I said in my last essay that I would return this week to another theme that is having a big revival just at the moment, post the USA withdrawal from the Paris Accord. This one is ‘rising sea levels’. It was one of the dooms forecast in the NYT Mag article I referred to last time: Barring a radical reduction of emissions, we will see at least four feet of sea-level rise and possibly ten by the end of the century. I can only shake my head in wonderment at claims like this one. Has there been a dramatic increase in sea levels somewhere? No. Has there been a stunning new paper published somewhere whose message should fill us with terror? No. It’s just another scary story. I came across the sea-levels theme in a number of places, but the most useful one for readers is Larry Kummer’s ‘Fabius Maximus’ site that I have referred to on a few occasions.
I choose it because it has many useful links. Larry Kummer writes: As so many of the predicted effects of climate change have failed to appear on time (e.g., the end of winter, more and stronger hurricanes), rising sea levels have become the focus of climate activists. It creates easy (if unscientific, even daft) graphics of global flooding — hopefully panicking insurance companies and landowners. Unfortunately, as so often the case, the science has not supported their screams of “Wolf!”
Now a new cycle begins, with the first salvo being Jeff Tollefson’s “Satellite snafu masked true sea-level rise for decades” in Nature, 17 July 2017 — “Revised tallies confirm that the rate of sea-level rise is accelerating as the Earth warms and ice sheets thaw.” A mild tone, as such articles go.
Roy Spencer was scornful of the way the Nature story was written up by the mainstream media: I’m calling “fake science news” on the Nature reporter who covered the story… The researchers in April made a major adjustment to the first 1/4 of the satellite record, bringing those early sea levels up. This results in adding curvature to the upward trend (an acceleration) by flattening out the early part of the curve. This new signature of “acceleration” was what made the news in the new Nature study, even though the long term trend went down.
In short, the effect of the change was not that sea-level rise was accelerating but that the long-term trend was revised downwards, almost the opposite of the headline message. Roy Spencer had a nice dig at the headline writer, pointing out that anyone can write a headline that is not technically incorrect but carries a unwarranted doom-laden message: ‘Scientists agree. Sea-levels are rising. We are all going to die.’
James Hansen, the putative father of the CAGW scare, came out with his own take on sea-levels in the same week. Here is a bit of it:
I don’t think we’re going to get four or five degrees this century, because we get a cooling effect from the melting ice. But the biggest effect will be that melting ice. In my opinion that’s the big thing — sea-level rise. Because we have such a large fraction of people on coastlines — more than half of the large cities in the world are on coastlines. The economic implications of that, and the migrations and the social effects of migrations — the planet could become practically ungovernable, it seems to me.
But of course no one with any sense or knowledge of the data is talking about a four or five degree rise in temperature by the end of the century, and where we get a cooling effect from melting ice I don’t think anyone knows. We still have to see a single climate change migrant, despite the millions of them there were going to be arriving somewhere in 2010, and the 150 to 300 million expected in 2050. All in all, this Hansen quotation shows a man who just likes sounding off.
- The seas are slowly rising and may continue to do so. They have been rising slowly for thousands of years. If the IPCC is right (AR5) there will be an increase in Global Mean Sea Level of about 25 cm by the end of the century. This is well within the adaptive capacity of nations. (The rise around Sydney under these circumstances seems likely to be around 10 cm. It will be hard for my elderly great-grandchildren to notice.)
- Perhaps the rate of increase in sea levels is increasing; perhaps it is not. There’s lots of natural variation, and what is being measured (‘the signal’) is very small and hard to separate from noise.
- If the world continues to warm, sea-level rise may rise a little more quickly, through thermal expansion and some melting of land-ice.
- Those consumed by alarm about global warming will continue to exaggerate all of this.
If you read past Larry Kummer’s options you will find several charts and links to support these conclusions. Read them all, and you are likely to come away with the view that the whole thing is hugely uncertain, and there is no immediate or even short-term (fifty years or so) problem.
And people like me scratch their heads and ask, Why are we doing all this? Why are we trying to reconcile tidal gauge and satellite observations? Most tide gauges are on mainland sites, for good and obvi0us reasons. Why are we trying to establish a Global Mean Sea Level? It all sounds like trying to establish a Global Mean Temperature. In the case of temperature, I keep arguing that the only purpose for doing so is to be able to suggest that there is a trend, that the earth is warming, and by implication that we humans are responsible. To say it once again, I have no great difficulty with the notion that the earth is warming, though on the admittedly rubbery evidence, there hasn’t been much since 1850, and a warmer planet is for virtually all life forms better than a colder one.
So what is the point of a Global Mean Sea Level? I think the explanation is similar. If it is possible to show that that the seas are rising, then it will be possible to show that a continuation of this trend will cause problems for someone at some future time, and possible therefore for alarmists to cry ‘We are guilty!’ I’ve written about this before, as here.
The problem with both these averages is that they mean nothing to anyone. We live with local, not global, weather and sea conditions. If you want to know what will happen to your seaside property in the NSW central coast, the best indicator is the Fort Denison tide gauge in Sydney, which has been running for nearly a century and a half, and shows an increase of a little less than 1 millimetre a year, or about 10 cm a century. Sydney is stable geologically. Fremantle and Auckland will give you comparable sea-level rises. Go to the north-west of Western Australia, on the other hand, and you’ll find much larger sea-level rises, partly because of geostatic changes (movements in the earth’s crust). The Baseline Sea-Level Monitoring Project shows the diverse variations around Australia.
Coincidentally, I was at a dinner to mark the thirtieth anniversary of the abolition of the department of Science (in July 1987, caused by the Hawke government’s consolidation of 39 departments into 15 super departments). The guests were all scientists and scientific managers, plus one former Minister (Barry Jones). It was a good dinner and an enjoyable evening. One of my dining companions, whom I had not met before, raised the subject of sea-level rises, and suggested that I was not up with the latest findings about reconciling tide-gauge with satellite measurements, and thus reconstructing an approximation for 20th century sea-level rises.
It was the wrong place and time to have a discussion, but he kindly sent me two papers, both of which I’ve now read. The first, by Hamlington and Thompson, sets out a rationale for using tide gauges: If the focus is on estimating the 20th century trend in GMSL, the set of tide gauges employed should largely consist of long records that are relatively unaffected by (or that can be reliably corrected for) vertical land motion. If you are interested in regional trends and variability, you can use tide gauges with shorter life spans, but beware of land movements. I thought it a good paper, more accessible than many in this field. And I agree with the recommendations.
The second, by Jevrejeva, Matthews and Slangen is behind a pay-wall, but I am happy to forward a copy to any reader interested. This paper starts with a straightforward alarmist assumption: For delicate coastal ecosystems, small islands and fast-growing coastal cities (Hallegateet al. 2013; Jevrejeva et al. 2014), sea level rise is one of the most dangerous aspects of climate change (IPCC 2013). Global sea level rise is an integral measure of warming climate (Munk 2002; Church et al. 2013; Jevrejeva et al. 2010), reflecting alterations in the dynamics and thermodynamics of the atmosphere, ocean and cryosphere as a response to changes in radiative forcing.
Stating as a fact what has yet to be proved is not a promising start, but we can move on to the point of the paper, determining a sea-level ‘budget’ for the 20th century. A great deal of data produces what to me seems another finding where the uncertainties are greater than the signal. No one doubts that the seas have been rising slowly. They have been doing so for a long time. The real question is whether they are rising now in an unprecedented way, and whether anyone should worry about it. Both these papers contribute to the question, but neither of them provides a definitive answer.
And I ask again: why are we doing this? For those who do all this, of course, the reason is straightforward. Here are Jevrejeva and colleagues: It might never be possible to determine contributions from sea level components to the twentieth-century sea level rise to the same accuracy as has been archived for the past 10–20 years. However, it remains important to understand better the magnitude and uncertainties of the physical processes that contributed to sea level rise and variability during the twentieth century.
Why is does it remain important for anyone else? That is the question.