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

This is the third of a five-part series on climate science. Read part 1 here and part 2 here.

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.

But you have to understand that this is really uncertain, because a lot of it depends on ice sheet dynamics. But even at a rate of five millimeters a year – that is, five centimeters a decade or 50 centimeters in a century – we will certainly be able to adapt to that.

JT: The impression people have, though, is that humans have for the first time created a situation where the ice is all melting and the poles are disappearing.

SK: We should distinguish between the sea ice in the Arctic region, the land ice sheet on Greenland and the sea ice around the Antarctic – which comes and goes with the seasons – and the multiple ice sheets on the Antarctic.

We are losing the sea ice in the Arctic, but it’s a highly variable system because it involves winds and currents as well as temperature and sunlight. And I think one needs to look back deeply in the historical and recent geological record to really understand whether this is unusual or not.

JT: In addition to sea level, in your book you devote separate chapters to storms, floods and drought. After reading the book I decided to take a quick look myself at some of the statistics for the United States, which are readily available via the website of the National Oceanic and Atmospheric Administration (NOAA).

There one can obtain time series and graphs for various climate parameters from 1895 to the present. I must say that apart from temperatures – where you can see a clear upward trend – I couldn’t make out any clear trend at all in droughts, hurricanes and precipitation.

Severity of droughts in the US from 1895 until the present as assessed by the so-called Palmer Drought Severity Index. (NOAA)

Hurricane activity in the North Atlantic, 1851-2020, as measured in terms of a combined index of number, strength and duration (NOAA, wikimedia)

SK: You see nothing. You see a little bit in the last couple of decades in California, where it has been getting a little bit drier, but over a couple of centuries that’s not unusual.

Next: Prospects for a ‘red team’ on climate science and how to respond to climate change

Jonathan Tennenbaum received his PhD in mathematics from the University of California in 1973 at age 22. Also an author, linguist and pianist, he is a former editor of FUSION magazine. He lives in Berlin and travels frequently to Asia and elsewhere, consulting on economics, science and technology.