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Issues of the Environment: 2023 was the warmest year on record and could set new record in 2024

Dr. Jonathan Overpeck
University of Michigan School for Environment and Sustainability
Dr. Jonathan Overpeck


  • Taken together, the combination of a strong El Niño event and human-caused climate change made 2023 the warmest year on record by a longshot. According to NOAA, Earth’s average land and ocean surface temperature in 2023 was 2.12 degrees F (1.18 degrees C) above the 20th century average— the highest global temperature among all years in NOAA’s 1850-2023 climate record. It also beats the next warmest year, 2016, by a record-setting margin of 0.27 of a degree F (0.15 of a degree C). 
  • El Niño is a natural phenomenon that occurs when the Pacific Ocean warms more than usual, and it affects weather patterns and global temperatures. "Global temperature in 2023 blew the doors off previous records in many ways. A bigger jump in global warmth than ever before in the global thermometer record, more individual days—hundreds—breaking records than ever before, a warmer ocean than ever before," said Dr. Jonathan Overpeck, Samuel A. Graham Dean and William B. Stapp Collegiate Professor of Environmental Education, School for Environment and Sustainability at the University of Michigan. (Source: *directly quoted* https://news.umich.edu/2023-warmest-year-on-record-u-m-experts-available/)
  • The consequences of 2023’s record-breaking heat were severe and widespread, including extreme heat waves, wildfires, droughts, floods, storms, melting ice, rising sea levels, and biodiversity loss. Scientists warn that unless urgent actions are taken to reduce greenhouse gas emissions, the world will face more dangerous and irreversible impacts of climate change in the future. "The big question right now is what will 2024 bring? The odds favor another exceptionally warm and extreme year of climate disaster. The on-going El Niño is helping to boost global temperature, but it's important to remember that most of the heat humans trap with their emissions of greenhouse gases ends up in the ocean. This is why El Niños tend to release more ocean heat to the atmosphere than in the past. Ultimately, the global temperature records that are becoming more extreme by the decade are driven by human-caused global warming and the impact of this warming on the oceans and El Niño, said Dr. Overpeck. (Source: *directly quoted* https://news.umich.edu/2023-warmest-year-on-record-u-m-experts-available/)


David Fair: This is 89 one WEMU, and despite what you may have felt for a good portion of January, the planet is warmer than it's ever been. In fact, the National Oceanic and Atmospheric Administration has reported 2023 was the warmest year in its 174-year history of measuring the climate. And scientifically speaking, it isn't all that close. I'm David Fair, and welcome to this week's edition of Issues of the Environment. We wanted to find out more about the climate year we've left behind, learn more about its implications and ramifications, and look at what might be in store here in 2024. There's no one better to ask than Doctor Jonathan Overpeck. Doctor Overpeck is a multidisciplinary climate scientist and dean of the School of Environment and Sustainability at the University of Michigan. Very nice to talk with you again, Doctor Overpeck.

Dr. Jonathan Overpeck: Well, it's great to talk with you as well.

David Fair: Were you at all surprised when NOAA reported last year it was hottest on record?

Dr. Jonathan Overpeck: Not at all when it was reported. I think the first half of the year was....I wouldn't have expected that. But then, starting in the summertime, temperatures--global temperatures--just started to go crazy. And month after month, they were way above normal. So, I wasn't surprised by the end of the year that we broke the record.

David Fair: If I've read the numbers right, what we're really talking about is a fraction of one degree warmer than the previous warmest year back in 2016. Now, that doesn't sound like much, but it does set off alarm bells across the scientific community, right?

Dr. Jonathan Overpeck: It sure does. And the real reason for that is not that we broke the record. I mean, it's warming due to human emissions of greenhouse gases, primarily due to fossil fuel burning. The warming is relentless. But what really surprised us was how large the jump was this year. It was the biggest jump we've ever seen. And, you know, some of my colleagues have said things like it was "gobsmacking." You know, to me, it was really not as surprising. We wrote a paper a number of years ago that suggested that these jumps would get bigger.

David Fair: Now, I've heard some trying to explain this away by saying El Nino was particularly strong in 2023. But isn't that at least in part because of the greenhouse gases that get captured and trapped in the oceans?

Dr. Jonathan Overpeck: Well, that's exactly the paper I was referring to. You know, you got to realize that over 90% of the heat that's been trapped by our emissions of greenhouse gases, over 90% of that heat is going into the ocean. So, during an El Nino, it's true. More of that heat stays in the atmosphere. It gets released into the atmosphere from the ocean. But it's heat that's accumulated because of the greenhouse gases. So, the ocean's getting warmer. So, if it releases heat, it's going to be warmer heat. You know, it's going to be warmer.

David Fair: Issues of the Environment continues on 89 one WEMU. And we're talking with Doctor Jonathan Overpeck about 2023 being the warmest year on record. Doctor Overpeck is dean of the School of Environment and Sustainability at the University of Michigan. Now, anyone who has spent any time on social media has probably seen the post that popped up during the most frigid part of the past month, asking, "What happened to global warming?" Well, aren't these kind of more severe weather events, even cold snaps, a real symptom of a warming planet?

Dr. Jonathan Overpeck: Yeah. In the climate science community, we kind of laugh because every winter you hear those kinds of statements, you know? And, for example, one time, a U.S. senator actually, I believe, took a snowball into the halls of Congress to demonstrate that global warming is not happening. And, of course, we still get winter.

David Fair: And ten minutes later, that snowball melted.

Dr. Jonathan Overpeck: Yes. It melts much faster now, as we're seeing with our snow right now. But the point is that one of the impacts of global warming is that it disturbs the atmospheric circulation in the arc way up into the atmosphere. And because of that, you can get more of these cold outbreaks that we used to get. Now, these outbreaks will become less and less cold over time, but nonetheless, when they occur, it's going to feel like real, good old winter.

David Fair: Well, as you've pointed out, one of the ramifications we continue to see is melting sea ice. The measured Antarctic sea ice coverage in 2023 was measured at its lowest level on record. So, the Arctic sea ice ranked in the top ten lowest levels ever recorded, too. Now, that is going to correlate to a rise in ocean levels, as well as a warming planet, right?

Dr. Jonathan Overpeck: Well, the sea ice, when it melts, doesn't raise sea level because the ice is already in the ocean. It's when the ice sheets, like Greenland and Antarctic ice sheets, when they melt, they raise the sea level. And that's happening in a record rate as well. But what the sea ice does do when it melts back further than ever before is it reduces the reflectivity of the planet. And that means more heat gets absorbed from the sun, just as melting more snow causes more heating of the land surface and atmosphere. So, this is what we call a positive feedback or an amplifying effect of the climate system. We lose that whiteness of the surface of the planet, and that accelerates the warming.

David Fair: You mentioned that some of your colleagues described, 2023 as a year in which they were "gobsmacked." How is 2024 shaping up with land surface temperatures and El Nino impacts on ocean surface temperatures? Could 2024 even be warmer?

Dr. Jonathan Overpeck: Yes. You know, one of the reasons the scientific community is scratching our heads is usually when there's an El Nino, it isn't the beginning of the El Nino, the first year of the El Nino, that is record breaking. It's the subsequent year. But this time around, the dominoes started in 2023, and we had the record-size jump in global temperatures in 2023. What's going to happen? And, best estimates, we can predict El Ninos. And it looks as though the current one will continue through the winter and spring and then will die off. We don't know that for sure, but that's the best bet. And so, it'll be very interesting to see what happens to the temperatures. If it was to continue through this year in 2024, we expect record-breaking temperatures almost for sure. But now, we're going to get to see what the effect of the El Nino was most likely if it dies off halfway through the year.

David Fair: This is 89 one WEMU, and our conversation on climate change continues with the dean of the U of M School of Environment and Sustainability, Doctor Jonathan Overpeck. Now, over the years, we keep hearing there is a tipping point from which there is no return. Does your modeling say we are getting rather close to that point?

Dr. Jonathan Overpeck: Well, there are many tipping points, and I think the best way to look at a tipping point is when you cross that point in, say, a certain amount of warming, some things will happen in the climate system that will be irreversible for a long period of time. And a good example of that is the melting of the ice sheets and major sea level rise. The ice sheets take a long time--centuries--to fully come into equilibrium with the atmospheric temperature. But, at some point soon, we're going to reach a point where they're going to want to melt back a lot over ensuing centuries. That would be a tipping point. We're kind of guaranteeing a certain amount of sea level rise. But in terms of the global warming and the weather extremes that we get with the global warming, like the flooding that we get in Detroit and like the drought we're getting in the southwest or the heat waves or the wildfires, all these things are related to the warming. I think what we'll see is a gradual worsening of these until we stop the emissions of greenhouse gases, primarily the CO2, due to fossil fuel burning. When we stop those emissions, then we will have a new climate state that will essentially stay the same for centuries in that warmed state. And that warm state will continue to have the climate extremes that are typical of that state, not100 years ago, unfortunately. So, everything will get worse, and it will stay worse. But the sooner we stop the emissions, it's the sooner we keep things from getting worse.

David Fair: And of course, there are mitigation efforts underway in Washtenaw County, throughout the state of Michigan, various points throughout the country and globe. And mitigation efforts are obviously crucial. But I've mentioned this to you before. I sense that we are not investing enough in adaptation efforts and have the potential to be caught with our proverbial pants down. So, how do you view our progress in adaptive behaviors as we enter potentially another warm record year?

Dr. Jonathan Overpeck: Well, adaptation is really critical, and I think we're doing it in a less kind of big, well-publicized manner. But we are, for example, working in Detroit to reduce the effects of the more intense rainfall that gives rise to flooding. We're working on a number of things in Detroit in their climate action plan. They certainly got that on their radar. So, gradually, we will adapt. I think you see it in our farming and our growing community in the state. They're making adjustments so that they still make money, but the crops still come in. We just have to get better at it. But at some point, even our adaptation efforts--adaptive capacity, if you will--will become overwhelmed by the warming. So, at the same time, it's really good to know that Michigan now has a very aggressive climate action plan in terms of reducing our emissions, switching over to renewable energy and battery storage and electrified cars and trucks. All of this will help keep things from getting so bad that our adaptive capacity gets overwhelmed.

David Fair: I would like to thank you for taking time and sharing your insights today. I'm most grateful.

Dr. Jonathan Overpeck: Well, it's my pleasure. It's always great talking to you, David.

David Fair: That is Doctor Jonathan Overpeck, a multidisciplinary climate scientist and dean of the School of Environmental Sustainability at the University of Michigan. For more information, take a peek at our website at wemu.org. Issues of the Environment is produced in partnership with the office of the Washtenaw County Water Resources Commissioner. I'm David Fair, and this is your community NPR station, 89 one WEMU FM, Ypsilanti.

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Contact David: dfair@emich.edu
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