# climate change in our lifetime **URL:** \ **Category:** Great Debates\ **Created:** [December 27, 2006, 2:25pm UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737 "2006-12-27T14:25:43Z")\ **Posts on this page:** 20\ **Page:** 4
**Author:** ![ITR\_champion](https://avatars.discourse-cdn.com/v4/letter/i/c67d28/32.png) [@ITR\_champion](https://boards.straightdope.com/u/ITR_champion)\ **Post date:** [December 29, 2006, 6:43pm UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/61 "2006-12-29T18:43:00Z")
Traditionally sea levels are measured relative to benchmarks on nearby landmasses. Now we also have several satellites capable of mapping sea levels, and those obviously don’t depend on the landmasses remaining fixed. [See here](http://sealevel.colorado.edu/) for in-depth discussion and a graph of global average sea level over the past twelve years. Feel free to compare that graph with Michael Crichton’s claim that there’s “no clear trend” in sea level data. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [December 29, 2006, 9:39pm UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/62 "2006-12-29T21:39:10Z")
[QUOTE=ITR champion] Furthermore, it should be noted that coral reefs aren’t vanishing solely due to physical destruction. [They’re also being damaged](http://www.time.com/time/magazine/article/0,9171,1050329-5,00.html) by rising sea temperatures, a.k.a. global warming. [/QUOTE] Furthermore, independent of climate change, the addition of CO2 to the atmosphere is [causing the upper levels of the ocean to become more acidic](http://www.royalsoc.ac.uk/document.asp?id=3249) as some of the excess CO2 gets absorbed there. And, this is also a concern in regards to the coral reefs. ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [December 29, 2006, 10:23pm UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/63 "2006-12-29T22:23:35Z")
> [@SenitentMeat](#): > > …(And what the fuck has Mars got to do with anything? I know ACC deniers are on another planet, but would have thought Venus was more appropriate to the “debate”, such as it is.) Those six dots _preceding_ the quote speak volumes, **Leaffan**. ---
**Author:** ![Least\_Original\_User\_Name\_Ever](https://avatars.discourse-cdn.com/v4/letter/l/e480ec/32.png) [@Least\_Original\_User\_Name\_Ever](https://boards.straightdope.com/u/Least_Original_User_Name_Ever)\ **Post date:** [December 29, 2006, 10:45pm UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/64 "2006-12-29T22:45:24Z")
[QUOTE=ralph124c] Geologists tell us that New England is rising at about 2-3" per century (the land is rebounding from being compressed by the ice cap that covered NE some 25,000 years ago). The island of Trinidad appears to be sinking: but geologists aren’t sure if this is due to the ocean level rising, or the land subsiding (the theory is that the sedimants of the Orinoco delta are compressing the seabed). Greenland will begin rising, as its ice cap melts off-the immense weight of the icecap (over a mile thick) has dpressed the island. So, how are we sure what is going on? I think you can find land rising and subsiing-it is not clear which effect is the dominant one. [/QUOTE] This is a very interesting point, and I’d like to see it addressed properly. ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [December 30, 2006, 12:49am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/65 "2006-12-30T00:49:50Z")
[QUOTE=Least Original User Name Ever] This is a very interesting point, and I’d like to see it addressed properly. [/QUOTE] What is 1 cm per century compared to a possible [30](http://news.bbc.co.uk/1/hi/sci/tech/4651876.stm)? ---
**Author:** ![Baldwin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/baldwin/32/7264_2.png) [@Baldwin](https://boards.straightdope.com/u/Baldwin)\ **Post date:** [December 30, 2006, 1:51am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/66 "2006-12-30T01:51:35Z")
> [@BrainGlutton](#): > > When floating ice melts it does not change the sea level (but see Greenland and Antarctica). But an increase in the world ocean’s average temperature will change the sea level. A mass of warm water occupies more volume than an equivalent mass of cool water. Again, the melting of floating ice fields does in fact raise sea level a bit, because of the difference in salinity between the seawater and the ice. It honestly baffles me how a subject like this gets treated as if it were a political issue, not a question of science. Sometimes I hear folks who really talk as if they’ve got a backup planet to live on in case we screw up this one. (We’re not in danger of screwing up the whole planet, of course – just the thin film on the surface that constitutes our **entire** habitable environment.) ---
**Author:** ![Bushfan](https://avatars.discourse-cdn.com/v4/letter/b/f19dbf/32.png) [@Bushfan](https://boards.straightdope.com/u/Bushfan)\ **Post date:** [December 30, 2006, 1:52am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/67 "2006-12-30T01:52:20Z")
After reading this thread, I decided to rent ‘An Inconvenient Truth’. Obviously aimed at a less sophisticated audience i.e., _Joe Shmoe_, it appeared to me that the piece sought to correlate an oodle of yet uncorrelated data. I was moved, but aren’t many of the points made in the film what > [@](#): > > could be expected as we are now on the downslope of a previous ice age? Also, I Believe that the CO2 measurements that were being taken (cited) were from the central Pacific while the levels being cited were based on cores taken from the poles. Could there be a possible discrepency between these numbers that could effect the overall results? I’m pleading ignorance, so don’t beat me up! ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [December 30, 2006, 3:33am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/68 "2006-12-30T03:33:20Z")
[QUOTE=Bushfan] I was moved, but aren’t many of the points made in the film what be expected as we are now on the downslope of a previous ice age? [/quote] Not sure what you are referring to exactly here. We are in an interglacial period between ice ages and have been for the last 10,000 years or so…but temperatures are not still rising from that. In fact, there had already been some modest amount of cooling from the warmth of several thousand years ago. There was also a phenomenon called the “Little Ice Age” from about the 1500s-1800. There is no good reason to believe that the temperature increases seen over the last half century are any recovery from that. And, in fact, one would still need to identify what natural “forcings” were causing such a temperature rise. And, one would further have to explain why the known forcing from the added CO2 and other greenhouse gases is not leading to a temperature rise. > [@](#): > > Also, I Believe that the CO2 measurements that were being taken (cited) were from the central Pacific while the levels being cited were based on cores taken from the poles. Could there be a possible discrepency between these numbers that could effect the overall results? > I’m pleading ignorance, so don’t beat me up! CO2 is well-mixed in the atmosphere. I.e., it doesn’t vary much from place to place (as long as one is not taking measurements too close to a direct source) as it only takes a few years for it to get spread around the global uniformly. There are some small seasonal variations in CO2 (due to the uptake of CO2 by plants during the spring and summer and release during the fall and winter, along with the asymmetry between the amount of vegetation in the Northern and Southern Hemispheres) and the strength of these seasonal variations varies somewhat from place to place. CO2 levels are now tracked at several places around the world and you can compare plots from various places, including the South Pole, [here](http://cdiac.ornl.gov/trends/co2/contents.htm). ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [December 30, 2006, 3:54am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/69 "2006-12-30T03:54:40Z")
[QUOTE=Baldwin] It honestly baffles me how a subject like this gets treated as if it were a political issue, not a question of science. [/QUOTE] Who was it who said . . . darn, can’t seem to find it online . . . “The law of gravity would be called into question if there were a commercial interest involved.” ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [December 30, 2006, 9:51am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/70 "2006-12-30T09:51:32Z")
[QUOTE=ralph124c] Geologists tell us that New England is rising at about 2-3" per century (the land is rebounding from being compressed by the ice cap that covered NE some 25,000 years ago). The island of Trinidad appears to be sinking: but geologists aren’t sure if this is due to the ocean level rising, or the land subsiding (the theory is that the sedimants of the Orinoco delta are compressing the seabed). Greenland will begin rising, as its ice cap melts off-the immense weight of the icecap (over a mile thick) has dpressed the island. So, how are we sure what is going on? I think you can find land rising and subsiing-it is not clear which effect is the dominant one. [/QUOTE] Geologist checking in: Yes, isostasy leads to rising and falling. As you noted the rates can be as high as several cm a century. But also as you noted, this is not a uniform effect. In some places there’s rise, in others, depression under sediment load. Consider that global sea level rise would be just that - thermal expansion and increased melt would lead to a rise of some sort _everywhere_, and at a far greater rate than isostatic rebound. There are terraines still rising from the last Ice Age, but we’re feeling the first rising effects of ACC right now. Those are way different timescales, and it’d be incredibly naive to think that isostatic rebound woul cancel out sea level rise. Also, a coupling of ACC-fed drought and topsoil dessication with ACC-fed superstorms or increased storm frequency would lead to increased erosion on continents, meaning while the continental interiors undergo more isostatic uplift because they no longer have to bear the mass of all that nasty topsoil, the coastal regions and shelf will have an increased sediment load, leading to increased isostatic depression. This could be seen as another (albeit slow) mechanism exacerbating sea level rise . ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [December 31, 2006, 11:58am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/71 "2006-12-31T11:58:09Z")
After another day of silence on this issue, I’m concerned that **Leaffan, intention, FRDE** and others might yet again leave a thread under the impression that they have somehow shown that Anthropogenic Climate Change is a sham which humanity can ignore. Time and time again, the fact that infra-red absorbing CO2 will reach concentrations of over 600 ppm this century without reducing our rate of emission seems to pass you guys by, unaddressed. For the third time, I ask you directly: Do you genuinely contend that such a concentration will have, as **Leaffan** puts it, “insignificant” consequences? I congratulate **intention** , at least, on clearly knowing his onions in terms of the extensive technical literature - he is certainly more informed than I am. But I cannot for the life of me follow how he can miss the absolutely central point about increasing infra-red-absorbing gas concentrations and conclude that, somehow, those concentrations will be nothing to worry about (and therefore nothing worth even attemtping to reduce _now_). **intention** , I’m sure you _can_ find examples of junk science and overstated claims in climatology. But I’m sure you could find such examples in evolutionary biology where you to become as well acquainted with the literature. Heck, I’m sure that the recent Holocaust conference in Iran turned up some examples of junk _history_ and sloppy methodology, too. But these examples do not impugn the central truths of climatology, evolution or the Holocaust. The concentrations of infra-red-absorbing gases are increasing very very quickly, and I simply cannot see how a _dangerous_ concentration will not be reached if we continue to dig up safe stores of greenhouse gases and release them. Or, is it the case that you don’t think anything _can_ be done, so we might as well not even _try_? If this is the case, and you _do_ accept the truth of ACC, then for crying out loud will you _say so_? It’s true that, so long as there are carbon stores in the ground to dig up, someone probably will do so if it’s economically advantageous. What we’re trying to do now is make it economically _dis_advantageous, _somehow_, at some point in the future. If you think that the economic negatives of any attempt whatsoever to reduce the emission rate are simply too great, on the assumption that such incredibly high concentrations will not be economically detrimental in any way, all I can say is … … I’m _skeptical_. ---
**Author:** ![FRDE](https://avatars.discourse-cdn.com/v4/letter/f/e68b1a/32.png) [@FRDE](https://boards.straightdope.com/u/FRDE)\ **Post date:** [December 31, 2006, 2:37pm UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/72 "2006-12-31T14:37:27Z")
Ok SentientMeat Can you explain how those huge reserves of plant derived hydrocarbons got there in the first place ? Could it be anything to do with photosynthesis ? Where did the atmospheric CO2 come from ? ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [December 31, 2006, 7:02pm UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/73 "2006-12-31T19:02:48Z")
**FRDE** : I am not sure what you are getting at. Yes, it is true that we are not driving CO2 to levels that are unprecedented in the entire history of the earth, only to levels that are likely unprecedented in the last ~20 million years (and thus, for example, in the history of our species). I suppose that you might find that reassuring in some odd way…but I hardly do. As someone commented in an apt and understated way on a blog that I was reading: “My house has been under 1000m of ice, at the bottom of a shallow sea, and in the middle of a large desert in geological time; all of these things lower property values, so I don’t want them to be repeated.” ---
**Author:** ![fessie](https://avatars.discourse-cdn.com/v4/letter/f/c37758/32.png) [@fessie](https://boards.straightdope.com/u/fessie)\ **Post date:** [December 31, 2006, 7:20pm UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/74 "2006-12-31T19:20:53Z")
> [@The Independent](#): > > Review of the year: Global warming > Our worst fears are exceeded by reality > By Steve Connor > Published: 29 December 2006 > > It has been a hot year. The average temperature in Britain for 2006 was higher than at any time since records began in 1659. Globally, it looks set to be the sixth hottest year on record. The signs during the past 12 months have been all around us. Little winter snow in the Alpine ski resorts, continuing droughts in Africa, mountain glaciers melting faster than at any time in the past 5,000 years, disappearing Arctic sea ice, Greenland’s ice sheet sliding into the sea. Oh, and a hosepipe ban in southern England. > > You could be forgiven for thinking that you’ve heard it all before. You may think it’s time to turn the page and read something else. But you’d be wrong. **2006 will be remembered by climatologists as the year in which the potential scale of global warming came into focus. And the problem can be summarised in one word: feedback.** > > During the past year, scientific findings emerged that made even the most doom-laden predictions about climate change seem a little on the optimistic side. **And at the heart of the issue is the idea of climate feedbacks - when the effects of global warming begin to feed into the causes of global warming. Feedbacks can either make things better, or they can make things worse. The trouble is, everywhere scientists looked in 2006, they encountered feedbacks that will make things worse - a lot worse.** > > Next year, the UN’s Intergovernmental Panel on Climate Change (IPCC) will publish its fourth assessment on the scale of the future problems facing humanity. Its last assessment, published in 2001, had little to say on the subject of climate feedbacks, partly because, at that time, they were such an unknown quantity. This year, scientists came to learn a little more about them, and they didn’t like what they learnt. > > During the past two decades, the IPCC has tended to regard the Earth’s climate as something that will change gradually and smoothly, as carbon dioxide and global temperatures continue their lock-step rise. But there is a growing consensus among many climate scientists that this may be giving a false sense of security. They fear that feedback reactions may begin to kick in and suddenly tip the climate beyond a critical threshold from which it cannot easily recover. > > Climate feedbacks could turn the Earth into a very different planet over a dramatically short period of time. It has happened in the past, scientists say, and it could easily happen in the future given the unprecedented scale of the environmental changes caused by man. > > \*\*There are two types of feedback that can play a role in the future direction of the Earth’s climate. The first is a “negative” feedback, which is largely good for us, because it works against things getting worse. The classic example of a negative feedback is the fertilising effect of carbon dioxide. As concentrations rise, then so does the amount of carbon absorbed by the higher growth rate of plants. The result is a negative feedback that tends to check rising levels of carbon dioxide. > > A “positive” feedback makes things worse by adding to the existing problem. It brings about a vicious circle, in which a rise in carbon dioxide or global temperatures causes some change in the climate system which, in turn, leads to further rises in carbon dioxide or temperatures. > > A classic example of a positive feedback is the melting sea ice of the Arctic. As temperatures rise, the ice floating on the Arctic sea melts, exposing dark ocean where once there was white ice that reflected sunlight, and heat, back into space. The newly revealed dark ocean absorbs more sunlight and heats up, causing more ice to melt, and so reinforcing the positive-feedback cycle.\*\* > > But even this simple description belies the true complexity of life on Earth. In fact, there is a negative feedback at work as well with Arctic sea ice, which insulates the underlying ocean and keeps it warmer during the cold, dark northern winters. However, on balance, it is the positive feedback that dominates here, as it does in several other instances investigated by scientists in 2006. > > “The main concern is that the more we look, the more positive feedbacks we find,” says Olivier Boucher, a climate scientist at the Met Office. “That’s not the case when it comes to negative feedbacks. There seems to be far fewer of them.” The sentiment is echoed by Chris Rapley, the director of the British Antarctic Survey in Cambridge: “When we look at the list of all the feedbacks in the climate, the list of positive feedbacks is worryingly long - a lot longer than the negative feedbacks. To be honest, it’s a wonder that the climate has remained so stable.” > > Let’s stick with Arctic sea ice a bit longer before looking at other issues that emerged 2006. In March, Nasa satellites monitored a 28-year record low for winter sea ice. Normally sea ice recovers during the long Arctic winter, but this was the second consecutive year that the ice failed to re-form fully to is previous winter extent. > > This meant there was less ice at the start of the northern summer, with the result that last September saw the second monthly minimum for summer sea ice - almost hitting the record minimum set in September 2005. > > During the past four or five years, there has been an acceleration in the rate at which sea ice is melting, a change that some scientists put down to a positive feedback. “Our hypothesis is that we’ve reached the tipping point,” says Ron Lindsay of the University of Washington in Seattle. “For sea ice, the positive feedback is that increased summer melt means decreased winter growth and then even more melting the next summer, and so on.” > > Professor Lindsay likens the positive feedback in the Arctic to a ball that has begun to roll down a slope, gathering momentum and speed as it goes. In order to reverse the direction of movement, the ball has to be pushed back up the slope. But how? “Perhaps a cooling period could reverse the situation,” he says. “But with global warming, temperatures are only bound to rise.” > > **While we are in the northern hemisphere, take a look at another positive feedback that scientists investigated in 2006. This is connected to the frozen permafrost of Siberia and northern Canada, which lock up vast stores of carbon in the form of methane, a gas formed by the decomposition of organic matter. For more than 12,000 years, this methane - a greenhouse gas 20 times more potent than carbon dioxide - has been safely stored under the permanently frozen ground. But now the permafrost is melting and the gas is bubbling free into the atmosphere.** > > Sergei Kirpotin, a botanist at Tomsk State University in Russia, has been studying the extent of the melting permafrost of Western Siberia, the site of the world’s biggest frozen peat bog. During the past few years, he has watched lakes getting bigger and bigger as the solid permafrost underneath liquifies. > > Normally, patches on white lichen on high Siberian ground reflect the sun’s rays and help to keep the ground underneath cold. But as the dark lakes expand, more heat is absorbed and more permafrost melts. “As we predicted in the early 1990s, there’s a critical barrier,” says Professor Kirpotin. “Once global warming pushes the melting process past that line, it begins to perpetuate itself.” > > **The once-frozen peat bogs of Siberia - bigger than France and Germany combined - began to “boil” furiously in the summer of 2006 as methane bubbled to the surface. Exactly how much is being released into the atmosphere is unknown, although some estimates put it as high as 100,000 tons a day - which means a warming effect greater than America’s man-made emissions of carbon dioxide.** > > But Katey Walter of the University of Alaska believes even this could be seriously underestimated. In a study published in Nature in September, Walter and her colleagues calculated that the level of methane emissions from Siberia could be anywhere between 10 per cent and 63 per cent higher than anyone had hitherto suspected. “We have shown that the North Siberian lakes are a significantly larger source of atmospheric methane than previously recognised,” she says. > > \*\*So the message is clear: frozen peat bogs that turn into heat-absorbing lakes release methane, which means a stronger greenhouse effect and higher temperatures, leading to more permafrost melting. The cycle was clearly documented in 2006 but just how strong this positive feedback turns out to be has yet to be fully determined. > > Another study in 2006 looked at perhaps the most important climate feedback there is. Yet it went unreported - so listen up. The Earth has been a very accommodating planet. During the past 200 years, it has absorbed more than half of all man-made emissions of carbon dioxide through natural carbon “sinks”, mostly in the ocean but also on land. The rest of the emissions have been left in the air to aggravate the Earth’s natural greenhouse effect, so raising global average temperatures.\*\* > > But what if something were to interfere with these very useful carbon “sinks”? Can we forever rely on them to remain sinks, or could they turn into dangerous sources of atmospheric carbon? A huge international team of climatologists asked these questions in a little-known study published in the July issue of the Journal of Climate. The conclusion makes depressing reading. > > The scientists investigated what would happen if they tinkered with 11 of the world’s biggest computer models of the complex climate-carbon cycle. They wanted to simulate what would happen to the carbon sinks on the land and the ocean for each model as the world gets warmer. All the models agreed that as the world heated up, the ability of the land and the oceans to keep on absorbing carbon as efficiently as they have in the past 200 years gets appreciably worse. > > In other words, we cannot rely on planet Earth to be so accommodating in terms of mopping up half of our carbon pollution. But could something even worse happen? Could these carbon sinks turn into carbon sources? The answer is yes. Many models suggest that the terrestrial biosphere could become a net carbon producer by the mid 21st century. Signs are that it is already happening in some parts of the world. > > Guy Kirk of the National Soil Resources Institute at Cranfield University found that the soil of Britain is releasing more carbon dioxide into the atmosphere than a quarter of a century ago because increasing temperatures are speeding up the rate of organic decay. “It’s a feedback loop,” says Professor Kirk. “The warmer it gets, the faster it is happening.” In fact, he estimates that since 1978, Britain’s soil has released on average an extra 13 million tons of carbon dioxide a year, which is more than the 12.7 million tons a year Britain saved by cleaning up its industrial emissions. > > **The outlook does not look any better out at sea. The important carbon sinks of the ocean are also suffering from feedback. As more carbon dioxide dissolves in seawater to form carbonic acid, the acidity of the ocean increases - the rate is 100 times faster than at any time for millions of years.** > > There is a physical feedback - it is just harder for more carbon dioxide to dissolve in acid water - as well as a biological feedback. Tiny organisms called coccolithophores use dissolved carbon to make their shells, but acidic seas make this more difficult. This blocks an important biological pump that pushes carbon to a long-term store on the seabed - which is what happens when billions of tiny shells sink to the depths as coccolithophores die. > > Yet another ocean feedback was monitored in 2006, this time involving phytoplankton, the tiny microscopic plants of the sea that form the basis of the entire marine food chain. Nasa satellites showed earlier this month that phytoplankton - which absorb carbon dioxide - are finding it harder to live in the more stratified layers of the warmer ocean, which restrict the mixing of vital nutrients. Since 2000, when the sea surface temperatures began to rise more noticeably, the photosynthetic productivity of phytoplankton have decreased in some ocean regions by 30 per cent. > > **“As climate warms, phytoplankton production goes down, but this also means that carbon dioxide uptake by ocean plants will decrease,” says Michael Behrenfeld of Oregon State University. “That would allow carbon dioxide to accumulate more rapidly in the atmosphere, making the problem worse.” Some climate scientists believe that the risk of dangerous feedbacks tipping the Earth’s climate system beyond a threshold is so great that there should be wider recognition of what they term “abrupt changes”. The point is, they say, it has happened repeatedly in the past. It happened 55 million years ago when a trillion tons of methane were suddenly and mysteriously released from frozen stores on the seabed, causing global temperatures to soar 10C, and a mass extinction of species.** > > It happened 14,500 years ago when ice sheets catastrophically collapsed into the ocean causing sea levels to rise by 20 metres in just 400 years. And it happened 6,500 years ago when the Sahara was suddenly turned from lush vegetation to dry desert. > > Scientists say that what is happening now to the planet in terms of carbon dioxide levels and global temperatures is just as abrupt as anything that has occurred in the past. “What we are doing now to the Earth is unprecedented,” says Professor Rapley of the British Antarctic Survey, “so we cannot rule out the possibility that we are doing something that will create a strong positive feedback, which will push the Earth into a domain where things will happen that have never happened before.” I know this is a little long vis a vis copyright issues, but there is a whole lot more to the article; I didn’t want to take a chance on distorting it by chopping out bits and pieces. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [January 1, 2007, 7:35am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/75 "2007-01-01T07:35:09Z")
[QUOTE=SentientMeat] Incidentally, **intention** , [last time](http://boards.straightdope.com/sdmb/showthread.php?t=369967&page=1&pp=50) we discussed climate change:[ul][li]I, unforgivably, thought one of Africa’s largest lakes was in Fiji, while[/li][li]You, intriguingly, proposed that some mechanism will kick in this century which will absorb all the excess CO2 we’re currently emitting, such that the increase will fall from +2.5 ppm per year to (presumably) zero and the concentration will stabilise at some level above 400 ppm. [/ul] My unforgivable ignorance is now vanquished. Do you still stick to your proposal (and if so, can we explore it again)?[/li][/QUOTE] I lost this discussion off my radar for a while, so I have some catching up to do. I did not propose that “some mechanism will kick in this century”. I pointed out that as the CO2 concentration in the atmosphere has risen every year, so also the amount of CO2 sequestered by the planet has increased every year. This is an example of Le Chatelier’s Principle, and is well known to be modeled by an exponential decrease in the amount of the relevant component, in this case CO2. This is shown by comparing the amount of CO2 emitted by the amount remaining in the atmosphere. Currently, the planet is absorbing about 3 gigatonnes of additional carbon per year (~ 6 Gtonnes are emitted annually, about 3 Gtonnes remain in the atmosphere, the rest is sequestered). Obviously, this number has risen since pre-industrial times. Get the numbers, do the math. One of the curiosities about an exponential decay is that given a stable input, an equilibrium point is reached when the amount of the decay equals the amount of the input. Consider a pool with a drain being filled by a large hose. At first, the hose puts in more water than flows out. But as the pool fills higher and higher, the pressure on the outlet increases and the water flows out faster and faster. At some point, they are equal, and the pool will not fill any more. In other words, as I said before, if emissions stabilize, atmospheric concentrations will not continue to rise indefinitely. Glad to hear about the lake in Fiji, however, and now all of your ignorance is vanquished. w. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [January 1, 2007, 8:22am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/76 "2007-01-01T08:22:07Z")
[QUOTE=ITR champion] Gee, that article actually says that they’re taking action in the Maldives both because of coral reef destruction and because of rising sea levels. It always helps to read your cites before you link to them, otherwise you may end up embarrassing yourself. Furthermore, it should be noted that coral reefs aren’t vanishing solely due to physical destruction. [They’re also being damaged](http://www.time.com/time/magazine/article/0,9171,1050329-5,00.html) by rising sea temperatures, a.k.a. global warming. [Here’s more](http://www.cmaj.ca/cgi/reprint/163/6/729.pdf) linking global warming to the issues in the Maldives. So in short, it looks like you’ve confirmed my claim that the Maldives are already taking action, evacuating islands and building barriers because of global warming. Thank you. We should also note that it’s not just the Maldives. There’s also the nation of Tuvalu in the central Pacific. [(From here.)](http://itotd.com/articles/499/disappearing-island-nations/) It’s true that I don’t have a cite for my facts. I have many cites, unlike some people. I asserted that they’re in the process of evacuating some islands; we now have multiple separate cites that back that up. Do you have some evidence backing up your claim that no evacuations have taken place, or are you willing to withdraw your claim? Incorrect. Your hypothesis in wrong. Far from knowing that the basis of my beliefs is wrong, I have proved beyond doubt that the basis of my beliefs is entirely correct. I, however, am not so naive as to believe that _you_ will change your opinion just because you’ve seen the facts. [/QUOTE] I did read the article on the Maldives. While they made the claim that it was also from sea level rise, they presented no evidence to back it up. They did provide evidence, on the other hand, that the reefs have been destroyed. Regarding sea level rise, if you have any evidence that the sea level rise in the Maldives has shown any sign of change from its historical rate, bring it on … if not, you might reconsider your claim. Remember also that a coral atoll exists in a balance between wind (tearing it down) and reef growth (building it up). It is a delicate balance, and easily disturbed. Cutting down trees (an ugly habit of humanoids) for example can kill an atoll just as surely as destroying the coral. Finally, the Maldives were hard hit by the New Years tsunami. It’s easy to say “it’s from sea level rise”. I do not consider that a random person making that claim establishes anything. Take Tuvalu as an example. The whole furor over Tuvalu was started by a long article in the Sierra Club magazine about how Tuvalu was hit so hard by rising seas that a missionary’s cabin, that had stood for over 100 years, had been eaten away by rising sea levels. But upon closer examination, it turns out that a SOPAC study had clearly established the reason for the missionaries cabin’s demise. It was humans, all right, but it was because in WWII, the US Navy cut through the outer reef to bring in ships to the island. The changing currents ate away the island until the missionaries cabin fell. See Xue, C. (1996) Coastal Erosion And Management Of Amatuku Island, Funafuti Atoll, Tuvalu, 1996, South Pacific Applied Geoscience Commission (SOPAC). Based on this totally bogus claim, which was highly hyped by the media and folks like yourself, Tuvalu conned Australia into allowing them to emigrate there … a neat deal, but I fear it proves nothing except that there are suckers on every continent. If you think Tuvaluans moving to Australia is a sign of sea level rise, you don’t know anyone from Tuvalu … I do. A large number of them would love to emigrate, and will take any opportunity. Nobody in Tuvalu has been “evacuated”. So when you read a claim by some journalist somewhere that an island has died from sea level rise, remember the missionaries cabin, and don’t rush to credulity. Did you see the screaming headines in the [article](http://news.independent.co.uk/environment/article2099971.ece) the other day, about Lohachara Island being lost to sea level rise? I suppose you believed that one as well. A bit of research turns up the fact that it was an island in the delta of the river system that drains half of India and the Himalayas, that was subjected to annual flooding, shifting river channels reducing the annual silt addition that kept it above water, loss of freshwater, clearcutting, and recurrent typhoons … and that it washed away 22 years ago … The UNEP description of the region is telling: > [@](#): > > The land is moulded by tidal action, resulting in a distinctive physiography. An intricate network of interconnecting waterways, of which the larger channels of often a mile or more in width run in a generally north-south direction, intersects the whole area. Innumerable small khals drain the land at each ebb. Rivers tend to be long and straight, a consequence of the strong tidal forces and the clay and silt deposits which resist erosion. Easily eroded sands collect at the river mouths and form banks and chars [low, inundation prone riverine islands such as Lohachara, which is actually called “Lohachara Char”], which are blown into dunes above the high-water mark by the strong south-west monsoon. > > Finer silts are washed out into the Bay of Bengal but, where they are protected from wave action, mud flats form in the lee of the dunes. These become overlain with sand from the dunes, and develop into grassy middens. This process of island building continues for as long as the area on the windward side is exposed to wave action. With the formation of the next island further out, silt begins to accumulate along the shore of the island and sand is blown or washed away (Seidensticker and Hai, 1983). Apart from Baleswar River the waterways carry little freshwater as they are cut off from the Ganges, the outflow of which has shifted from the Hooghly-Bhagirathi channels in India progressively eastwards since the 17th century. They are kept open largely by the diurnal tidal flow (Seidensticker and Hai, 1983). [Source](http://www.unep-wcmc.org/sites/wh/sundarb.html) Islands have been formed and destroyed in that river since time immemorial. Coral islets have been formed, changed shape, built up, been washed away, reformed or not, for millennia. Now you, or any journalist, can make the claim that it’s all due to sea level rise. Me … I prefer facts. Regarding the coral bleaching, yes, I noted that in your cite, it happened. Having lived on tropical islands for many years, I’ve seen it happen myself. It is undoubtedly from warm water. The world has been warming for a couple centuries now. Does coral bleaching surprise you? Having lived in the tropics, I’ve also seen the coral re-grow in a short time (from a couple years to a decade). It is how coral adapts to increasing temperatures. Your claim, however, was not about warm water, it was sea level rise. w ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [January 1, 2007, 8:46am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/77 "2007-01-01T08:46:07Z")
[QUOTE=SentientMeat] Time and time again, the fact that infra-red absorbing CO2 will reach concentrations of over 600 ppm this century without reducing our rate of emission seems to pass you guys by, unaddressed. For the third time, I ask you directly: Do you genuinely contend that such a concentration will have, as **Leaffan** puts it, “insignificant” consequences? [/QUOTE] Oh, please. Future concentrations of CO2 are not facts. They are projections, or scenarios, or forecasts, but they are not facts. Please learn to distinguish facts from other types of information, your life will be much less stressful. Nor is 600 ppmv even a reasonable forecast. All of the B scenarios of the IPCC are below that level, and even those are based on highly questionable economic scenarios. In addition, they all assume larger emission rates than the present, while you have specified our current rate of emission above. Would a CO2 level of 0.6% have only “insignificant” consequences? The truth is, we don’t know. Here’s one way to look at it. Without the greenhouse effect, the temperature of the earth would be about 19° lower. The total greenhouse downwelling radiation is about 325 watts/m2. This means that each watt/m2 has warmed the earth by about a tenth of a degree. Let’s double that to be on the safe side. Current CO2 level is about 380 ppmv, increase is 3.7 w/m2 time log2(600/380) = 2.5 w/m2 = half a degree. We had half a degree warming in the 20th century without significant effects. w. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [January 1, 2007, 8:49am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/78 "2007-01-01T08:49:18Z")
[QUOTE=ITR champion] Traditionally sea levels are measured relative to benchmarks on nearby landmasses. Now we also have several satellites capable of mapping sea levels, and those obviously don’t depend on the landmasses remaining fixed. [See here](http://sealevel.colorado.edu/) for in-depth discussion and a graph of global average sea level over the past twelve years. Feel free to compare that graph with Michael Crichton’s claim that there’s “no clear trend” in sea level data. [/QUOTE] Could you post a citation to the Michael Crichton claim? IIRC, he said that there was no increase in the _rate_ of the sea level rise, which is borne out by the satellites. I doubt if he said there was no rise in sea level, but I’m willing to be surprised. w. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [January 1, 2007, 10:35am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/79 "2007-01-01T10:35:59Z")
SentientMeat, you seem to be confusing laboratory results from a given change with the effects of the same change on a complex system. You believe that, since increasing CO2 in the lab ups the temperature, that it will do the same on the earth. It’s simple physics, case closed. The problem is, the global temperature is a measurement of a complex dynamic system, with loads of known and unknown feedbacks. This complicates a simple problem immensely. To illustrate what I mean, consider taking a block of aluminum six feet (2 m.) long and putting one end in a bucket of hot water. Put a thermometer in the other end of the aluminum block, keep the water hot, and in short order the thermometer starts to rise. It is a simple problem, well defined, just physics. Works in the laboratory, must work in the real world, case closed. Now let’s replace the block of aluminum with a complex dynamic system with loads of known and unknown feedbacks … oh, lets say a human being. You can put their feet in a bucket of hot water, and put a thermometer in the other end … but you’ll wait a long, long time for a temperature rise. That’s why predicting the global temperature as a function of CO2 concentration is not a simple problem as you assume. The climate is a chaotic, multi-stable, resonant, driven, optimally turbulent, constructal tera-watt scale heat engine, with dozens of known and unknown forcings and feedbacks. There are five main subsystems (ocean, atmosphere, cryosphere, lithosphere, and biosphere), each of which affects the others, and each of which has internal resonances and feedbacks. None of these systems is fully understood. As an example, the earth (lithosphere) is always interchanging momentum with the ocean and atmosphere. This exchange of energy is large enough that it actually speeds up and slows down the rotation of the earth, changing the length of the day (LOD). As far as I know, no GCM includes this effect. But it is huge, and significant for the climate. Here’s a [graph](http://www.fao.org/docrep/005/Y2787E/y2787e03b.htm#FiguraB) of the relationship from the well known denier organization, the United Nations FAO. How does the change in LOD affect the climate? We don’t know. How does a change in CO2 affect the LOD? We don’t know. In fact, there are hundreds of questions about the climate to which we can only say, we don’t know. Does this mean we should do nothing? Absolutely not. This is a much wider question than just CO2, because all of the doomsday evils foretold by climate alarmists are with us today. Droughts? We have extra, no shortage there. Floods? Check with Bangladesh, they might have some to spare. Hurricanes? See 2005. Rising sea levels? Go talk to Holland. Disease? Chat with some Africans. Hot spells? Yep, aplenty. Warming earth? Been with us for three centuries. Will any given one of these increase in the future? Quite possibly, but the ugly truth is, we don’t know. Should we just “hope for the best”? Nonsense. Should we worry about the year 2100? We don’t have enough knowledge to do that, and besides, we have pressing problems and limited money. The best thing we can do about future climate problems, our best defense, is to deal with the current climate problems. The more we know about solving current droughts, the better we will be able to deal with future droughts … and the same is true about hurricanes, floods, and all of the vagaries of the natural world. w. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [January 1, 2007, 10:50am UTC](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737/80 "2007-01-01T10:50:22Z")
[Above](http://boards.straightdope.com/sdmb/showpost.php?p=8107844&postcount=77) , working fast from memory, I said that without the greenhouse effect, the earth would be 19° cooler. Actually, it would be 19°C below zero … brrr. In fact, it is at about 14°C or so, a difference of about 33°C The downwelling (greenhouse) infra-red radiation [averages](http://www.junkscience.com/Greenhouse/RadiationBudget.pdf) 325 watts/m2. This gives a correct temperature sensitivity of: Sensitivity (°C per watt/m2 forcing) = 33°C/325 w/m2= 0.1°C per watt/m2. In my calculation above I used twice this figure, for good measure, so my conclusions were correct, (half a degree increase from 600 ppmv CO2) even though my calculations were not. [Previous page](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737.md?page=3) [Next page](https://boards.straightdope.com/t/climate-change-in-our-lifetime/385737.md?page=5)