Are Sea Levels Rising?


The UN secretary general has warned the planet is close to “the point of no return” and branded global efforts to combat climate change “utterly inadequate”, as world leaders gather for a vital conference on the Paris Agreement.

Antonio Guterres issued the stark warning ahead of the fortnight-long UN climate change conference (COP25) in Madrid.

Rulers and delegates from almost 200 countries will attempt to firm up the commitments made in 2015, establish new international rules for emissions trading, and broker systems of compensation for poorer countries already affected by global warming.

 The Alliance of Small Island States, representing nations most at risk from rising seas, views the talks as the last chance to avert potential “catastrophe”, while Save the Children warns 33 million African children are facing hunger as a result of cyclones and droughts made more likely by climate change.

Never heard of the Alliance of Small Island States. Are they really at risk from rising seas?

It’s only been a couple of days since I remembered the smallest and most low-lying island I ever set foot on: the Isla dos Amores in Rio de Janeiro’s Guanabara bay. If sea levels have been rising all over the world, as a result of melting ice sheets in Greenland and Antarctica, then the Isla dos Amores should surely have disappeared by now, because sea levels would have risen in Guanabara bay just like everywhere else. Or it would at least have shrunk in size a bit as the water rose. But, if anything, the Isla seemed to be slightly bigger than the day I set foot on it back in 1958, over 61 years ago.

I suppose that a climate alarmist might say that, actually, sea levels in Guanabara bay can’t rise very much, because Guanabara bay, like the San Francisco bay in the USA, has a narrow entrance through which sea water flows slowly, effectively insulating it from tidal swings in the ocean outside the bay. He might add that sea levels don’t rise the same amount everywhere, and cite cases where islands have actually disappeared beneath the rising sea. He might add that you need to study lots of islands, and not just one. But could he name an island that has disappeared beneath the rising sea?

A remote Hawaiian island has totally disappeared overnight – two decades before scientists predicted. East Island was an 11-acre strip of gravel and sand in the north west of the Hawaiian archipelago. Now it’s beneath the sea, washed away by a hurricane.

Is being washed away by a hurricane an example of rising sea levels? I don’t think it is. Hurricanes cause storm surges that can raise sea levels locally by several metres as they pass through. But after the hurricanes have left, sea levels return to their former levels. And furthermore low-lying islands that are just sand and gravel can probably easily be swept away by storm surges flowing over them. And many Pacific islands are just low-lying sand and gravel. But there are more, as the Guardian hastens to point out:

Five tiny Pacific islands have disappeared due to rising seas and erosion, a discovery thought to be the first scientific confirmation of the impact of climate change on coastlines in the Pacific, according to Australian researchers.

Only the Guardian doesn’t point out the line in the associated report that says:

However, the limited research on reef islands in the western Pacific indicates the majority of shoreline changes and inundation to date result from extreme events, seawalls and inappropriate development rather than sea-level rise alone.

But wait! Forbes has got eight islands that have vanished:

Need a reason to be concerned about rising sea level? I’ve got eight. A recent study found that at least eight islands in the Pacific Ocean have disappeared due to rising sea levels. This is a trend that has continued for several decades, with low-lying, often coral atoll islands being submerged by rising seas.

A recent study documented the effect of sea level rise, which averages 3 mm per year globally and up to 12 mm per year in the western Pacific in recent decades. The team found that islands in Micronesia have disappeared in recent years with little to no evidence they existed at all. Several Solomon Islands had similar fates in recent decades as they were overtaken by the sea.

Do they mean that there is little or no evidence that some of these islands ever existed at all? Perhaps they didn’t. Perhaps they were geographical errors, accidental ink blots that were given names.

But some numbers at last. If sea levels have been rising on average by 3 mm per year, and 61 x 3 = 183 mm = 18.3 cm. No wonder the Isla dos Amores hasn’t disappeared.

Guanabara bay was also a port. So are port authorities worried about rising sea levels? Not Vancouver, it would seem:

Vancouver Fraser Port Authority defends itself

The sticking point is around the terminal’s preliminary design, which forecasts the local sea level to rise by 50 cm by 2100. “Sea level rise is not expected to adversely affect the project over the long term,” reads the planning document.

Yet, according to storm simulations conducted by Canadian newspaper The Globe and Mail, if hit by a one-in-500-year storm, much of the port’s facilities would be severely impacted. Throw into the mix a 1 m sea level rise expected by 2100, and most of the port would find itself underwater, claims the study.

If sea levels are rising by 3 mm per year, Vancouver might expect a 30 cm sea level rise by 2100. So if they’re planning on a 50 cm rise, they’re factoring in a sea level rise of nearly double that.

Add to all that the fact that sea levels have already risen 60 metres over the past 12,000+ years, and there’s nothing new about it at all. So why the big fuss about it now?

Furthermore, the past 12,000 years have been an interglacial warm period in Earth’s history. If the ice returns, we’ll start seeing sea levels fall, as it gets locked up in new ice sheets. I wonder if Vancouver Port Authority factored that in as well?

About Frank Davis

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3 Responses to Are Sea Levels Rising?

  1. Furtive Ferret says:

    Interesting piece here from Anthony Watts’ blog:
    I read it at the time of publication and thought it very germane to this posting.

  2. Philip Neal says:

    Years ago, also on What’s Up With That, Willis Eschenbach observed that coral atolls are “floating islands” and in no danger of being drowned by rising sea levels because, as Darwin first realised, living corals grow upwards towards the sea surface as the rubble of old, dead coral sinks beneath them.

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