Quotes from Experts

2023’s record-breaking temperatures and climate change

SciLine reaches out to our network of scientific experts and poses commonly asked questions about newsworthy topics.

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This morning Berkeley Earth is releasing its annual Global Temperature Report, and it shows that 2023 was the warmest year on Earth since 1850. How does this report align with other similar assessments?


Robert Kopp, Ph.D.

Well, there are a number of assessments that are coming out right around now towards the end of—right after the end of the year. And they all show that 2023 was extraordinary. It was the warmest year on record. Berkeley Earth says that it was slightly warmer than 1.5 degrees C [above preindustrial levels]. There’s a little bit of variance among the different assessments because they disagree on exactly how cool it was in the late 19th century. But they all agree that this year really jumped out of the record—and extraordinarily warm. (Posted January 12, 2024 | Download Video)

Robert Kopp, Ph.D.
Distinguished professor, department of earth and planetary sciences; director, Megalopolitan Coastal Transformation Hub, Rutgers University

What are your main takeaways from the 2023 Global Temperature Report, and what impacts should Americans expect from these warming trends?


Robert Kopp, Ph.D.

Well, the impacts we should expect are the impacts we’ve seen over the last year, right? If you look through the newspapers of 2023, if you look at the news websites, it has read like a litany of climate disasters: extreme heat waves, intense rainfall and flooding, wildfires, right? These are exactly the changes we expect to see in a warming world, and they’re what we’re seeing in a world that has reached record warmth. So we should view 2023 as a preview of what we might expect to see as years above 1.5 degrees C become increasingly common—and then in the 2030s, the norm. (Posted January 12, 2024 | Download Video)

Robert Kopp, Ph.D.
Distinguished professor, department of earth and planetary sciences; director, Megalopolitan Coastal Transformation Hub, Rutgers University

Is there clear evidence showing that the rate of global warming is increasing, decreasing, or holding steady?


Robert Kopp, Ph.D.

Well, it’s definitely not decreasing, nor would we expect it to until global emissions start going down. It’s still up in the air whether it’s holding steady or increasing. That’s a matter of debate. And it may take a few more years for us to have a conclusive answer on that. On average since 1980 or so we’ve been seeing about two tenths of a degree Celsius per decade of warming. If you just look at the last few years, we might be getting up towards 0.25 or 0.3 degrees Celsius, but we really need more years to say that that’s a trend and not just noise. (Posted January 12, 2024 | Download Video)

Robert Kopp, Ph.D.
Distinguished professor, department of earth and planetary sciences; director, Megalopolitan Coastal Transformation Hub, Rutgers University

To what extent does the Pacific El Niño event explain last year’s record high temperatures?


Robert Kopp, Ph.D.

This was one of the really more interesting parts of the report to me, right? Typically, at least the way I think of it, you’ve got our long-term trend of warming. And then we have superimposed on that high years and low years that to a large extent are driven by El Niño. And that’s the basic story here, too. But the report just points out that we actually started seeing record warmth in the North Atlantic before El Niño started peaking. So there are other things going on that explain the warmth last year, as well—though El Niño is still a large part of that story. (Posted January 12, 2024 | Download Video)

Robert Kopp, Ph.D.
Distinguished professor, department of earth and planetary sciences; director, Megalopolitan Coastal Transformation Hub, Rutgers University

Is the observed spike in North Atlantic temperatures surprising, and how can that be expected to affect the climate in North America?


Robert Kopp, Ph.D.

The North Atlantic experienced extraordinary warmth from the second half of last year. This report assesses it as a sort of once-in-a-century scale event. And I think figuring out exactly the drivers of that is going to be an important area of research in the coming years. So, El Niño contributed to it, but it actually began before the peak of El Niño. Reduced dust from the Sahara perhaps also contributed to it. And reduction in aerosol pollution—sort of a trend over the last few years—may also have contributed to it. And there may be other factors that aren’t as easily explained that we need to understand. This was an extraordinary year. And we do, I believe, expect we’ll see a lot of exciting science over the coming years trying to figure out all the drivers and how they contributed. (Posted January 12, 2024 | Download Video)

Robert Kopp, Ph.D.
Distinguished professor, department of earth and planetary sciences; director, Megalopolitan Coastal Transformation Hub, Rutgers University

Robert Kopp, Ph.D.

Robert Kopp, Ph.D.
Distinguished professor, department of earth and planetary sciences; director, Megalopolitan Coastal Transformation Hub, Rutgers University

Dr. Kopp directs the Megalopolitan Coastal Transformation Hub, a National Science Foundation-funded consortium that advances coastal climate adaptation and the scientific understanding of natural and human coastal climate dynamics. He is also a director of the Climate Impact Lab, a non-profit research organization supporting data-driven approaches to estimating the social and human costs of climate change.