Al Gore’s movie ‘An Inconvenient Truth’ says sea levels could rise up to 20 feet. Is this true?

Asks Steve from Florida

December 1, 2008
The Maldives, a group of Indian Ocean islands, could be threatened by even a meter rise in sea level. <br>[Credit: Nattu, flickr.com]
The Maldives, a group of Indian Ocean islands, could be threatened by even a meter rise in sea level.
[Credit: Nattu, flickr.com]

Some of the most memorable images from Al Gore’s movie, An Inconvenient Truth, are the graphics that show how rising ocean levels will dramatically alter our planet’s coastlines. As Greenland’s ice sheets collapse, Gore predicts that our shores will be flooded and sea-bordering cities will sink beneath the water leaving millions of people homeless. His narration tells the audience that, due to global warming, melting ice could release enough water to cause at 20-foot rise in sea level “in the near future.”

Although he doesn’t give a clear time frame for the 20-foot sea level rise, Gore’s statement seems to contradict several recent reports, including one published in 2008, that predict much smaller rises during this century.

Scientists say that the two main causes of rising sea levels are water expanding as it warms, known as thermal expansion, and melting land-based ice, such as ice from Antarctica and Greenland.

In 2007, the International Panel on Climate Change, an organization composed of scientists and policy makers around the world who monitor human-caused climate change, estimated that sea levels would rise 0.18 to 0.6 meters (0.59 to 2.0 feet) over the next 100 years. The IPCC based this prediction primarily on how much the ocean waters are expected to warm and expand.

The panel also factored in the ice melting from Greenland and Antarctica based on how much these bodies have melted in recent years—from 1993 to 2003. But the estimates do not account for any changes in the speed of the weakened ice that flows from the glaciers into the ocean—either from melting ice or iceberg break-off, which may happen in the future. The IPCC acknowledged the limitations of their projections and said that sea level rise could be higher if the ice sheets break down more rapidly.

The IPCC did not include changes in ice flow because these types of changes are not very well understood. However, a study published this year in the journal Science attempts to set an upper limit on sea level rise by 2100.

“We have estimated limits on sea level rise during the next century by considering simple constraints on glacier and ice sheet motion,” says Joel Harper, an author of this study and a glacier expert at the University of Montana in Missoula. “Our work suggests that a 0.8-meter [2.6 feet] sea level rise is plausible, two-meter [6.5 feet] is only possible under extreme conditions, and more than two-meter is unlikely,” he says.

To make their calculations, the researchers took into account the rate of ice flow from Greenland, Antarctica, and glaciers and ice caps from other parts of the world. They took current values of glacial ice-flow speeds and adjusted the values based on changes that they think could reasonably occur in the future, such as accelerated ice flow from certain glaciers. They then used these modified values to come up with low, medium and high estimates of future sea-level rise.

The researchers also determined that Greenland’s glaciers—specifically, the ones with outlets under water—would have to move about 40 times faster than they do now to achieve a rise of two meters over the next 100 years. And this increased ice-flow speed would need to start immediately and continue for the rest of the 21st century.

“Even by assuming vastly accelerated rates of discharge, the glaciers can’t surge fast enough to meet the required sea-level rise targets [of two to five meters] within a hundred years,” says Vivien Gornitz, a geologist at Columbia University, who was not involved in this study.

While this new sea-level rise estimate is much lower than Gore’s 20-foot prediction, it is still significant.

“An enormous number of people live within one meter of sea level. It is something like 145 million people,” says glacier expert Harper. “Most of these are in third world Asia where they have few resources to adapt to change. Even in the US, the costs will be enormous,” he adds.

The researchers think that knowing how high sea levels may rise will let countries gauge how much they need to spend on new infrastructure, such as levees, to prepare for changes to their coastlines.

Harper hopes that further research will lead to more precise estimates. “Learning more about the physics which govern glacier dynamics will be a big step,” he says.

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About the Author



Paul says:

Some other research to ponder:

Response of the global ocean to Greenland and Antarctic ice melting –
D. Stammer, Institut für Meereskunde, Universität Hamburg, Hamburg, Germany

Millennial Atmospheric Lifetime of Fossil Fuel CO2, D. Archer and V. Brovkin, Climatic Change 90:283-297, 2008.

D.Stammers study looks at the flow of water around the world and points out that it takes a number of decades for water deposited in the Atlantic to distribute around the worlds oceans. eg. the Atlantic may ‘bulge’ initially so that sea levels are higher at Atlantic coasts.

I’m not sure how much this applies to current rates of break up, melting.

But even if it takes one thousand years to reach 20 ft, does the time scale matter?
As D. Archer (Chicago Uni) points out, a proportion of CO2 we emit today will remain in the atmosphere for thousands of years (if we don’t do anything to draw it down). So maybe Gore got the time scales wrong (or not so wrong?) but if we carry on as we are, massive sea level rises are inevitable.

terry says:

To the young people out there, every so many years we must face another claimed historic calamity for our planet. Al Gore is adding his alrmist hysteria. His outlandish projections are not supported by the scientific community. If he didn’t have the nerve to claim a 20ft water level increase no one would listen. In recent history claims of a 1 degree rise and drop in earth temp have caused mini hysteria.I guess that means that we are at the optimum temp today. What drivel!

Alexis says:

I don’t really care if Al Gore was off on his calculations. What he’s trying to do is try to make people feel the need to help the earth. If fear is the only way to get people to start helping, I say go for it! People don’t seem to notice the severity of things until something big happens, and, by then, it’s usually too late.

Jeff says:

So, I have been studying the reported temperatures in Connecticut, USA for the past year and guess what? Average temp is down! OK, one years’ worth of data isn’t enough….but what is? The projections used in “An Inconvenient truth” come from models, which have not been tested. In fact, the models cannot predict weather or temperatures in any particular geographic region, they only predict averages for the entire world. The predictions are wrong. They’re better than they were, but they are still off by a great extent.
My answer: keep observing the world around us; report the facts as observed; take action when necessary; keep your money in your pcket until it is time to do something.

Stuey says:

“The researchers think that knowing how high sea levels may rise will let countries gauge how much they need to spend on new infrastructure, such as levees, to prepare for changes to their coastlines.” The construction of levies would simply add more CO2 to the environment as would the building of new housing. The people who are below sea level will have to move but to where?
Too much time is spent on nitpicking the scientific results. The heat is rising, the poles & glaciers are melting, and if anything the conservative scientific community has under estimated both the rapidity of the enormity of the changes. Our species does not have the smarts to deal with this problem.

Tony says:

Al Gore is a liar. His Church of Climatology brooks no oppossition.Al gore is not about “helping the earth” but about lining his own pockets with his phoney envoirnmentalism. Lord Momckton a British Climatologist and A British hight court Judge have both refuted his lies. His propagandistic film an “Inconvenient Truth, Should be renamed “An Opportunistic Lie” The Un Climate panel has falisfied data and told outright lies to prove the political point of that there is man made global warming. Former Un climate panel scientists have resigned from the oanel in protest at this and the fact that their reports are being edited by civil servants. Manmade made global warming is a scam, a political underpinned by junk science.

Whatever stuey says:

@ Stuey: “The people who are below sea level will have to move but to where?”
Well Stuey, thanks to global warming, land that was once covered by glaciers will now be inhabitable!

@ Alexis: If you are ok with the perpetuation of lies that is your prorogative but it is shameful to dupe the world so that you can get your way, isn’t that what Hitler did with what he viewed as a “problem.” Seriously, donate to Gore’s propaganda fund all you want but don’t justify the lies.

I am an environmentalist, always have been, and it’s been a struggle to show, teach, and convince people to live environmentally friendly and live sustainably and hacks like Gore are destroying all the work that has been done by perpetuation the lies. Gore is an opportunistic liar and because of Hollywood’s new pet project (jumping on Gore’s band wagon) the simple masses are forgetting what really matter to the environment and calling for taxing of industry and shuttting down the oil sands; the very sources that supplies our wasteful over consumerism. The real work needs to be done at the individual level. Copenhagen and Gore are destroying the environmental cause and feeding the fanatics.

Cole says:

Let’s not forget about the disappearance of the island of Atlantis and the Great Flood that Noah endured. We need to blame Global Warming for that too.

judgeroybean says:

Gore is fulla of it. If he believed this nonsense, explain why he bought luxury digs at sea level in Montecito, Ca., and San Frisco? Sorry, but you have to Google it yourself. Our server is owned by Gorebots so we cannot link to articles.

David Oldham says:

The 100th anniversary of the Panama Canal revealed a simple but important fact. ocean/sea level recorded on the gates at each end have not changed in 100 years. Junk science is only an attempt to lower the amount of money in your pocket by raising your emotional reaction to an obvious potential threat. Al Gore understood this business model concept only to well. The 100’s of millions made on his film will keep the lights on his mansion for the rest of his life and then some.

Josef Blough says:

People, the so called … climate change … is nothing more than diversion from the truth (that global warming is a farce) and people are still gullible enough to buy into it. Climate change? Please, how original. It’s called weather folks. Yes, I know, the definitions of climate and weather differ in the dictionary, but that doesn’t change the fact they are directly proportional with each other, in that weather, in so many words, is a daily account of climate.

Regardless, of course climate changes. It changes every day, every year, etc. Always has, always will. Why do you actually think they changed it from global warming to climate change? Because NO ONE can deny climate changes. Much like a fisherman who can’t get a fish to bite on his hook, but keeps changing bait until it does, so does the Algore crowd.

Should we be aware of our impact on the planet? Well of course, no one is denying that. However … one must understand it’s not so much what the supposed experts are telling us, it’s what they aren’t telling us, which can, and obviously has, painted a very colorful and inaccurate portrait of the subject as a whole, if not out and out lying about it. For instance, stating glacier ice at Antarctica is decreasing, but conveniently leave out the fact it’s because of a volcano, not mention it’s actually been increasing on the other side. In fact, Antarctica ice overall has been growing since 1979. They also claim global temps are going up when they have proof it’s been going down the past 15+yrs. And on and on and on. The truth is, global climate is ever changing from cycle to cycle and has since the dawn of time and its unlikely man has had much to do with it, if at all.

Considering the age of the Earth in relation to the fact we’ve only been doing serious studies of the atmosphere since the 1800’s, there is absolutely no way scientists of today could know with any certainty the accuracy and validity of their claims in such a relatively short period of time. Especially since much, if not most, is a product of computer models, equations and crumbs of questionable data from questionable so called scientists on government payrolls, instead of hundreds and thousands of years of real data. Remember, state of the art science for it’s time also claimed the Earth was flat and that man would never fly. And we all know how those turned out. In just a few years, the science of today will also be thought of as primitive and the cycle repeats itself all over again. Unproven science is only a theory, and so far, that’s all they have and flimsy ones at that. And even more so since in this case, it’s junk science with the end goal of global control. At the end of the day, there is absolutely NOTHING anyone can do or say to change that.

Martha says:

I watched Al Gore’s presentation last night, 10 years later, and many predictions are are coming true. The weather has changed significantly. We see evidence in the droughts and floods taking place. I’m not a scientist so I can’t provide a scientific explanation, I am a grandmother of a young child and I worry about her quality of life in the future. We need to stop criticising and start working together to improve our environment so our grand children and their grand children can live in a healthy world.

Dennis says:

I have not seen AL Gore’s movie but scientists agree that the sea was 20 feet higher than it is now during the last interglacial period. They also know that the sea level has risen almost 400 feet since the ice age ended about 12,000 years ago. Since the CO2 level is higher now than it was in the last interglacial, 20 feet of sea level rise seems to be inevitable. The only question is how long it will take. The chaos caused by coastal cities being flooded will certainly disrupt the civilization we enjoy today.

Pat Moseman says:

This hysteria is all about making money, control, shutting down naysayers, by not publishing their articles, ridiculing those who disagree and refusing research grants to disbelievers. I have lived in Florida for 45 years and the same rocks along the shore are still there! Why did the glaciers melt the last time, thousands of years before?

Stuart Mathieson says:

No climate scientist denied climate has natural cycles and always has long before we appeared on the scene. But that does not mean our activities (burning fossil fuels and forests) isn’t having an increasingly significant impact. We are releasing the stored energy of millions of years if sunlight into our atmosphere. That’s what coal and oil is. Fossilised sunlight.

Adrian D Reif says:

The Maldives and other atolls around the world are not disappearing due to sea level rise. Ask any geologist how atolls are formed and why the are subsiding.

James says:

I pray that we turn things around, so that we all can see how badly these comments have aged.
We each have an opportunity, today, to look inward for the values we hold most dear – and to be sure that the choices we make are truly in support of those values, rather than shield ourselves from truths that are painful and inconvenient.

Suh Dude says:

Imagine being James and thinking the comments aged badly in his favor…..

Jimmy Johnston says:

Yes, it has been 14 years since the first post and what have Climate believers done to help the planet in that time. Ask for money, complain, take your money through taxes, complain, etc. The inconvenient truth I see today is a lot more trash littering the sides of our highways. many more homeless in communities, and regulations against farmers that will contribute to famine around the globe. Republicans have offered suggestions such as nuclear energy and desalination plants, but Democrats refuse to compromise. So, what exactly is the priority? Saving the planet or taking our money?

Iggy Zans says:

Its OZONE people!

Bill says:

We’re not dead yet.

Craig Verdi says:

The droughts and floods we “see” are not there. The IPCC report of 2023 says that coastal erosion and river flooding have not started happening yet. It is almost impossible to find that part of the report. Go to Roger Pielke’s Substack to see the parts of the report that we are not yet (probably won’t in my mind) There is also not increased fire weather. I have it on my Substack article at

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