PHOENIX — You might have noticed the brown haze hanging around the Valley lately. New data shows some pollutants in the air have increased significantly.

According to data from Boston University analyzed by The New York Times, carbon dioxide emissions in the Valley increased 291% from 1990 to 2017.

"The results are not that surprising," said Mikhail Chester, an associate professor of civil, environmental and sustainable engineering at Arizona State University. "You're largely seeing the growth of the population over the past 20 to 30 years."

While CO2 emissions have gone up a lot, emissions monitored by the Arizona Department of Environmental Quality have gone down by about 60% from 1990 to 2015. The drop is attributed to better fuel economy. 

"Which means more dollars in your pocket, but it also translates to fewer pollutants coming out of the tailpipe of your vehicle," Chester said. 

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Chester added that there are, however, more people are on the roads. And those cars are producing CO2, which is what's coming out of your tailpipe instead of what Chester calls pollutants of immediate public health concern. 

"We're essentially making the choice that we would rather have eliminated the direct public health concern for the indirect," Chester said. "And the indirect I'm referring to are the public health issues that come up with climate change."

Chester said the effects of climate change are felt in the metro area now and added it could get worse.

"Obviously, heat is at the top of our list, right?" Chester said. "The global climate models show that within 30 to 40 years, we could be experiencing hotter extreme heat waves in Phoenix or prolonged heat waves in Phoenix."

Chester said the implications will be more widespread, like infrastructure breaking more, and more people dying or hospitalized because of heat.

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Poor Air Quality in Phoenix
Poor air quality in Phoenix on Jan. 1, 2018.
Bianca Buono/12 News