Scientists issue increasingly dire warnings as ocean surface temperatures spike

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• Geoff Bennett:

  The ocean is rapidly heating up, hitting record-breaking levels.

  The National Oceanic and Atmospheric Administration, better known as NOAA, reported this week that ocean surface temperatures spiked in April and May to the highest levels recorded since the 1950s. This could have dangerous consequences for aquatic life, hurricane activity and global weather patterns.

  To better understand what's happening, Amna spoke recently with

  Kevin Trenberth, a distinguished scholar at the National Center for Atmospheric Research.

• Amna Nawaz:

  Kevin Trenberth, welcome back to the "NewsHour." And thanks for joining us for.

  So, those temperature increases have a lot of folks very concerned. And charts like this one that — this is from a retired math professor named Eliot Jacobson — have gone viral. This one shows mean temperatures from 1982 to 2023 in the North Atlantic Sea. That red line that is way above all the other lines is 2023.

  Should that increase concern us?

  Kevin Trenberth, Climate Scientist, National Center for Atmospheric Research: Oh, indeed.

  And, of course, it's not just the North Atlantic. It's all around the world at the moment.

• Amna Nawaz:

  And tell us why. Why are we seeing those increases? And what should we understand about them?

• Kevin Trenberth:

  We have written reports every year for a number of years now.

  And the oceans as a whole for the top two kilometers of the ocean is — are the warmest on record. 2022 is the warmest year on record. 2021 was the warmest year before that. 2020 was the warmest year before that. So, global warming is clearly happening.

  The other thing which is playing a major role at the moment is that, over the past three years, we have had La Nina conditions, relatively cool conditions from the dateline to the Americas in the Tropical Pacific Ocean. Now we are into El Nino conditions, rather warm conditions.

  There is a pronounced warming off the west coast of South America, Peru and Ecuador, that is disrupting the fisheries and so on there. And it has warmed across all of that sector there, so that the oceans, the sea surface temperature now as a whole is the warmest on record and has been April, May and into June.

  And we're running two-tenths of a degree Celsius above anything prior to that and substantially above the long-term average.

• Amna Nawaz:

  So let's talk about one of the impacts of that. What do those two conditions coming together mean right now as we're moving into hurricane season, in particular, where you have an El Nino event is under way and the warming of the ocean temperatures? What does that mean?

• Kevin Trenberth:

  Yes.

  It means that, along with the general weather that goes on, there are hot spots in the ocean that are becoming increasingly intense and frequent. And those hot spots tend to attract a lot of weather activity above them, convection of different kinds. Small-scale storms, they intensify. Tropical cyclones or hurricanes that are in that area, they move around naturally.

  And so it's a little difficult to say exactly where these spots are going to be. But the fact that they are occurring more and more is a part of this overall global warming signature that we have. And they have real consequences in many ways.

• Amna Nawaz:

  What about the impact of those warmer waters on aquatic life? I'm sure you saw there were some pictures that got a lot of attention recently showing thousands of dead fish washing ashore along the Texas Gulf Coast in recent days.

  How much of that is attributed to those warmer waters?

• Kevin Trenberth:

  Well, with global warming, the — over 90 percent of the excess energy which is being generated every day goes into the oceans.

  And on the — in the oceans, it warms from the top down. And that means there's warm water sitting on top of cold water, which is a very stable configuration. So, one of the things we have been able to document is that the oceans are becoming more stratified. That means that the natural exchanges of air of all kinds, including carbon dioxide and oxygen, going into the ocean are a bit less than they used to be.

  Now, in general, this is overcome by wave actions, so buy all sorts of disturbances in the atmosphere, but in conditions where there are no waves, where there's no wind to speak of. And I believe that's what happened in the Gulf. In the Gulf, it can also be complicated by nutrient runoff, some pollution in the Gulf itself.

  Those conditions come together and create anoxic conditions, no oxygen for the fish. And so you have this big die-off.

• Amna Nawaz:

  And so, Kevin, big picture, when people see these increases in temperatures and it catches their attention, causes concerns, they see global sea and air temperatures are at record highs for this time of year, what should they understand about that?

  How much of that is attributed to climate change? And do we expect that increase to continue?

• Kevin Trenberth:

  The first part of the year is going to hold it down. So 2023 may not quite be the warmest year on record. At the moment, I think that's really held by 2016. But it'll be close. And it could well be.

  But 2024 certainly is looking as though it's going to be the warmest year on record. And part of this is El Nino. But, certainly, the relentless increases in temperatures around the world are related to the global warming problem that we have, to climate change.

• Amna Nawaz:

  And do these increases say to you in any way that the rate of climate change is accelerating? That's the other concern we have heard.

• Kevin Trenberth:

  It is indeed the case that the amount of carbon dioxide in the atmosphere continues to go up, and it continues to go up at close to record levels.

  There's been very little indication that all of the actions that governments and people around the world are taking is really knocking back the amount of emissions of carbon dioxide into the atmosphere. This is really the bottom line as to how the atmosphere is changing. And carbon dioxide is a greenhouse gas. It produces global warming.

• Amna Nawaz:

  That is Kevin Trenberth, distinguished scholar at the National Center for Atmospheric Research, joining us tonight.

  Thank you for your time.

• Kevin Trenberth:

  You're most welcome.