Humans are destroying our planet.
Why are temperatures rising so fast at the Seattle-Tacoma International Airport? It's complicated. MANOP1984 / GETTY IMAGES

We just finished the hottest decade ever recorded at Sea-Tac Airport—by a longshot. The average temperature at the Seattle area’s most watched weather station was 53.8 degrees Fahrenheit this decade, 1.5 degrees hotter than last decade’s average, and a startling 3.6 degrees hotter than the average temperature in the 1950s, when the airport's earliest weather data was collected.

In addition, the first, second, and third hottest years ever recorded at the airport (2015, 2014, and 2016, respectively) all occurred within the last ten years, according to Joe Zagrodnik, a Washington State University meteorologist who crunched the numbers for me.

What's going on?

At first glance, Sea-Tac’s weather data seems to be announcing the beginning of a climate apocalypse. But before you trade in your gas guzzler for a bus pass (actually, do that anyway), I should mention that Sea-Tac is not a perfect station to measure our entire region’s weather. No single weather station can measure regional changes and Sea-Tac’s weather has likely been affected by 60 years of nearby urban growth and airport expansion. In addition, when you sample more data points our region actually appears to be warming to a much lesser degree than the Sea-Tac data reflects. By some measures, Washington is actually the slowest warming state in the country.

“This record at Sea-Tac wouldn’t be enough on its own to draw conclusions from,” Amy Snover, director of the UW Climate Impacts Group, said an e-mail. “But the trend is consistent with longer-term trend across the state… region… nation…. and globe... over the last 115 years. Most of the global temperature increases since the 1950s were caused by human activities (emissions of greenhouse gases, primarily by burning fossil fuels).”

In other words, Sea-Tac’s weather is both a harbinger for the sweltering world ahead of us and somewhat of a red herring in understanding the precise nature of our regional weather.

That makes it worth paying attention to.

The Airport Is Getting Hot

There appears to be a clear signal in the average temperature at Sea-Tac across the last 60 years: the airport is heating up significantly.

Five out of the last six decades were warmer than the previous ten years, with the 1950s and 2010s seeing the largest jumps.


During that same 60-year period, global emissions of carbon dioxide and other greenhouse gasses—gases that warm our planet by trapping more heat in our atmosphere—have skyrocketed. Carbon emissions in the 1950s were around 5 billion tons of carbon dioxide per year. Now they are over 35 billion tons per year and rising. There were 316 parts per millon (PPM) of carbon dioxide in our atmosphere when scientists first started measuring it in 1958. It’s now over 400 ppm.

But something else happened at Sea-Tac during that same period of massive carbon emissions: a new region was growing. Millions of people moved into the Seattle metropolitan area during that time and the airport itself expanded and added new runways made of heat-emitting concrete.

Those changes likely affected the weather at the airport, according to Karin Bumbaco, a staff member at UW’s Joint Institute for the Study of the Atmosphere and Ocean and the state’s assistant climatologist.

“Increases in development can definitely impact temperatures in urban areas, and there is some evidence that the addition of a third runway at Sea-Tac in the early 2000s has warmed temperatures, especially in summer,” Bumbaco said in an e-mail.

Mark Albright, a UW weather researcher, said that a combination of urban development, the development of Sea-Tac’s third runway between 2005 and 2008, and other less understood weather patterns make Sea-Tac’s weather less representative of the region.

“It's complicated, but much of the warming experienced at Sea-Tac since 1945 is likely due to urban development in and around the airport,” Albright said.

Albright said he instead uses the Olympia airport, which has had less urban development, to measure Puget Sound’s weather. He said that weather station actually shows a drop in average temperatures, with 2019 showing a 0.8 degree Fahrenheit drop from the average temperature in the 1990s.

This isn’t the first time Albright has questioned the accuracy of a climate change statistic.

In 2007, former Seattle Mayor Greg Nickels wrote an editorial in the Seattle Times claiming the snowpack in the Cascade Mountains had been reduced by 50 percent in the last 50 years. Albright didn’t think that was right, so he e-mailed the Times and a collection of other climate scientists. All of the experts agreed that the 50 percent number was wrong but a fight ensued over what the correct figure was. Albright and his boss at the UW, Cliff Mass, said the snowpack had shrunk by 10-15 percent. Philip Mote, a UW scientist and the Washington State Climatologist at the time, said it was 35 percent.

Albright, who was the state’s assistant climatologist at the time, wouldn’t back down and kept e-mailing. Eventually he was forced out of his volunteer position as the state’s assistant climatologist over the battle.

Albright and Mass are part of a local group of climate scientists who are warning of both the dangers of climate change and also the dangers of inaccurate fearmongering by climate change activists. In a recent blog post, Mass claimed that media companies like the New York Times and climate activists like Greta Thunberg are engaging in “unconscionable exaggeration, hype, and fear-mongering” that is “ungrounded in science.”

The truth is that some very irresponsible folks are hyping and exaggerating the impacts of the minor global warming we have had so far, sending vulnerable individuals into a panic. And these irresponsible folks and individuals are painting an apocalyptic view of the future that is completely at odds with the best science.

Mass, who in 2017 debated this very issue at length with The Stranger's Charles Mudede, told me the best measure of our regional temperature growth is to use a collection of regional weather stations that have been checked by the National Weather Service.

Mass said that when you look at regional weather data, our warming is actually far less than what Sea-Tac data suggests.

“[There’s] still a warming but less (by roughly 1.5 F)—this makes more sense,” Mass said in an e-mail. “The question is how much is natural and how much is human caused global warming. I suspect partly both, with the anthropogenic [human-caused] signal probably being larger.”

So, even the most skeptical local scientists say our region is warming, but there’s one more caveat to throw in the mix here: all of these figures are measurements of past weather, which is categorically different than our climate. Weather and climate are frequently confused by people across the political spectrum, from Donald Trump claiming cold winters are proof of climate change is a hoax (they are not) to climate change activists claiming summers full of forest fires are proof that the climate is warming (they are also not).

Weather is the collection of events that you feel when you leave your house, while climate is the abstract prediction of weather events. Or as the National Oceanic and Atmospheric Administration describes it, “Climate is what you expect, weather is what you get.”

Scientists use “what we get” or, more accurately, “what we got” to help understand our climate and make a better determination of what to expect. And even with the irregularities around Sea-Tac’s weather station, it’s still worth paying attention to when trying to understand what we will get in the future, especially for poorer people who disproportionately live closer to sites like aiports, according to WSU’s Zagrodnik.

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“The temperature at Sea-Tac doesn't tell us much about global climate,” Zagrodnik said. “But it does tell us what we directly experience here in Seattle and is important for thinking about how to make our city resilient to climate change, for instance by reducing the urban heat island effect. And there is a social justice element to that as well, because the hotter areas with less tree cover in Seattle are disproportionately populated by underrepresented groups.”

The Lows Are Getting High

There are reasons to believe that the warming at Sea-Tac is consistent with what is happening throughout our urban areas. The Office of the Washington State Climatologist uses multiple weather stations to create a “Seattle Urban Site” measure of the city’s weather and still finds significant warming over the last 60 years.

“[T]hat site shows +1.3°F of warming since 1950, a smaller amount of warming than the Sea-Tac station alone but still a statistically significant warming trend,” Bumbaco said.

The data for Seattle’s urban site shows an even larger increase when you look at the average nighttime low temperatures, a measure that some scientists say is better for understanding climate change. The daily average temperature increased 1.3 degrees Farenheit, but the average nighttime minimum temperature increased by 1.9 degrees Fahrenheit since 1950, a substantially larger increase.

Snover said this increase in nighttime lows is consistent with the scientific understanding of greenhouse gases like carbon dioxide.

“Because of the way greenhouse gases trap heat in the atmosphere, we would expect minimum temperatures to have larger trends than daily maximum temperatures—and this is what we have actually observed occurring,” Snover said.


Nick Bond, the Washington State Climatologist, said having more carbon dioxide in the atmosphere is causing Seattle’s nighttime temperatures to feel more like the American South, where humidity causes warm summer nights.

“People that have lived in the Puget Sound region for an extended period have perceived that it is getting a bit more humid (it is more obvious in summer) and that trend is entirely consistent with the upward creep in nighttime temperatures,” Bond said.

Measuring weather and predicting climate change is complicated but amidst the noise of the data and the climate change debate one thing is clear: Seattle and its airport are getting warmer.