Guest Post by Bob Tisdale
Yale University’s Katherine Bagley interviewed James Hansen, former director of NASA’s Goddard Institute for Space Studies, in the post For James Hansen, the Science Demands Activism on Climate at YaleEnvironment360. That interview was replayed in the article Climate scientist James Hansen ‘I don’t think I’m an alarmist’ at The Guardian.
In that interview, Hansen admitted a couple of basic things that many people do not realize. So if you’re new to discussions of global warming and rising sea levels read on.
First, global surface temperatures were warmer during the last interglacial than they are today. An interglacial is a period between ice ages. That will be news to many readers.
How then, many will wonder, do we know for sure that the recent warming was caused by manmade greenhouse gases since we’re still within the realm of natural variability?
Of course the answer is: Climate models tell us so, even though those climate models are not simulating Earth’s climate as it existed in the past, as it exists now, and as it might exist in the future…climate models do not simulate naturally occurring ocean-atmosphere processes that can cause global warming.
Hansen’s second admission was sea levels were 6 to 9 meters (20 to 30 feet) higher during the last interglacial than they are today. Here’s an illustration from my ebook On Global Warming and the Illusion of Control – Part 1 (700+ page, 25MB .pdf).
But what Hansen failed to say is that paleoclimatological studies have indicated that it took a number of millennia for sea levels to rise those 6 to 9 meters when temperatures were warmer than today. See:
- Kopp et al. (2013) Probabilistic assessment of sea level variations during the last interglacial stage, and
- Dutton & Lambeck (2012) Ice volume and sea level during the last interglacial.
The corresponding portion of the Hansen interview (my boldface and brackets):
James Hansen: We know from the earth’s history that 2 degrees would eventually lead to sea level rise of several meters. The last inner glacial [sic] period, [that should read interglacial period] 120,000 years ago, that’s the last time it was warmer than today, sea level was 6 to 9 meters higher — that would mean loss of almost all coastal cities. It’s unthinkable that we walk into such a situation with our eyes open, and yet, the science is very well understood.
There’s no argument about the fact that we will lose the coastal areas, now occupied by most of the large cities of the world. It’s only a question of how soon. That message, I don’t think, has been clearly brought to the policymakers and the public…
If I was new to the discussions of global warming and sea level rise, that would be as far as I would have needed to read the interview. He would have turned me into a skeptic right there.
But contrary to his claims about alarmism, Hansen then goes on to play alarmist and discuss how his recent modeling efforts and resulting paper indicate that the rise maybe-sorta-could occur abruptly.
… More than 190 nations agreed [at the Paris climate conference last December] that we should avoid dangerous human-made climate change. That loss of coastal cities would be a dangerous outcome. It’s hard to imagine that the world will be governable if this happened relatively rapidly. What we conclude is that the timescale for ice-sheet disintegration is probably a lot shorter than has been assumed in the intergovernmental discussions.
Of course, even proponents of the hypothesis of human-induced global warming found the recent Hansen et al. (2016) study (Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous) to be nonsense. Even the title of the paper includes the oft-used weasel words “could be”. See the following posts at WattsUpWithThat:
- James Hansen’s latest doomsday paper falls flat on its face, grounds his ‘flying boulders’
- Schism on the Left: James Hansen’s climatic ‘canon’ gets fired from a cannon
Two quotes from my ebook On Global Warming and the Illusion of Control – Part 1.
From the Closing to Chapter 1.16 – Sea Levels Are Rising:
This chapter opened: For many people, especially for persons living near the coasts, sea level is the critical metric associated with global warming and climate change.
Sea levels have risen since the peak of the last ice age, and, if history repeats itself, they will continue to rise to the heights achieved during the last interglacial: 5 to 10 meters (16 to 32 feet) higher.
But as discussed in this chapter, there are a multitude of factors that can contribute to the rise, or fall, in local sea level. Rising sea levels are, therefore, a local concern, as are steps to combat it, as I’ve noted numerous times in this chapter. Many countries and communities are already implementing measures to reduce the impacts of rising sea levels—employing methods designed specifically for their location.
Assuming that man-made greenhouse gases have contributed to the rate at which global sea levels are rising, curtailing man-made greenhouse gas emissions would only slow the rate, not stop it. Then again, The Houston & Dean (2010) Sea-Level Acceleration Based on U.S. Tide Gauges and Extensions of Previous Global-Gauge Analyses found that the rise in sea levels had not accelerated with global warming.
And from the Introduction, I began the discussion under the heading of SEA LEVELS, ON THE OTHER HAND, PRESENT AN ENTIRELY DIFFERENT PROBLEM:
Again, even if we could turn back CO2 levels to preindustrial values, sea levels would continue to rise. Sea levels have been rising since the end of the last ice age, and they will continue to do so until Earth cools once again and we head toward another ice age. That is, the only way to stop sea levels from rising is to start accumulating water on land in the form of ice.
Further, the rate at which global sea levels might possibly change in the future, in response to the hypothetical effects of man-made greenhouse gases, is still the subject of wide ranges of uncertainty and open debate…and the subject of even more alarmism from activists and the media, if that’s possible.
And I closed the discussion under that heading with:
The ridiculous suggestions by politicians and alarmists that we can control rising sea levels by reducing greenhouse gas emissions is one of the primary reasons for the title of this book: On Global Warming and the Illusion of Control.
UPDATE: I corrected a typo in the opening sentence.