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Southwest’s drought & fires are a window to our climate-change future

This story was originally published by ProPublica.

ProPublica is a Pulitzer Prize-winning investigative newsroom. Sign up for The Big Story newsletter to receive stories like this one in your inbox.

The concentration of carbon dioxide in Earth’s atmosphere has reached its highest level in recorded human history. Again.

In April, the level of CO2 was 27% higher than it was 50 years ago, according to the latest data from the National Oceanic and Atmospheric Administration and the Scripps Institution of Oceanography. (Methane, a gas with about 85 times the near-term warming effect of CO2, has risen more than 16% since 1984, the first full year that NOAA collected data.)

Each spring, going back decades, we have surpassed the previous year’s CO2 record, as humans continue burning hydrocarbons at breathtaking rates, releasing greenhouse gasses. That impacts temperatures, precipitation, the intensity of storms and other weather patterns.

Across the American Southwest, this has amplified record droughts and fires.

Climate change is exposing where the bodies are buried, literally. Boaters and paddle boarders discovered two corpses in early May in Lake Mead, as water levels fell to their lowest point since the reservoir was filled in the 1930s. Lake Powell has also dropped to its lowest point since being filled.

The ongoing drought appears to be the worst in 1,200 years, according to research recently published in the journal Nature Climate Change. Around the region, there have been hotter temperatures, smaller snowpack and an earlier start to the fire season. Wildfires have already torched more than 300,000 acres near Santa Fe in northern New Mexico this year.

This new reality threatens the Southwest, the fastest-growing region in the U.S., and the 40 million people who rely on the Colorado River, while offering a glimpse at what climate change will bring there and elsewhere.

“This happens to be one of those years when we can look out the window and look at the future as the smoke pall floats overhead,” said David Gutzler, a professor emeritus who researches climatology and meteorology at the University of New Mexico’s Earth and Planetary Sciences department.

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To better understand how climate change is and will continue to affect the Southwest, ProPublica spoke to three experts: Gutzler; Mikhail Chester, a professor in Arizona State University’s engineering school and the director of the Metis Center for Infrastructure and Sustainable Engineering; and Gregg Garfin, a climatologist at the University of Arizona and co-lead author of the Southwest chapter in the Fourth National Climate Assessment.

The conversations have been edited for length and clarity.

Wildfires are burning near Santa Fe, while the Boulder, Colorado, area is still reeling from a fire that burned a developed area in the dead of winter. What are the connections between a changing climate and wildfires?

Gutzler: We make the extremes worse. That’s a bit different than saying a wildfire is caused by climate change. As temperatures rise, hot temperature-related extreme events are likely to become more frequent and more severe, and that’s exactly what we’re seeing across the West right now.

Garfin: There are also parts of the region where there’s a link between fire severity and climate change. The way that plays out is that climate change affects the hydrology, so it leads to a shorter snow-cover season, less snow-covered area, soils that are desiccated, and then temperature also puts stress on trees that dries out the fuels.

Research also suggests the Colorado River’s flow is down about 20% this century. How might the region’s river systems be shaped by climate change?

Gutzler: We should plan for diminished flows, particularly out of snow-fed rivers. ... What snow there is melts earlier and melts faster. That’s exactly what we saw this year. In the Rio Grande Basin, snowpack was pretty close to what most people would consider average right around the time of peak snow, a month and a half ago. But it has just melted really fast in this hot weather, so the effect of that on streamflow is we get less flow in the river for the same amount of snow that fell last winter.

Garfin: We’re seeing less snow-covered area, less water content in the snowpack, early runoff in the late winter and early spring at elevations lower than around 7,000 feet, an increased fraction in the precipitation that we get coming as rain rather than snow and reduced soil moisture. All of these things combine to reduce the efficiency of runoff. ...

We’re already seeing an increasing water supply coming from treated effluent that’s primarily being used to irrigate parks or golf courses. Probably we’ll be seeing more of our potable water supply coming from treated effluent. Another thing — we saw this in Arizona in the State of the State address from Gov. (Doug) Ducey — he said let’s put billions of dollars into developing desalinated water supplies, and there have been plenty of feasibility studies. It’s expensive and it takes a lot of energy, but we could end up with some technological breakthroughs. ... Water managers throughout the Colorado River Basin have been creative in finding ways to keep more water in the reservoirs. Obviously that’s not enough, but I think there will be water marketing and trading maneuvers — because some tribes have large amounts of water — to create the legal mechanisms for the cities to buy more water from tribes.

What about the impact of climate change on living things in the region? What do we know about changes to ecosystems and biodiversity?

Gutzler: The change in the climate is happening at the same time as humans affect ecosystems in other ways that aren’t connected to climate change, just by habitat destruction and all the other things that people do to change the environment. I view climate change as an added stress to wild ecosystems that are already stressed by large numbers of people moving into the Southwest.

One way for mobile species to adapt to climate change is to move north. ... If people have built fences or, at the U.S.-Mexico border, a wall, then the combined effect of a changing climate and barriers to migration can jeopardize the health of species and ecosystems.

In addition to biodiversity, how does a changing climate interact with the Southwest’s rapid population growth?

Garfin: We’ve got a lot of people who have built their homes or expanded towns into the so-called wildland-urban interface, and that puts infrastructure at risk (to wildfires). Also, if we have severe fire, eventually there’s going to be rain — it doesn’t even have to be record rainfall — and all that stuff that has burned is going to find its way into watercourses. We end up with debris flows that can take out infrastructure, that can take out roads or that can end up in reservoirs and increasing the sediment load and decreasing water quality.

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Chester: We are figuring out already how to deal with extremes in terms of heat, in terms of monsoons, in terms of drought that are beyond the forecasts of most other places in the United States. The worst of the worst in a particular place in Illinois, let’s say, is probably not close to what you get in Phoenix, so we’re already living with these extremes. ... For the most part, things aren’t breaking right now. ...

Now, you’re running into the reality that the conditions that we’re designing for are not necessarily what we will live with in the future. So, if we designed for 120 degrees Fahrenheit maximum temperatures, is that what’s going to be the max 20 years from now, 30 years from now, or is it going to be greater?

If the Phoenix metro area is doing pretty well overall, are there any examples of infrastructure that’s already nearing the breaking point?

Chester: You get a lot more blackouts and brownouts in the power system when you have these heat waves. That’s the case anywhere in the U.S., but you certainly have that here. You get inundation of the stormwater system. ... Everything breaks more frequently when you have hotter temperatures. That’s the simpler way of looking at it.

The Southwest is a very ethnically diverse region. How does that affect the calculus as society pursues solutions?

Garfin: If we don’t deal with equity in climate solutions, then we’re going to shoot ourselves in the foot. Through the impacts to vulnerable communities and less economically well-off communities, it’ll end up being more costly anyway. ... Previous failures were that housing developments in less affluent parts of our cities have typically lacked the kinds of landscaping that would reduce the heat-island effect and that would absorb more stormwater, so we know that now and we know that we haven’t done well by those communities.

The Intergovernmental Panel on Climate Change published reports this year that came with a warning — we’re likely to miss the Paris Agreement’s goal of limiting warming to 2.7 degrees Fahrenheit. What does that mean for the Southwest?

Gutzler: We’re living it this year. ... You can take an extreme drought of the sort that we’re experiencing now and the way that it has impacted the environment, the water supply across the board, and say that is the direction the Southwest is headed unless we do something about climate change.

Garfin: We already have amplified heat in our cities from the urban heat-island effect, from just changing from natural vegetation to the built environment. Also, as you increase the background temperature, the effects that we see in our large cities — Phoenix, Tucson, Las Vegas — more people are exposed to the public health effects of extreme heat. ... In places like Tucson or Las Cruces, our future might look like Phoenix, and Phoenix’s future might look like Middle Eastern cities. ... Then, what’s projected is continued decreases in snowpack, perhaps more extreme high flows, but more days with very low flows. That leads to a much less reliable surface water supply.

Are there examples of steps being taken in the region to address climate change through mitigation or adaptation?

Garfin: If we look to some of the more progressive climate change plans like Flagstaff’s Climate Action and Adaptation Plan, they’re doing a couple things in terms of wildfire. One is insisting through their public policy that there’s more defensible space around houses and other structures that are in the wildland-urban interface. Then, they also had a bond in 2012 where city residents overwhelmingly voted to tax themselves to pay for forest treatments on public, federal lands in their watershed to reduce the risk of really severe fires.

Chester: There’s got to be a readjustment of how we utilize ecological infrastructure. ... You’re going to have a lot of small-scale failures, and at times it might make sense to allow those failures to happen.

I’m not suggesting we allow loss of life. I’m not suggesting we allow major economic damages. So, a great example here of safe-to-fail infrastructure is Indian Bend Wash in Scottsdale. We’ve basically said, when the monsoon rains come, we are going to allow a giant river to move through the wash, and it might take out the golf courses, the bike paths, the Frisbee golf, the dog park. ... The cost of replacing it is pretty low, but the benefit we get is enormous. The benefit is social in terms of all this space. The benefit is ecological; there’s a lot of green infrastructure in there. There’s also the benefit of stormwater attenuation.

With all this in mind, what does the future hold for the Southwest?

Chester: The problem — from my perspective as an engineer who studies infrastructure — is the rigidity of everything we’ve built out. ... For the past century we’ve gotten away with these design assumptions that things can be rigid, can be based on a future that is largely predictable. Here we are in the future saying that doesn’t seem to be the case. We need a lot of flexibility.

Gutzler: Ultimately, carbon energy will be replaced on purely economic grounds by renewables, so there’s hope there. But the Southwest is inevitably going to become a hotter and drier place than it is now with huge stresses on human societies and wild ecosystems. That’s what’s in store for us, so we better adapt to it as intelligently as we can.

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Gene Moreland/TucsonSentinel.com

Lake Mead National Recreation Area in Nevada. Two corpses were discovered in early May in Lake Mead, as water levels fell to their lowest point since the reservoir was filled in the 1930s.