though the rest of the state doesn't experience that, simply due to the fact that the heat from all of our buildings and asphalt keeps the temperatures warmer than they would otherwise be.
Ted Simons: And with that urban heat island affect, what does that have to do with weather here? Obviously nighttime temperatures are higher?
Nancy Selover: Nighttime temperatures tend to be higher, certainly, summer and winter. But it's not -- we have -- we've had a number of people that have looked at, does the heat island steer storms around the city or block them or whatever. Theoretically, because we have all of this warmest air near the downtown area, it would be rising and tend to be sucking in, tending to create storms over the city. That's not what's going on. The storms are steered down off Mogollon Rim. When they get to the dry space which is Phoenix, all day long, whatever moisture we've had has evaporated, it's carried away and gone. We have drier air over the city, so the storms get here and run out of energy. Sometimes they will hit the East Valley before they run out of energy, and sometimes they actually come through and Phoenix gets a storm and we all cheer.
Ted Simons: Are there ways to address the heat island effect that we're not looking at? The rooftops, reflecting off the rooftops, what's going on with the plans?
Nancy Selover: There are a lot of strategies being looked at. ASU has a number of people looking at strategies with permeable pavements so you can do urban forestry. You can put more trees in because the tree root doesn't die because it's in this little three foot by three foot box. Air is not heated by the sun. It's heated because the surface is hot and the air is heated by proximity to the surface and it's carried up. Cool air strategies, green roof strategies, not just the color that reflects the sun but there are properties in the paints and materials that don't absorb as much radiation as some of the materials we've used in the past.
Ted Simons: What are we going to do about these haboobs in the summertime? It looks like a Ken Burns documentary out here. Are we going see more of these things?
Randy Cerveny: That's a nice analogy. The storms created during the Dust Bowl basically are the same storms we see over the summer. The great haboob of last year was a result in part of all that dust that had been accumulating because of the dry conditions that we've had. You get a storm that doesn't have rain, all it really has is wind and we get these big dust bowls. They had no storms in the dust bowl days, they had no rain.
Ted Simons: A relative thinks of moving to Arizona, what's the weather like out there. What do you say? In the next five to 10 years, what will Arizona's weather and climate be like?
Randy Cerveny: There are some things we can say and some we can't. Our nighttime temperatures in the urban area will continue to gradually get a little bit warmer as the city continues to grow. I think that we can say that if this idea of cyclical drought, as in the 1930s and 1970s and 1990s and so on, that should be coming to an end. We've had 15 to 17 years of drought. By the 2020s, we should get back to a wet period if everything else is consistent. We might have to worry more about more flood situations in Arizona than actually these dry haboobs.
Ted Simons: That'll take a lot of imagination. Good to have you both here.

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