Rising sea levels no cause for climate change alarm

Former US Energy Department chief scientist Steven Koonin says sea levels rise at changing rates and sees ‘no signs’ of a climate apocalypse

Melting iceberg with ice floe in foreground, floating in the sea off Antarctica. Photo: AFP / Photostock-Israel / Science Photo Library

Here we continue our interview with Dr Steven Koonin, chief scientist in the US Department of Energy during the Barack Obama administration and author of the just-published book, Unsettled: What Climate Science Tells Us, What It Doesn’t, And Why It Matters.

JT: The media and NGOs have propagated the notion of that we are facing a climate disaster of apocalyptic dimension, time is running out and we need to declare a global state of emergency. What would you say to somebody who has this idea that we’re facing an apocalypse?

SK: What I would say is, the models show no signs of apocalypse. A lot of the bad things that people talk about just have not been happening, and the quantitative projections that are in the reports explicitly say this is not a big deal.

In fact, one of the key findings is climate is only one, and a relatively minor, factor in determining economic well-being. It’s right there in the report. So I don’t understand why people think this is going to be a disaster.

JT: Well, one effect, which is very much up front in the media and in people’s minds, is sea level rise. People are used to seeing pictures in television of masses of ice breaking off from glaciers and falling into the ocean. This is really horrifying. What do you say about that?

SK: Well there is both a quantitative and a qualitative issue. Let me start with a quantitative issue first. As I talk about in the book, global sea level rise is not easy to measure. Data on local sea rise is a lot better. But if you look at the rate of global sea level rise, as well as we have been able to measure  over the last century, it’s got ups and downs.

JT: For many ordinary people, just to hear that the sea levels are rising at all is enough to terrify them. Popular media coverage of global warming often leaves the impression that sea level rise per se is something new and caused by humans.

And yet it is well known that sea levels have been rising more or less continuously for the last 20,000 years, since the last ice age. Sea rise is nothing new, nor is large-scale melting of continental and polar ice.

Everyone ought to have learned that in school. In your book you note that the rate of sea level rise varies quite a bit. What has been happening in the recent period? Are there signs that the rise is accelerating?

SK: If you go back to 1940 or so, global sea level was going up two and a half millimeters a year. And then if you go to 1960 it was going up only one millimeter per year. The rate went down tremendously. And then it went back up again; currently it’s at about three millimeters a year, just a bit higher than it was in 1940.

Eighteen-year leading trends in rate of Global Mean Sea Level rise since 1900. Estimates from three different tide gauge analyses are shown, together with a single value from satellite altimetry. (Courtesy Steve Koonin)

We’ve got a good deal of natural variability in the records that we have, and we are only just beginning to understand why it did that. Greenland ice 70-80 years ago was melting agt about the same rate as – or even faster than – it is now. So, we have got to untangle the natural variability before we get really excited about what we’ve seen over the last 30 years.

If you look at the example in the book of sea level as recorded by the tide gauge at the Battery – the tip of Manhattan – it has got very clear oscillations in the rate of rise.

Thirty-year trailing trends in the sea level rise at The Battery, Manhatten from 1923 to 2020. The horizontal line indicates the average rate of 3.02 mm per year. (Courtesy Steven Koonin)

It’s really hard to judge what the cause is because although human influences have been growing during that trend, you see this very strong oscillatory behavior, which says that natural variability is playing an important role here.

Now, that said, it’s clear that the warming of the planet will lead to less ice and therefore a higher sea level. But according to the IPCC projections of what the rate of rise will be – it’s different in different places – you know, we might see another 30 centimeters by the end of the century or equivalently the rate would go from the current average of three millimeters to something like four millimeters per year. But we don’t see that yet.

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May 12, 2021 at 04:24AM

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