Do You Need to Worry about Rising Sea Levels?

People are getting very worried about rising sea levels. Local governments are discussing “planned retreat” for coastal settlements, and owners of beach houses are worried about losing insurance cover and ending up with million-dollar views they can’t sell.

Do you need to panic? Here’s a few things to consider.

The sea level has been rising in New Zealand, where I live, at an average of 1.8 mm per year over the last 120 years. That’s close to the global average. To picture that amount clearly, it’s about the width of a grain of rice every year.

Next time you’re at the beach, watching the waves crashing onto the shore, think about a grain of rice.

 

“Oh,” you say, “but it all adds up. My father’s friend, Jed, says the sea is coming up all around his beach house, and he says it wasn’t like that 30 years ago.”

It’s very nasty to experience the sea’s inevitable encroachment, but let’s remain calm and focus. Thirty years at 1.8 mm a year is 54 mm. That’s about the size of a chicken egg.

So the next time you see Jed, ask him if he thinks the sea level has risen more than the length of an egg. If he says, “Are you crazy? Of course it has! It must have risen a good half metre,” then you can assure him it’s not due to general sea-level rise. A rise of half a metre, or 500 mm, would take 277 years at the average rate, meaning he must have been checking the water level at his beach house from long before any European settlers arrived.

“Oh, but I’ve heard it’s sped up lately,” you say. “I read (maybe here) that the global average rise accelerated to 2.5 times faster from 2006 to 2015. And in New Zealand, between 1961 and 2018, the rate of rise was almost double the average. So it’s speeding up.”

OK. What do you think is causing it to speed up? I ask.

“Global warming, dummy,” you say.

There are problems with this argument. First, there is dispute about whether such acceleration is occurring. But disputes are easily dismissed as the whining of denialists, so consider this. Between 1998 and about 2014 there was no statistically significant increase in global temperatures. Arguably there was even a slight cooling. That’s at least 16 years (some claim 18 years) in which the world’s hysteria grew exponentially, but there was no warming and, mysteriously, sea levels were rising even faster than usual.  How, exactly, does that work? Why would there be an acceleration in sea-level rise if such rises are directly linked to global warming?

“Oh,” you say, “the oceans are huge. There might be a lag – of decades – between atmospheric temperatures and sea-level rise.”

That sounds plausible. So this means that what was happening in global atmospheric temperatures in the 1970s, say, might take until 2000 to have an effect on sea levels. The trouble with this idea is that in the 1970s there was widespread media coverage, based on scientific agreement, that the Earth was cooling, and we should all prepare for the next ice age. But that sea-level graph just kept on tracking up then, and we haven’t noticed any lag effect of all that cooling at any stage later. In fact quite the reverse, if what you say is true.

“So what’s causing the sea level to rise, then?” you ask petulantly.

That’s a really, really good question, but because everybody thinks they know the answer nobody’s funding research to answer it. Imagine asking for $5 million for you and your team to work out why the sea level is rising.  You’d be laughed out of your job.

People mention thermal expansion and ice melt, and talk darkly about heat being stored somewhere in the ocean depths, like some communist plot. But just why sea levels have been marching up fairly consistently since the 19^th century, despite massive increases in atmospheric CO₂, and independently of whether global temperatures are warming, staying the same or cooling, is basically a mystery.

And please don’t say, “Oh, I’ll check all this on Wikipedia.” That source has become increasingly biased and unreliable, captured by powerful interests, especially in relation to climate change. Don’t take my word for it: listen to Larry Sanger, the cofounder of Wikipedia, who has forcefully argued the point on many occasions.

So, the take-home message: sea-level rise is very, very slow, and in some places in the world (where the land is rising) it may be non-existent, so check your local conditions. And sea-level rise is not obviously and directly related to rising temperatures and fossil fuel emissions, so don’t panic sell your beach house for a song and buy an electric car.

David Wolcott