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May 31, 2006

An Inconvenient Truth: Review

My friend Ryan's dad is a famous polar zoologist. Several years ago, I asked Ryan what his dad thought about "the whole global warming thing."

"Well, my dad's an optimist about global warming," Ryan said.

I breathed an inward sigh of relief.

"He's not nearly as dark as a lot of his colleagues."

I began to hope that the crisis had been exaggerated.

"My dad just thinks that global warming is going to kill off all the indigenous peoples and most of the wildlife in the arctic."

Last night I went to see Al Gore's new anti-global warming movie, An Inconvenient Truth (IMDB). I was very impressed. It's not great art, but it's terrific science. More importantly, it's an easily accessible message that everyone needs to hear. Go see it whether you feel like it or not and take your kids.

Al Gore lays out the evidence of an impending climate crisis clearly, rigorously, and compellingly. Given the profound implications Gore's argument, it seems almost perverse to dwell on the movie's aesthetics or its implications for American presidential politics. An Inconvenient Truth deserves to be assessed as a scientific, political, and moral argument for American leadership in the fight against global warming.

An Inconvenient Truth is the film version of Al Gore's famous global warming lecture, a free multi-media presentation he has delivered to thousands of people in dozens of cities around the world. Lecture footage and graphics are interspersed with biographical vignettes about Gore and staged footage of life on the anti-global warming sawdust trail.

Gore explains global warming terms that anyone can understand: Burning releases carbon, and carbon gets trapped in the atmosphere. Sunlight comes through the atmosphere and warms the earth, but carbon traps the heat, so temperatures rise. This phenomenon has been described as the greenhouse effect because carbon acts like the glass in a greenhouse. Sunlight goes in and turns to heat, but the heat can't escape because the glass insulates the greenhouse.

The caged heat is warming up the oceans. Icebergs shrink, glaciers retreat, and polar ice melts. Currently, giant ice masses like Greenland serve as giant mirrors that deflect sunlight back into space. However, as the surrounding water heats up, that ice begins to melt. More melting means less surface area for deflection. Less deflection means more heat absorption by the surrounding water, which in turn accelerates melting.

I didn't know this until the day before I saw the movie, but Ryan's dad gave Gore some of his slides on the melting ice in Greenland. Our fellow movie-goers probably thought it was a little weird when we started applauding for Dr. McCarthy's credit.

One of the best scenes in the movie is when Gore describes his trip under the North Pole on a nuclear sub. Submarine crews have been meticulously monitoring the thickness of the ice for decades because subs can only surface through relatively thin ice. Previously, these measurements were classified. Gore explains how he went up north to convince authorities to release this important data. The submariners' graph is now part of Gore's slide deck. It's just one of the innumerable pieces of converging evidence that the earth is warming up all over, especially at the poles.

A large percentage of the world's fresh water is locked away in ice. Millions of people get their drinking water from the runoff of glaciers, but glaciers are shrinking all over the world. Gore shows a long series of dramatic "before" and "after" shots of shrinking glaciers from Mount Kilimanjaro, to Patagonia, to Glacier National Park. (Links for illustration, not shots from the film.) If glacial melting continues, millions of people could face water shortages.

Furthermore, warming causes both floods and droughts. Hotter weather increases evaporation from the soil, exacerbating droughts and dustbowls. Rising temperatures also give rise to more violent storms by increasing evaporation from the seas. Storms also get stronger when they travel over warmer water. See RealClimate for a sober look at Katrina, global warming, and loaded dice.

Even more seriously, rising temperatures threaten ice reserves in the arctic and the antarctic. One of the most alarming signs of global warming the unprecedented ice breakup on the Antarctic Peninsula:

Antarctic Peninsula - Collapsing ice-shelf, January-February 2002. The northern section of the Larsen B ice shelf, an area of 1,250 square miles (3,250 km2), disintegrated in a period of 35 days. This was the largest collapse event of the last 30 years, bringing the total loss of ice extent from seven ice shelves to 6,760 square miles (17,500 km2) since 1974. The ice retreat is attributed to the regions strong warming trend - 4.5F (2.5C) in the last 50 years. [Climate Hot Map]

Gore explains that Antarctica has both land-based ice and sea-based ice. The floating ice is melting much faster than scientists expected it to. The rapid depletion of sea-based ice is exposing land-based ice to warmer temperatures. So, land-based ice is now melting much faster than expected.

The recent surge in land-based ice melting is alarming because of the implications for global sea levels. Land-based ice is ice propped up above sea level. If it melts, the runoff increases sea levels. (An floating iceberg that melts in the sea won't raise sea levels for the same reason that an ice cube floating in a drink won't overflow the glass when it melts.)

If a big chunk of land ice were to melt, world sea levels could rise by up to 20 feet. Gore shows a simulation of what a 20-foot rise in sea level would do to coastal cities around the world. One animation superimposed the effects of this 20-foot jump on a map of Manhattan, including the WTC memorial. It was eerie to sit in a Lower East Side theater straining to pick out the building I was sitting in on the satellite image before it disappeared under the advancing blue front.

One thing Gore doesn't explain clearly enough is how long it would take for world sea levels to rise by 20 feet if a major melting crisis happened. A year? Two years? A few months? The animation doesn't specify the timeframe. The take home message is not that people will drown en-masse as they did in New Orleans, but rather a large percentage of the world's coastal cities would have to be abandoned.

Melting ice also dilutes the sea. Salinity is integral to the ocean current systems regulate the global climate. The gulfstream is part of a so-called conveyer belt that carriers warm water from the Southern hemisphere northwards. The warm surface currents modulate the climates of the land masses they pass. These warm currents provide Europe with one third as much warmth as direct sunlight. Surface currents also become saltier as they travel because of evaporation. Eventually, this water gets cold enough and salty enough to sink to the bottom and resume the cycle.

If Greenland were to melt rapidly, massive amounts of fresh water could be released into the sea. If the salt levels dropped too much, the conveyer belt could stop working because the warmer water wouldn't sink back down again. Geologists say that the last time this system broke down, Europe was enveloped by an ice age in as little as a decade.

Real Climate's review of An Inconvenient Truth gives the production high marks for scientific accuracy. However, the review's author notes that projecting future temperatures based on the past correlations between carbon dioxide and the projected carbon levels may overestimate the expected rise in temperature. The reviewer doesn't doubt that temperatures will rise because of CO2, he just thinks that they may not rise quite as much you might think based on past correlations between CO2 and temperature because other cooling trends may offset the effects of CO2. If I remember correctly, Gore doesn't actually project the temperature forward. He superimposes the graphs of global temperature and global carbon levels. The carbon line gets projected into the future, but the temperature line stops at the present. Gore invites the viewer to look at the block-long pattern of correlations and infer what the temperature will do as carbon emissions rise exponentially.

The central plank of global warming denial is that that correlation isn't causation. Even skeptics can't deny the basic greenhouse mechanism. Nor can they deny that global temperature has been closely correlated with carbon dioxide levels for tens of thousands of years. There's no getting around the fact that human beings are adding vastly more carbon to the earth's atmosphere than it has ever contained. The two major culprits are fossil fuels and burning tropical forests. Increasing industrialization and population growth can be expected to accelerate carbon emission trends. Tellingly, the earth's temperature has been rising more or less proportionately to the increases in atmospheric carbon since the industrial revolution.

Still, we can't do controlled experiments with the world's climate. Any evidence that increased carbon levels cause increased temperatures in the real world is going to be correlational. Any evidence about the likely mechanisms of global warming that is based on models or laboratory experiments can be dismissed as being unrealistically simplistic. (Of course, the hired shills will also dismiss as mere correlation the fact that their denials are highly correlated with their pay checks from the oil and gas lobby.) This self-sealing rhetoric of denial more or less guarantees that we will be submerged without knowing that global warming is real.

We can only hope that movies like An Inconvenient Truth can cut through the haze of disinformation and denial.


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» Optimism from Political Animal
OPTIMISM....Lindsay Beyerstein passes along the following anecdote about what the word optimist means when the subject is global warming:My friend Ryan's dad is a famous polar zoologist. Several years ago, I asked Ryan what his dad thought about "the w... [Read More]

» Optimism from Political Animal
OPTIMISM....Lindsay Beyerstein passes along the following anecdote about what the word optimist means when the subject is global warming:My friend Ryan's dad is a famous polar zoologist. Several years ago, I asked Ryan what his dad thought about "the w... [Read More]

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Every now and then the world is trying to tell you something, and events conspire in a flash of synchronicity to reveal a truth so deep and powerful that ordinary genius alone would have been insufficient to figure it out. Such was the case recently,... [Read More]



You missed my point, which had not one thing to do with the number of storms, and I am well aware of hurricane cycles. It is the strength of the storms, the speed with which they gained that strength, how much it exceeded predictions, and the clustering of three such anomalously powerful storms in a single year. It would take a very large number of storms to make that record-breaking cluster be "not a surprise". It would be interesting to know how deep the hurricane churn actually is, and how water temperatures are changing at that depth. Direct observations of water movement in a category 3+ storm are life- and equipment-threatening, so I'm not too surprised if we don't have this data yet.

"We do not have accurate or detailed storm information for the past one hundred years for starters,"

We might. Chemical analysis of tree rings could reveal increased levels of elements found in seawater. This would be evidence of storm surges. It would be one possible method. It would require a very methodical and wide ranging survey though. I think I'll poke around on web-of-science for something like it.

Although, what I recall hearing was not that the hurricane cycle is hundreds of years, but that it is ~30 years, and has been going on for hundreds of years. Even so, last years storms were worse than those of 30 or 60 years ago.

"Do you judge science by it's conclusions, or by the methods used to reach conclusions?

Gore perfectly illustrates the old adage that a little knowledge is a dangerous thing."

There's another old adage that goes like this, "When critquing the work of scientists it is often best to be specific in your criticism." Which methods are you dubious about?

helium3 - it's best to read what you think you're responding to. (i.e., did I say something about doubting methods?)

But since you bring it up, I mm dubious about the reliability of long-range predictions based on simulations of complex, semi-chaotic systems. And lest I be misunderstood... I think there are all sorts of good reasons to get off the hydrocarbon bandwagon that don't require me to adopt an uncritical attitude.

Why is it that GW skeptics who mention "complex, semi-chaotic systems" always tend to assume that the unpredictability of these systems will count in the direction of less, rather than more catastrophe? If we can't exactly predict what will happen, isn't it just as likely that it might be worse than what Gore and others are suggesting?

Also, GW skeptics can find problems with some individual pieces of the evidence for GW, but there is plenty more evidence that they don't touch. The strength of the scientific case is in the agreement between many kinds of evidence, all pointing in the same direction, It seems to me.

JonJ -
It's inaccurate to call me a GW skeptic since I'm not at all skeptical about the reality of global warming. What I'm skeptical about is the adequacy of the explanations being offered for observed warming and the long-range predictions of catastrophic consequences. Nor do I assume that the unpredictability of complex, semi-chaotic systems "will count in the direction of less, rather than more catastrophe." What I do assume is that a critical attitude is desirable.

I agree, as there are on going limnology studies occurring in my state to study historic weather patterns to determine historic MFL's and set current values on the fresh water systems. Don't forget ice core data, also an ongoing historic indicator source:

But the level of detail I am talking about is the exact number of storms, point of generation, what the current upper level and other surrounding weather conditions were , what direction they moved, where they made land fall, what was the barometric pressures and top wind speeds...etc.. These are the kind of details I am speaking of. For that degree of in depth data we have maybe 30- 40 years worth, with some fragments of data into the early part of the last century and latter part of the 19th century.

So when people start predicting storm counts and intensity, it is from long term broad spectrum data or a very shot term specific source, both sources lacking what the other possesses.

Not to make light of a very serious crisis, but this story started me off with a chuckle: where else but Majikthise would you ever see the phrase "famous polar zoologist"? ;-)

Don't forget the methane green house effect is much more than CO2 and man made sorces are pretty big contributors 1.5 billion cows worldwide compared to natures top population of American bison 30 to 60 million
luckily we can control even the emmisions of our livestock

here is a different look that says natural sorces dwarf manmade sorces of greenhouse gasses including water vapor.

PS. If NOAA scientists want to make an accurate>graph they should not start a graph Y axis that far up the scale above zero and should show larger areas of data like the CO2 data from arctic cores that show we are actually in a mild climate zone compared to other times in history. Some good arguments are made that Water vapor (which is almost all natural) percentages compared to natural and manmade levels of CO2 and other gasses make our contribution look small and we are really just contributing to>Junkscience

I'm not convinced. This is more of a one sided arguement with the omission of many dissenting facts. If I would have done research like this in grad school my professors would have thrown me out on my ear. The CO2 level argument is weak. The percent of green house gasses that can be attributed to human activity (anthropogenic) is VASTLY over stated in this presentation. If water vapor is considered (which it must as it is the most significant contributor to GHG) then man at best can only be 'blamed' for less than 1% of the problem. The statements made in Inconvenient Truth are disingenuous at best if not blatant fraud. Global warming is a fact but its cause is not man made nor can it be resolved by man. I'm all for taking care of our environment but to use false scare tactics is dishonest. The cause of global warming is not clear but I would put my money on the documented increase in solar activity before I would blame man. Folks this planet is extremely resilient and human kind is no more than a pimple on mother earth's butt. Get over it.

Great review .. Mr. Gore's movie somehow made it to my little corner of the world, and I was surprised by how entertaining it was, along with being very informative and frightening

I totally agree that this is a must-see movie. I think it's one of the best pieces of environmental propaganda I've ever seen. It's very well researched and well presented.

The problem with "An Inconvenient Truth" is that it is not backed up by the scientific literature. The break up of the Antarctic ice sheet you mention has been more than compensated by increases in the depth of the ice in the center of the Antarctic Continent. Also the consensus is that if nothing is done to curb CO2 increases it will take 1000 years, not 100 for the Greenland Ice Shelf to melt. Expected Sea level increases by 2100 are 8" to 17" not the 20 FEET Al Gore claims. The movie is pure propaganda and as such is a work of fiction.

Posted by: bob koepp | June 02, 2006 at 12:11 PM

"Why is it that GW skeptics who mention "complex, semi-chaotic systems" always tend to assume that the unpredictability of these systems will count in the direction of less, rather than more catastrophe? If we can't exactly predict what will happen, isn't it just as likely that it might be worse than what Gore and others are suggesting?"

Your statement is true only if Gore was presenting a middle of the road view. Actually he is presenting the most extreme and pessimistic view. The chances of it being correct are slim indeed.

I thought that "An Inconvenient Truth" was a great movie and it really helped me realize how much global warming will effect the earth and how it will change our lives forever. Thanks for writing the article!!

You mention that in the graph scene, Al Gore projects the carbon line into the future, but stops the temperature line in the present. I think he stopped both lines back a few years though, like 2000 or something. Then he showed the carbon line where it is today (which was higher than any time in the past 650,000 years), but he didn't show the temperature line where it is today. Then he proceeded to show the projected CO2 line, which went off the screen.

My question is that if the CO2 line is already much higher today than it has been at any point in the past, why hasn't the temperature line gone up just as much? He didn't even show the temperature line where it was today, and I suspect it is because it doesn't track with the CO2 line recently.

Al Gore says that a small movement in the temperature line was the difference between today's temperatures and an ice age. So if the temperature line went up as much as the CO2 line has already, we'd be burning up! But currently, at most, there has been a moderate warming--nothing as drastic as the difference between our comfortable temperatures today and ice age temperatures.

So I'm not convinced that CO2 levels directly cause a rise in temperatures. I've actually been reading that it's the other way around. Higher temperatures cause higher CO2 levels because warmer oceans don't absorb as much of the gases in our atmosphere and actually cause a release of gases, called "outgassing". There also is a gap of 800 years between a rise in temperatures then a rise in the CO2. The rise and fall on the historic graph has all been from nature and the sun. But CO2 levels have risen so much more than in the past because of the industrial revolution. But it is not causing a drastic increase in temperatures since the atmosphere can only hold so much CO2. I've read that we have currently heated up 50-70% of what we can possibly heat up because of the limited saturation level.

Sorry so long, but this is all I've been reading about. It's hard to really know the truth, probably because scientists themselves can't agree on what is correct.

So if the temperature line went up as much as the CO2 line has already, we'd be burning up!

That's not entirely accurate. The most important characteristic of glacial periods isn't low overall temperature, but low temperature on land in the summer. The mechanisms that have controlled glaciations over the last few million years are based on temperature gradient in the northern hemisphere; when it is too low, glaciers fail to melt in the spring, triggering a runaway cooling effect that lasts until the temperature gradient becomes high enough.

On another note, it's hard to say how much CO2 can theoretically warm the atmosphere. But in the Cryogenian, one theory is that the Earth wasn't continuously frozen over, but rather had periods in which it was ice-free. Whenever the Earth was frozen over there would be no water vapor in the sky to wash out CO2 from outgassing, so CO2 could build up until it would trigger a global warming effect that could melt all the ice within a millennium or even a century. That would inject water vapor into the atmosphere that would wash out the CO2, reducing temperatures until the planet froze over again, lather, rinse, repeat.

There also is a gap of 800 years between a rise in temperatures then a rise in the CO2.

Maybe... maybe not. It's not clear that the Medieval Warm Period and the Little Ice Age were global rather than European phenomena.

But it is not causing a drastic increase in temperatures since the atmosphere can only hold so much CO2.

In past eras, CO2 levels were orders of magnitude higher than today. When you look at scales of millions of years, CO2 levels today are the lowest ever. It's just that solar output is also at its highest, and at any rate New York and Los Angeles and Shanghai and Dhaka are built based on sea levels today, not based on sea levels as they would be if CO2 concentration was at Cambrian levels.

As I understand it, tree rings, Greenland ice cores, ocean sediments and all sorts of other evidence suggests that the earth has gone through dozens of warming and cooling periods over the last 300,000 years. Since man wasn't around to burn fossil fuels to create C02 to cause all those warming periods, what did cause them? "An Inconvenient Truth" doesn't say. I'be heard people say that the earth is hotter now than it has been at any time in the last 1000 years. I have seen temperature graphs that show the earth was actually hotter in the Medieval Climate Optimum (900 to 1300 AD). In contrast, the 300 years just before that (600 to 900 AD) was a cooling period. Civilization retreated into the Dark Ages. Millions were starving. People were smaller from lack of food. So many people today act as if (gently) rising temperatures are going to wipe out the planet. Throughout history most people preferred warmer times over cooler ones. Warmer climates meant more stable weather, more rain, vegetation flourished. Populations grew. Mankind has been through warm periods and cold periods many times. And the warm times have always been better.


Go back to cosmicvariance.

Yeah, you "Lisa", "Gene".

I see 'The great Global Warming Swindle' has made its impact. Pity that what wasn't a lie in that movie was a mischaracterization.
'Warmer times were always better times' - depends how warm and when - warmer times in the American Southwest were times of mass famine and populations vanishing (study the Anasazi).
If you'd like to review a summary of why scientists are concerned, perhaps you can check out (and look at 'How to Talk to a Climate Skeptic')
and for a scientific fisking of 'The Great Global Warming Swindle', you can check out Climate of Denial's pages, at

Sorry, Gene.

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