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Brian Lehrer: Brian Lehrer on WNYC. Now, our climate story of the week, which we do every Tuesday on the show, on a day when it's considered possible that one place in the United States might break the all-time heat record for anywhere on Earth. Have you heard this? A high temperature of 128 degrees was recorded on Saturday and Sunday at Death Valley National Park in Eastern California.

One visitor on a motorcycle died Saturday from heat exposure, or he was there on a motorcycle trip, and another person was hospitalized. By some estimates, 130 is the hottest temperature ever recorded on Earth a few years ago, also in Death Valley, and they may hit that again today. Meanwhile, in Texas, Hurricane Beryl made landfall in Southern Texas and Louisiana.

At its peak, that hurricane was a record-shattering Category 5 storm, but has since been reduced, thankfully, as it hit land to a far less powerful tropical depression. At its peak, the reason it was said to have broken a record is that, it was the strongest hurricane in history for this early in the hurricane season, another indication of global warming. Beryl became the first storm in the Atlantic hurricane season to make landfall in the US after tearing through the Caribbean.

The National Weather Service has also issued heat advisories for today through tomorrow for most of our Greater New York City area. All of this is going on, and I know weather does not equal climate, but when there is weather in certain patterns, it does. It at least indicates climate. Let's talk about that relationship in these instances. Joining us now to discuss is Bob Henson, meteorologist, journalist and regular contributor to Yale Climate Connections. Bob, hi. Welcome back to WNYC.

Bob Henson: Hi, Brian. Great to be back here with you.

Brian Lehrer: Let's talk about the all-time high temperature recorded on Earth. I read one version that said it was 134 at one time. I guess meteorologists can disagree on what was read, where and when. The other version that I read was 130 just a few years ago. I think it was 2021, so certainly in the global warming era, in Death Valley. I wonder if you have a stat that you go by, as the possibility of hitting 130 looms out there this week?

Bob Henson: I certainly do. It's a great question. As you point out, there are different numbers floating around out there. For many years, and certainly growing up in the almanacs I read as a kid, the record was 136 degrees. That was set in Libya close to a century ago. Well, after investigation a few years back, it turned out that was observed during non-standard conditions.

The thermometer wasn't cited properly, and it was apparent that the environment probably goosed that temperature. That was essentially dethroned by the World Meteorological Organization. Then, they reverted to the next highest, which was the 134 in Death Valley recorded back in 1913. Now, that one has also been thrown into doubt by one of the same people who investigated the Libya record.

It looks unlikely that even that 134 is accurate, although the World Meteorological Organization, which is the arbiter of these records, still has it as the official world high. There are a couple answers, but basically, I and most of my friends who are into weather records, use the 130 degrees in 2021 at Death Valley as the reliable world record.

Brian Lehrer: Is this climate, or is this just weather?

Bob Henson: It's both. As you point out, there's always some mix of the two. A weather event like a single tornado is pretty much weather. Tornado patterns, in terms of where they happen, can shift, and are shifting, but we're not getting more intense tornadoes because of climate change. Heat is another matter. If you turn up the burners, you're going to get more bubbling on the stove.

Certainly, the heat wave in the west right now is unprecedented in several places, including duration. For example, Las Vegas even topped the number you gave on Sunday, getting up to 120, which is three degrees above their all-time high. They're going to be back up to 117, 118 the next several days. Their longest stretch of 115-degree weather on by far. Death Valley will be up close to 130. I don't think they're going to get there today. They may not even get there this week, but several days of 127, 128 is bad enough.

Brian Lehrer: Yes, really. When you look at long-term patterns in conjunction with a 100th anniversary of the station, which we're observing these days, I was looking back at some weather records, because in our 100 Years of 100 Things series will do 100 years of global temperatures at some point. It looked to me, from the chart I was reading, that the average high temperature in July in New York City, 100 years ago, was in the low 80s, now, it's in the high 80s. Does that sound right to you?

Bob Henson: That does sound right. Let's not neglect New York City this summer, because you're already basically having the fourth hottest summer on record so far. It's moving up in the charts, as it were. The warmest summer on record was 1966, and some of your listeners may remember the song Summer in the City, which came out that very summer, and really captured probably how it felt that summer. There's a chance this year will be--[crosstalk]

Brian Lehrer: When we hear records like that, "This is the hottest summer since 1966, the hottest summer since 1917," that makes me question the climate change connection, because we didn't have-- Certainly, we had a lot of fossil fuel use in 1966, but not the accumulation of it over all the decades that we have to this point. If 1966 was the hottest summer on record in New York City, and not 2020, and 2021, and 2022, what does that tell us?

Bob Henson: Well, the difference is, you have to look at larger areas to see the signal of global change emerge more prominently. If you just pick one city, any number of things could give that city their all-time high 30 or 60 years ago, but when you look at the whole country, the hottest summer on record is a tie, a very interesting tie between 1936 and 2021.

1936 was the Dust Bowl. You had denuded landscapes all across the Central US. Overplowing, that allowed the land to heat up, and reinforced a naturally-occurring multi-year drought. Many of the records from the '30s are still there. This gets brought up a lot by climate skeptics and dismissers, but that was a human-caused climate change of a very different sort. Things settled down, and then we're back up to those levels of heat now nationally.

Now, individual state, or local records in the '30s are still there in a lot of places, but a lot of them have tumbled. The hottest day in New York City's history was this very day in 1936, a hottest month in US history. That was 106. New York City has never gotten above 104 in any other day, but there's a lot more 90s and temperatures approaching 100 now, and a lot more warm nights than you ever used to have. You're probably going to be 75, or warmer at night this entire week.

Brian Lehrer: Not to confuse what should be a relatively clear statement of fact, we are seeing the record warmest years on Earth, basically, year-after-year since 2000. The big picture trend line is obviously clear. The Earth is warming. We are in our climate story of the week, which we're doing every Tuesday on the show this year with Bob Henson, meteorologist, journalist and regular contributor to Yale Climate Connections.

We can take a few phone calls for him on the connection between the extreme weather events we're seeing right now in the United States, and climate change. We've been talking about the possible hottest temperature ever recorded on Earth potentially happening this week in Death Valley. We're going to move on to Hurricane Beryl, and how that relates.

Listeners, if you have a question or a comment, we can take a few at 212-433-WNYC. Call or text 212-433-9692. You've been writing about Beryl, in terms of it barreling its way, as you put it, through numerous records. Give us a few.

Bob Henson: Well, it was by far the earliest Category 4 hurricane in the Atlantic, the earliest Category 5. Just was something you would expect in August or September, not in early July. We know that's because the ocean temperatures have been at record highs in the North Atlantic, essentially, for the last year. There's a heck of a lot of accumulated heat in the Caribbean, and the Gulf of Mexico, and the tropical open North Atlantic.

Beryl took advantage of all that heat, and actually managed to overpower the wind shear that's almost always in place in the Caribbean in early July. You don't tend to get major hurricanes in the Caribbean in July, because it's a little too early in the season. There's not as much heat as there usually is later on, and also just the climatology of how trade winds work at that time of year, just tends to not favor the air motions you need to make a hurricane.

Well, Beryl just shot through all that wind shear because there was so much oceanic heat, and it was able to build the thunderstorms to keep it going, and interestingly, even though it hit the Houston area on Monday as a Category 1 storm, it didn't get much press. This morning there's still 2.2 million people without power in the Houston area.

Brian Lehrer: Oh, yes. I had not heard that.

Bob Henson: That's not good when you're under an excessive heat warning, or watch rather.

Brian Lehrer: Right. Yes, let me take you back to one of the facts that you mentioned, because I think it's interesting basic science to go over for some people. What makes a strong hurricane? You're saying, it has something to do with how warm the waters are. There, again, we get that the explicit link between the warming of the earth, and the strength of the storm. Can you talk about that scientific relationship, and again, the trend lines over time?

Bob Henson: That's exactly right. A hurricane needs fuel, and then it needs a spark, and you could think of that as a rough analogy to forest fires. You know if you have a hot dry summer, you're more at risk of a wildfire, but you're not guaranteed of getting one. It just depends on whether there's a lightning strike, or someone throwing a cigarette out a window. You need the trigger, as well as the preconditions.

We knew going into this hurricane season that the preconditions were off the charts, and the seasonal forecast you've probably seen calling for record activity in the Atlantic, are based on that. Still in all, you don't know exactly when, or where you're going to get any individual hurricane, and that comes down to these seeds, or disturbances [00:11:48] in the atmosphere.

Once those develop and pass over the incredibly warm water, then they have a chance to go. That's what we saw. One of the seeds came across, and normally in early July that seed might not do very much, but in this case, it was able to draw on those record warm waters, and we're off to the races.

Brian Lehrer: Here's a stat from the BBC. Every day since late March 2023, global ocean surface temperatures have set new records for the hottest temperature ever recorded on that date. I'm just going to say that again, because it's self-explanatory, but it goes by quick. Every day since late March 2023, global ocean surface temperatures have set new records for the hottest temperature ever recorded on that date.

That's an example of why there's major consensus within the scientific community that the oceans are getting hotter over time, and then you connect that, presumably, to rising greenhouse gas emissions, right?

Bob Henson: Yes, that's more like an inference, but an obvious inference. [chuckles] We've got heat-trapping gases.

Brian Lehrer: Because what's the alternative explanation?

Bob Henson: Right. There's no other explanation that makes sense. You'd also have to discount the tens of billions of tons of CO2 we put up there. Now, an important point is that, we're not necessarily going to get more hurricanes. The Atlantic has been on an upward trend, other oceans haven't necessarily. In fact, this year's been very, very quiet in the Pacific, just strangely quiet.

Typically, the oceans around the world trade off, one is busy in one year, and the other is quieter in that year. When you do get the hurricanes, it's the warm waters allow them to be stronger. What we're seeing across the world is a higher proportion of the hurricanes that do form are becoming these Cat 3s, Cat 4s, Cat 5s.

Brian Lehrer: Andreas in Manhattan, you're on WNYC. Hi, there.

Andreas: Hi, thanks for taking my call. I'm just curious, the temperature at which the body can no longer cool itself down, is that 137? Because I assume we'll probably reach that in numerous places around the world, eventually, and we'll see mass extinction capabilities.

Bob Henson: Yes. Well, it's actually really, really difficult to get to a temperature where you literally can't survive, what's called the unsurvivability factor, and that's a combination usually of heat and humidity. If you can be in the shade, then it's much easier to survive what they would call dry heat. If you don't have access to shade, then it's much more difficult. If the humidity is high, then it's just difficult to get through it. There's a [unintelligible 00:14:37] more esoteric ways to measure temperature, WetBulb Globe Temperature, and so forth.

The bottom line is really that unsurvivability threshold is only met literally for hours, a few hours at a time, in extremely limited parts of the globe, near the Persian Gulf is the most common place. So far, we haven't seen massive death tolls associated with those very, very brief instances. Now, research shows those instances will become more common. They're still not going to be anywhere near the heat concerns, and heat deaths caused by more garden variety heat waves.

That those are just going to get worse, and they don't have to be anywhere near that "unsurvivable" level to kill people. I think there needs to be a lot of attention to those more frequent, you might even call garden variety heat waves that are taking lives right now. Phoenix just had the deadliest June on record for heat deaths. I think it was 175 people.

Brian Lehrer: Listener texts, "One problem with records like these, like temperature, is that it sounds exciting that we've hit a new high. Can you ask your guest how he can take the thrill factor out of these alarming trends?"

Bob Henson: That's an excellent question, and I'm guilty of this, and it goes back to growing up in Oklahoma. Tornadoes and severe weather are what got me interested in weather and climate in the first place, and for a long time I've dealt with this ambivalence inside about being excited and fascinated by a tornado, but horrified by the damage it can do. I came into writing about weather and climate from that perspective.

There is a sports reporting, stenography aspect to climate coverage, and we're quite aware of that. That doesn't take away one bit from the awfulness of climate change, and the human agency in it, and the many effects, especially, on people who didn't cause it. I think we try to hold both in our heads at the same time that it's important to count the stats, and figure out what's happening, but to be compassionate at the same time, and forward thinking, and always keep in mind that this is something that affects people and ecosystems. It's not just a numbers game. Thank you for that point. It's a really good point.

Brian Lehrer: Tom on Staten Island has a question about understanding the stats too. Tom, you're on WNYC. Thank you for calling in.

Tom: Thank you, Brian, for everything you do every day. Weather climate guy, thank you for what you do. Question. To get some of these temperatures, whether it be ocean, country, et cetera, about, let's say our country, and let's say the water for the world, for the country. About how many data points might you use? It could be an about answer. The same for the oceans of the world. About how many data points? Any ideas?

Bob Henson: Sure. That's a great question. I wish I could calculate it right off the top of my head. What I can tell you is that, there are thousands and thousands of weather stations around the globe that observe in a pretty formalized way, going every hour at least. Often, human beings taking the measurements, sometimes automated instruments, but these are all under protocols established by the World Meteorological Organization. That's a well-working system. It's been in place for more than 100 years.

Now, in more recent decades, computer models have been able to do what's called reanalyses, where they go through and fill in the gaps, essentially, and use interpolations and such to figure out what the temperatures are in those places where we don't have a weather station. The resolution of those reanalyses varies. I think it's usually on the order of maybe several tens of miles. You could take that and divide the diameter of circumference of the world by that, and come up with a number. It's many thousands of grid points.

Brian Lehrer: Right.

Bob Henson: Over the oceans, it's a combination of satellite-observed ocean temperature, which can be used as a proxy, because the ocean smooths out air temperature changes. Also, buoys are dipped into the ocean, and those directly measure ocean temperature. It's a great question. In my book, The Thinking Person's Guide to Climate Change, I have a whole chapter on how global temperature is assessed. It really is interesting.

There's a lot of science that goes into it, and a lot of care to factor out things like urban heat islands, because those are real. The fact that it's hotter in New York City because it's more built up is it's not fake. It's a real thing, but it's not the same as global climate change. Those are factored out.

Brian Lehrer: Yes, I'm glad he asked that question and that you put it in those terms, because it's one of the things that we have to guard against, if we're going to take climate seriously, that is not to be so reductionist, that we jump on shows like this, or elsewhere in the press, or in scientific circles to saying, "Oh, it's going to be 130 for the first time ever in Death Valley this week, potentially, therefore, climate change."

We have to look at the trends over time, and over a lot of time, and over a lot of data points, and we try to stick to that standard, but it's good to articulate that. One more call from Izzy in the Bronx, who says he's a retired meteorologist. Hi, Izzy.

Izzy: Hi, how are you doing? Can you hear me now?

Brian Lehrer: Yes, we got you.

Izzy: Hello. My comment was I had read in the literature recently about the lowering of gradients between the poles and the equator. That causes longer-term blockages. Our atmosphere is not moving as quickly as possible, so you get the trends where you're getting heat for a very long time in one location, cooling on the other side. Something like an omega block that doesn't want to unomega itself.

Also, in the winter, you get areas that are potentially becoming colder, and staying colder. I don't know if you've read anything about that, and if that is being data. Do you have any comments about that? [crosstalk]

Brian Lehrer: Do you understand the idea there, Bob?

Bob Henson: Yes. This has been a topic of research, I'd say for about 10, 15 years now with an increasing interest in it. There were some big papers in the early 2010s, by Jennifer Francis, Steven Vavrus, a couple of other researchers finding this weather weirding effect of, potentially, less than temperature gradients between Arctic and tropics, allowing for the jet stream to get more wavy and wonky, and were blocking highs, or strengthen up the lows to just sit there.

They didn't find some evidence. This could be happening in the winter, and we connect to so-called polar vortex episodes. There's been other work pushing back on that and saying, "Well, if you actually look over the long term that your instances of record cold are simply on the increase, so whether or not we're having those episodes." It could be a mix of both that when we get the occasional epic, cold wave like Texas had in 2021, it could be in part because of that blockage. Perhaps, exacerbated by the temperature gradient issue you cited but--

Brian Lehrer: I wish we had more time, but--

Bob Henson: I'm sorry. [crosstalk]

Brian Lehrer: In our last 30 seconds, if people are hearing that as, "Wait, global warming can cause record cold?" Can you give a 30-second quick explanation? Maybe we'll come back and do it in more detail another day.

Bob Henson: I would say the jury's still out on that one. It's interesting research, but we do know that the weather patterns are getting stuck. It's a difficult thing to analyze, but there's evidence in the summertime for resonant patterns that are similar to this, but I'd say, I'm a little more concerned about heavy rain events stalling, than I am about winter cold waves increasing. I think, really, it's heat we've got to worry about going forward.

Brian Lehrer: Bob Henson, meteorologist, journalist, regular contributor to Yale Climate Connections. You mentioned your book title, which I didn't have, so why don't you plug your book on the way out?

Bob Henson: Sure. It's The Thinking Person's Guide to Climate Change published by the American Meteorological Society available on Amazon. It was originally called The Rough Guide to Climate Change, but it's been reworked in a new title.

Brian Lehrer: Thank you very much.

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