image title

Reimagining cities' (and our) role in climate change fight

April 29, 2022

Urban climate expert Karen Seto offers insights on how cities can help solve climate crisis in ASU talk

The science is out and unequivocally clear: Climate change is a threat to human well-being and the health of the planet. In the last decade, urban infrastructure and activities caused about two-thirds of today's greenhouse gas emissions — and while cities continue to be a big driver of emissions, one urban climate expert says that they too need to be critical pieces of our climate solutions. 

Karen Seto, co-lead author of the urban mitigation chapter of the United Nations Intergovernmental Panel Climate Change (IPCC) Sixth Assessment Report and a professor at Yale University, spoke to nearly 100 Arizona State University researchers, community members and students last week at the Anthony J. Brazel Lecture hosted by ASU's Urban Climate Research Center

The title of her talk was “Cities and Climate Change: Key Findings From the IPCC 6th Assessment Report.”

“Speakers such as Dr. Seto bring important perspectives to our ongoing work on climate, enhancing our discourse and growing our global research network,” said David Sailor, director of ASU's Urban Climate Research Center and professor in the School of Geographical Sciences and Urban Planning. “I’m particularly proud of the opportunity that the Brazel lecture gives our students and young researchers to interact with luminaries in the field.” 

According to the UN’s latest series of climate change reports, the past decade saw the highest level of average yearly greenhouse gas emissions from human activities ever recorded, and a startling companion message from the report: “We’re simply not on track to limit warming to 1.5 degrees Celsius” — the internationally recognized threshold that if breached would result in extreme natural catastrophes like severe droughts, food shortages and extreme heat waves all around the globe.

“Any further delay in concerted global action will miss the brief, rapidly closing window to secure a liveable future,” said Seto to a full crowd in ASU’s Memorial Union Alumni Room. “We have this window, and it’s rapidly closing.”

As the world’s population is expected to rise by 2 billion people within the next 30 years, with nearly 70% of the world’s population estimated to live in cities, the call for action becomes even more urgent and personal. 

While a handful of cities across the world have already begun adapting to reduce their emissions, and adaptation is increasing all across the globe, progress is still uneven and not happening fast enough, Seto says, especially in the places that are most at-risk to a warming climate’s effects. 

“We need to simply accelerate adaptation,” Seto said. “No cities are safe from climate change impacts until all cities are safe from climate change impacts.”

Solutions across all sectors

The latest U.N. report outlines mitigation strategies and solutions across different critical sectors and discusses the practical steps that cities — which are at the confluence of all these sectors — can take to help curb greenhouse gas emissions. 

Strategies across different sectors include: 

  • Major transitions in energy to low- or no-carbon energy systems and the electrification of our energy systems (energy sector).

  • Transitioning to low-carbon transportation like electric vehicles or changing demand to use less vehicles in more walkable cities; and transitioning to alternative fuels (transport sector).

  • Retrofitting existing buildings rather than building new buildings (building sector).

  • Leveraging new technology that enables us to be more efficient to reuse, recycle and minimize waste (industry sector).

  • Prioritizing carbon capture as a key part of the solution space to get to net zero emissions (land use sector).

Karen Seto spoke to a room of nearly 100 ASU researchers, community members and students at the Anthony J. Brazel Lecture last week, hosted by ASU’s Urban Climate Research Center. Photo courtesy of David Sailor

Additionally, Seto emphasized a new sector included for the first time in the U.N.’s report on climate change, focused on practical solutions around changing “demand and services.” 

“It's really clear that we can have a very high standard of living and still reduce our demand for energy,” Seto said. 

The U.N.’s report shows that if we change demand, it has the potential to bring down global emissions by 40–70% by 2050. 

“It’s about changing how frequently we use our cars; it's how frequently we get the new iPhone; it's (about) changing our consumption habits: walking, cycling, public transport; it’s transitioning to a more sustainable diet,” Seto said. “It really focuses on what we can do as individuals to change our consumption habits.”

But Seto made it clear that if we do not first have infrastructure that is designed for us to walk or take public transit, these are not options at the local level. Urban planning must play an important role for cities to create the opportunities for people to change behavior. 

Not one-size-fits-all 

Seto says that the literature is clear that urban mitigation strategies will be different for different types of cities based on a city’s unique physical characteristics and how fast it is expected to grow. 

“Are you in a city that's rapidly growing, or are you in an established city, and what kind of footprint do you have?” said Seto. “That will actually determine the entry point for whether you should focus on spatial planning or whether you should focus on electrification or really focus on changing demand.” 

For a city like Tempe, she imagines a focus on spatial planning, and then also identifying entry points for changing demand and behavior.

Prioritizing climate change 

Moving into the future, Seto says that although technology exists to advance many of these urban solutions, two large obstacles to implementing these solutions still exist: green finance and political will. 

“I don’t know of any city that thinks that climate change is the No. 1 thing that they should (deal with),” Seto said. “We need to think about the policy hooks or strategy hooks that will engage city leaders, and that will vary depending on the city.” 

Seto explains it could start with reframing how we communicate climate change adaptation as a co-benefit, with other issues taking the lead role.

“Right now, we're thinking you need to do climate change and the co-benefit is health, and co-benefit is improved jobs. Well, no, that's not how cities think about it. Cities think, ‘How do I bring in more jobs?’” Seto said. “I'm absolutely convinced having read so many papers for the assessment that we have the solutions, but it's a matter of packaging them together and thinking about what is feasible.”

As part of that, Seto believes that with both the science and solutions in hand, what is missing now is a parallel process that takes the cutting-edge science and implements it.

“When we think about the implementation, the implementation is going to vary by country, by capacity, by geography, by priorities. And so, I'm not really sure how to organize it,” Seto said. “How can we not just hand over this report, but be part of the solution to implement the report?

“Part of why I'm here is to hear from all of you what you think. I think all of us have a role to play in being part of the solution.”

The Urban Climate Research Center (UCRC) at ASU is a globally recognized and respected group of scholars studying a wide range of urban climate topics. Composed of nearly 40 faculty affiliates across eight schools at ASU, UCRC employs a collaborative social/physical science framework to address critical issues in the urban atmospheric environment. Learn more at

Top photo: Karen Seto delivers the the Anthony J. Brazel Lecture. Photo courtesy of David Sailor

David Rozul

Media Relations Officer , Media Relations and Strategic Communications


image title

Shedding light on Phoenix's most heat-vulnerable

March 18, 2022

ASU student aims to better understand what communities are under more risk of heat-health threats

There’s no debate, heat-related illnesses are common during the summer in Phoenix.

Year after year, nearly 3,000 people visit Arizona emergency rooms because of heat-related illnesses. Heat-related deaths have increased by more than 180% in the last decade, and in 2020, there were 323 heat-related deaths in Maricopa County alone. 

Cities like Phoenix are relying on current heat-vulnerability models for mitigation strategy decision-making that, while helpful, are fraught with limitations — due in part to the way they are constructed and the data used — and risk, leaving out some of the most vulnerable populations in need.

Joseph Karanja, a graduate student in the School of Geographical Sciences and Urban Planning, is conducting research to create one of the most holistic views of how heat disproportionately impacts specific communities around Phoenix to better understand how we as a city can help arm the most vulnerable against looming heat-health threats.  

“Comparing outcomes in Maricopa County, homeless account for about 40% of the deaths, yet census datasets (the information that powers current heat-health modeling) cannot account for that population,” Karanja said. “We are simply relying on these data because of the absence of an alternative. I want to challenge that. I want to prompt people to think of alternative data sets and alternative ways of thinking.” 

In his research, Karanja interrogates not only what variables are most important to include in heat-vulnerability models, but using statistical techniques, he creates new ways to unify disparate information to gain new perspectives on how communities are experiencing varying heat stress and heat-health impacts. 

Karanja recently presented a commentary paper titled “Methodological Rationale for Heat Vulnerability Indices as Predictors of Heat-Health Outcomes” at the American Association of Geographers annual meeting in February, discussing a portion of this research.

“There has been an increasing amount of work, globally, focused on improved understanding of what variables serve as the best metrics for assessment of heat-health outcomes,” said Matei Georgescu, associate professor in the School of Geographical Sciences and Urban Planning and a co-author of the study. “Where is exposure to extreme heat greatest? Which populations have the greatest sensitivity to extreme heat? What barriers, both physical and social, need to be removed to enhance the capacity of populations to adapt to extreme heat?

“Joseph's work directly tackles this critical research gap by focusing on simplifying the overall approach through a re-conceptualization of the very methodological aspects that are the foundation for heat vulnerability indicator development. His work is helping to reshape the very foundation that is required for characterizing heat-health outcomes across global cities.” 

portrait of Joseph Karanja in front of a map

Joseph Karanja.

Reenvisioning a complex process and unifying data 

At the heart of his research, Karanja is creating a new composite heat-vulnerability metric — a metric that combines not only biophysical (heat) data, but also socioeconomic data from various sources to give researchers and policymakers a finer lens into who is most heat-health vulnerable.

Karanja explains that by coupling these metrics and finding the optimal way to meld them together, his research hopes to capture the overlooked nuances of how heat disproportionately affects communities, which include: differences in how heat exposure impacts people living in different geographical parts of the city that may or may not have infrastructure that can reduce heat impact; and differences in income and people’s ability to have reliable access to air conditioning or beneficial tree canopy in their yards. 

“We need to continuously look at the current data, new data; evaluate how we are continuously constructing metrics; see how those metrics influence health outcomes and inform decision-making; and at the same time, (think about) how do those health outcomes inform the construction of the metrics and the collection of data in the first place,” he said. “We're creating a feedback loop system.” 

Karanja’s research not only interrogates the metrics we currently use, but evaluates our current approach to the process, reimagining it as an evolving cycle that will continue to be refined as more information becomes available. 

“I have never met a student with a greater desire, an unquenchable thirst, to learn,” said Georgescu, who serves as Karanja’s academic adviser. “He is undaunted by challenges and is unfazed at immersing himself in completely new fields. Joseph is a future global star. I am very excited to be a part of the next three to four years of his experience at Arizona State University.

“I am equally excited to see where his passions and thirst for making a global difference lead him down the road, beyond ASU.” 

A world away 

Karanja’s research and educational drive have ties to a humble beginning. 

A native of Webyue, Kenya, a modest town near the eastern border of Uganda with makeshift settlements and a sugar cane plantation, Karanja says it’s his community that rallied around him and enabled him to pursue his educational endeavors.

“I was brought up by a single mother, so my story is being part of a lot of struggle in Kenya,” Karanja said. “Basic education was not free at the primary school level and in secondary school level. It's actually the community that came together and sponsored me to get to high school.”

He went on to receive a bachelor’s degree in Kenya from Kenyatta University with a focus on environmental planning and management, focusing on rural neighborhood planning, regional and urban planning, and governance issues that relate to planning and design. He says he sees his work today with analyzing heat vulnerability as a mechanism for better understanding society. 

“When I came to the U.S., I really wanted to study urban planning, but I realized having been brought up in squalor-like settlements, there are so many urban challenges,” Karanja said. “If you are to solve challenges tied to heat, to some large extent, you are dealing with climate change problems associated with population growth and rapid urbanization.

“You’re, in a way, solving so many problems just by looking at heat in all its multi-dimensionality.” 

The right place to start 

Karanja hopes his research not only will lay the groundwork for future heat-vulnerability models to better characterize heat-health outcomes in cities, but one day, he hopes to be able to conduct similar research in his home country in Kenya. 

He credits his supportive environment throughout his academic career for the opportunities he’s had and the impact he plans to make. 

“I want to thank people who have been significant in my life, believed in and nurtured me,” Karanja said. “I’ve had a very supportive environment, and to provide some contribution to the scientific community towards the construction of heat matrices, I believe here at Arizona State University is the right place to start.”  

Top photo courtesy

David Rozul

Media Relations Officer , Media Relations and Strategic Communications