The following is a transcription of the August 2023 climate conversation between Denver7 chief meteorologist Mike Nelson and Colorado Public Radio’s Ryan Warner for CPR’s “Colorado Matters” show.
Listen to “Colorado Matters” Monday-Friday: 9 a.m.-10 a.m. & 7 p.m.-8 p.m.; Sundays: 10 a.m.-11 a.m.
In this week’s discussion:
- Colorado's rather busy severe weather season this year
- Record-breaking heat in Colorado - past and present
- Our changing climate and what it means for the future
- What's in store for the fall given our wet spring and summer and the development of El Niño
RYAN WARNER: This is Colorado Matters from CPR news and KRCC, I'm Ryan Warner. It's been an extraordinary year for severe weather in Colorado. Our climate team crunched the numbers: For hail, thunderstorms and tornadoes this year – 1,400 storm reports. Last year? Five-hundred or so - it's the busiest in a decade. That's where we'll start our regular conversation with Mike Nelson, chief meteorologist at Denver7; he joins us regularly to discuss climate and weather. Hi, Mike.
MIKE NELSON: It’s nice to be again with you, Ryan.
RW: To cast these numbers a little differently, we had nearly as many storm reports in June as all of 2022. What is going on?
MN: This year, we had a cooler than average summer. We've had about 25 days, I think, of 90 (degrees) or better – we have not hit 100 (degrees) – and that's because we've had a northwesterly jet stream flow for the bulk of the summer, which brings cold fronts through the area and with those cold fronts, we get severe thunderstorms. So, starting in early May, I think it was on the 3rd when we had 26 tornado warnings in one day, which was more than I issued for all of last summer on through June and July. And right now, we're in the midst of heavy rain potential this afternoon across much of the state because of the remnants of a tropical storm.
RW: Why don't we talk about this cooling period? – Well, maybe, first, we could talk about the heat. Yeah, let's talk about the heat. We are getting a bit of a reprieve from it.
MN: We have had it locally, Ryan, and that does not mean the globe is not getting warmer from climate change, because many areas just to the east of us have had a searingly hot summer from the Midwest all the way down across the Gulf Coast – heat advisories and warnings just about every single day. So, we've been very lucky we've had the rain, we've had the cooler weather. Unfortunately, that rain and cooler weather has also been accompanied by tornado warnings and hail.
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RW: Stepping outside earlier this week felt like getting a bear hug from a toaster. Inside, it's been miserable without air conditioning. Here's a fourth-grade teacher in Jefferson County (who wants to remain anonymous). She told me on Wednesday, the AC in her classroom was broken:
[Well, it hasn't been below 80 (degrees) always. It's gotten up to 89 (degrees) in my classroom. My teammate has been up to 91 (degrees) and the teacher down the hall has been up to 94 (degrees) in their classrooms. We have had issues where if the air is blowing, it's blowing hot air into our classroom. The kids are miserable. We've had a couple of bloody noses, a lot of headaches, stomach aches, and just struggling to stay with me in a lesson because they are so stinking hot.]
RW: Did we see records broken this year, for heat?
MN: As far as temperatures, not really. But anytime that the readings get up into the 90s and you don't have AC, it's going get really warm inside of a building and those poor teachers… I mean, that's hard enough work anyway, and to try and teach those little learners when they're overheated, that's very rough.
RW: You and I have talked about this in the past but you know, there was obviously a good stretch in Colorado – as homes were being built – where air conditioning wasn't de rigueur, that living in Colorado meant it was okay to do so without air conditioning.
MN: When we first moved out here in 1991, the realtor asked us in a home we were building, ‘Do you want to put in AC? Because historically, a lot of people choose not to.’ And we put it in at the time because our son, who was 5, had asthma and allergies, and we thought it would be better to put it in. But even then, just that amount of time, people still didn't necessarily do it. I think now, they don't even ever ask that question.
RW: Hhm. Do I have it right, the Denver might have set a record of 99 this week, though?
MN: We did have some record highs. We did have (a high of) 99 (degrees) earlier this week. And that's been the second time this summer we've hit 99 for a daily record. But the more important record that we had earlier this week was a morning low of 73 (degrees). Which typically at night, it cools off into the 50s or low 60s here. Seventy-three (degrees) was the warmest morning low temperature that we've ever had in the month of August, and second only to 77 degrees on the 3rd of July back in 1881, which still stands as the warmest overnight low temperature, so that was noteworthy.
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RW: I'd like to look outside Colorado for a moment at… well, jaw-dropping climate catastrophes. The fires in Maui. A hurricane that reached my desert hometown, Palm Springs, California. Mike, my mother remains in disbelief:
[The homes that have been destroyed here with mud flows that are four feet tall from nowhere that's not vacant lots or hillside homes. It's just astounding, astounding.]
RW: A new term that's being used to describe this is, compound disasters. Extreme weather amplifying other effects, and that could include human errors with things like disaster response. When it comes to climate change, have we moved past the mitigation stage to the adaptation stage?
MW: Absolutely. And the cause is, of course, the increase in greenhouse gases, namely carbon dioxide, but also methane from the burning of fossil fuels. And in my lifetime, when I was born in 1957, we were at 310 parts per million (ppm) of CO2 in the atmosphere. We are now at 420 (ppm). So we have added 50% more carbon to the atmosphere in the past 65 years. And unfortunately, that rate of increase is not declining as it should, we still are adding way too much – about 100 million tons of CO2 into the atmosphere every single day – and the lifespan of that is centuries. So, we have baked in this problem and we are definitely at the adaptation stage now. And that's going to mean, how do we deal with it? Higher sea levels, stronger storms, more wildfires. All of these things are a result of the increase in carbon dioxide in the atmosphere.
RW: And yet we heard politicians in a debate this week, extolling the virtues of fossil fuels, which no doubt, have lifted societies up.
MN: Fossil fuels are a modern miracle. Life without it is cold, dark and short. But the fact of the matter is – and if you will – the inconvenient truth is, that carbon that's added into the atmosphere warms up the planet at a rate that is far faster than we saw in any of the major extinctions in prehistoric times. And so we are going to have to deal with this not just as a state, as a nation, but as a world to come together to stop adding more fossil carbon to the atmosphere. That's going to be renewable energy. They talk about carbon sequestration, but the fact of the matter is, if you run the numbers, even at a magical level of $100 per ton to sequester carbon – and we're nowhere near that, technologically – the cost of that would be trillions of dollars to try and put back that carbon into the ground. The fact of the matter is, it's very hard to put the genie back in the bottle.
RW: I'd like to get back to the notion of records. What is the highest temperature ever recorded in Colorado?
MN: Well, if you go to the website for Bennett, Colorado, they will brag that it's 118 degrees. And good on Bennett, it's a nice little town out there; I have friends that live in Bennett. But the state climatologist has looked up all of that and said that's not likely a realistic record, so we will defer to 115 degrees at John Martin Dam on July 20, 2019, beating out a mark of 114 that stood for years at the town of Sedgwick and also in Las Animas. So, the hottest temperature is 115. If you want to contrast that, the coldest is 61 below zero up at Maybell, up in the northwest corner of the state. So, we have a huge contrast and temperature in Colorado.
RW: Will you locate that dam for us, where the highest high was recorded?
MN: John Martin Dam is in the southeast part of the state – southeastern Colorado.
RW: I understand a hail stone fell that would break... well, more than records, if it hit something. You probably heard about this hailstone, Mike Nelson.
MN: I was on the air that day. That was the same day as the Yuma tornado just a couple of weeks ago. And that same supercell thunderstorm produced a massive hailstone that was at 5.25 inches in diameter. But, part of it melted before they could get to a freezer at the National Weather Service office in Goodland, Kansas, and so when they got out to actually measure it, officially – for state records – it came in at 4.6 inches in diameter, which is still really big, but nowhere near the biggest hailstone on record for the United States, which fell in July of 2020 in Vivian, South Dakota, and it was 8 inches in diameter.
RW: Oh! OK, so the largest in Colorado is by no means the largest that has ever fallen.
MN: Not even close. The Vivian one would be the size of my head, but ours is at 5.25 inches.
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RW: A question from a listener near Paonia on the Western Slope. Maryland Stone craves any insight you have into why the skies where she lives are grayer. According to her, it's especially noticeable looking towards the horizon. The Air Quality Index says ozone and particulates are in the green. ‘The only time I can see the iconic blue Colorado Skies is it 9,000 or 10,000 feet.’ What might explain the grayishness?
MN: That's a good question. We have not had a lot of wildfires smoke this year, but we've had some. And across the state, instead of the awful smoke conditions they've had in the Northeast and the Great Lakes, it may be we've had just enough haze this summer from some of the fine particulates from other wildfires in other parts of the country. If not that, it may be that we've snuck back into slight to moderate drought over the southwestern quarter of the state of Colorado and there could be some fine dust particles that are in the atmosphere.
RW: Even when the Air Quality Index is decent?
MN: Yeah, because ozone, of course, is invisible. So when we have an Ozone Alert, we're not seeing anything in our skies, but that still is an air quality issue, which we've had a lot of that along the Front Range this year.
RW: Mike, thank you so much.
MK: Always a pleasure.
RW: Let me ask one more question. Is that okay, Mike?
MK: Yeah.
RW: We've got about a month left of summer to go officially, right? Do these current cooler conditions spell anything for fall? What’s the outlook?
MK: Well, with this massive El Niño that's developing, the warm water in the Pacific, it's kind of a crapshoot as to what's going to happen because the Pacific is a big place; exactly where that pool of warm water sets up, changes how the jet stream flows. Typically, an El Niño fall into winter would bring us chances for maybe a big snow. I mean, the 1997 October blizzard was during an El Niño. The 2003 March blizzard was during an El Niño. So it may be that we'll get one big snowfall this year and typically, El Niño years favor the southwestern part of the state with heavier moisture, as opposed to the northern mountains. Each one is a little bit different, but this one is setting up to be such a big event, and with the changes in climate, most of the experts are saying, ‘We're not really sure.’
Even with the hurricane season, the sea surface temperatures are so warm, they may overcome something that we oftentimes get with El Niño, which is a shear – a wind shear in the atmosphere – that tends to suppress hurricanes. But I noticed that the folks up at CSU at their Tropical Storm Forecast Center – which is weird that we have it here in Colorado, that goes back to Dr. Gray – … the hurricane experts up there have upped their forecast of how many major hurricanes we may have this year.
RW: OK! Thanks, Mike.
MN: Thanks, Ryan. We’ll see you next month.
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