Encyclopedia > Talk:Global warming OldTalk
Talk:Global warming/OldTalk
I would like to preface my comments with the fact that I am not an expert in this area. Nevertheless I am quite troubled by the 2nd paragraph.
The paragraph states that throughout history the earth's temperture has varied by about 3 degrees c. Well - this is NOT the case. Up until the end of the precambrian the earth was rather cool and since that time - for the last 600 million year it was about 10C warmer than today for probably about 3/4 of the time span. In fact we appear to be at the beginning of a warming trend that started about 2 million years ago or so.
I shall refer to this rather excellent website for the following comments: www.scotese.com "The Paleomap Project"
The Precambrian was rather cold - read about the tillites in southern Australia - Australia was at the equator when these were deposited. During this time the earth had high levels of CO2. It would have been about 600 million years before the end of the precambrian when CO2 started to get scrubed from the atmosphere by photosynthesis.
Please refer here for information on atmospheric CO2 concentrations over the last 4.5 billion years.
http://www.scotese.com/precamb_chart.htm
As you can see at one time CO2 was about 80% which then dropped to about 15% by 2,700 million years when photosynthesis developed. The primative photosythesis which evolved at this time was robust enough to scrub the CO2 levels from 15% to less than 1% by the end of the precambrian. CO2 levels have never gone back up.
http://www.scotese.com/climate.htm shows the change between "ICE HOUSE" and "HOT HOUSE". If drawn to scale it actually shows about a 70 ma cycle. The present warming started at the end of the Tertiary.
To say that _any_ of this is linked to green house gasses is really stretching things IMHO.
I think global warming should take a very long view. History did not start when mankind started to record it. In recent times - there have been warm and cool periods - this over 100's of years. But really CO2 and other greenhouse gases have only been introduced very recently.
Probably earth will warm up. Very probably because usually it has been warm - for 100's of millions of years. Very likely this will have nothing to do with mankind.
terrell: terr@terralogic.net
- The "history" that is being talked about is recorded history -- Yes it is ambiguous so I will change it. However your statement "But really CO2 and other greenhouse gases have only been introduced very recently." is false. You yourself indicate that CO2 has always been part of the atmosphere and there have been several periods within intense warming that have followed the release of CO2 from methane hydrate deposits -- most notably during the Miocene 55 million years ago that was followed by extensive evidence of an extreme warming event [1] (http://earthobservatory.nasa.gov/Newsroom/MediaAlerts/1999/19991119778). This warming occurred on a human timescale and has left its chemical signature in sediments and in the shells of animals. You are correct in stating the the late precambrian was cooler than today. However, what you obviously don't know is that the sun at that time of Snowball Earth was 30% less luminous than it is now. The reason why the earth froze over was due to the sudden (in geological terms) drop of CO2 concentration in the atmosphere that was caused by an explosion of photosynthetic bacteria that consummed CO2 at a faster rate than aerobic bacteria and volcanos could produce it. CO2 has been dropping, on average, over the timespan of hundreds of millions of years because the sun has been increasing its solar output (this is self-regulating on this timescale: lots of CO2 = hot temps = lots more plants that are buried before decaying = less CO2). CO2 alone does not control the climate -- solar input, ocean circulation, orbital motions along with the carbon cycle are all the major factors that control climate. The only debate is the amount of the current global warming has been caused by human activities vs. the amount of background warming that one would expect after coming out of the most recent glacial maximum 15,000 years ago. We do know that CO2 levels have increased by 30% since pre-industrial times and we also know that almost all of that increase is from the burning of fossil fuel. We also know that CO2 is a heat-trapping gas and high concentrations of this gases are strongly correlated with warming events in the geologic past and cooling events equally correlated with low [CO2]. It doesn't take a rocket scientist to put two and two together. BTW, we place our comments at the end of talk pages here and we also don't change what others have said (noting the oddness you added to Tim's statement). --maveric149
1) thanks for the tip on etiquette. I saw nothing in the Faq about this. Also, I did not intentionally edit Tim's statement. There was a weirness going on and for some reason the browser (opera 6.0) was acting rather strangely. Thanks for fixing it up... I checked the diff's and I see what you are refering to.
2) 55ma places us at the end of the paleocene. My geology texts put the miocene between 12ma and 25ma. I see this is in contrast to the 2-24 in the wikipedia artical. My reference: Dunbar&Waage p16 sbn 471 22507
How long and how well documented is the 55ma warming event? I note that the present cooling started about 1/2 way through the Cenozoic - and that the last 5 ma have been abnormally cool. This cooling trend seems to be reverting for the last 2ma.
3) I'm aware of the factors involved in the warming/cooling trends. But this is not well covered in the artical. I think it should be.
4) Earth was 10C warmer than now for about 400ma or more of the last 600ma.
5) I agree that green house gasses definately work in the lab. But co2 levels are very very low at only about 0.035%. A chemical engineer designing a scrubber would have great difficulty trying to scrub flue gasses to such a low level - yet plants derive all of their carbon from this source (ie it is a nutrient).
7) I think the artical should try to place things into context better. The development of photosynthesis in the precambrian for instance spans a period of time about equal to all the geological history from the explosion of life in the cambrian to the present.
I don't think there was a "sudden drop". I think this drop took 100's of millions of years. During this time the earth was slowly warming up so that by the cambrian it was about 10C warmer than today. This is a trend directly opposite the hypothesised effect of CO2.
In any event - the artical seems to be focused on the last few 1000 years. I agree this is the period of most interest to mankind. But even 15,000 years is only 1/40,000th of the time of the phanerozic era.
Somehow this is important. On the one hand we have the age of the dinosaurs spanning about 100,000,000 years and the earth is warm during this whole period then cools off for about 25 million years to a level about 5C greater than today then back up to +10 for another 100,000,000 years.
Then it drops about 5 million years ago and seems to start warming up 2 million years ago.
We contrast this with events that occur on a scale of a couple 100 or at best a few 1000 years.
It seems unlikely that greenhouse gasses could cause the climate shifts of the past. Something else is at work. Even solar output doesn't explain it unless we've had shifts in the solar output that carry on for 50 million years or so.
So all I'm saying is that somehow I think the artical should embrace the problem. We have huge long term warming and cooling trends that span millions of years and are several times larger than the events that might be occuring now.
Its like being in a rowboat in the middle of the ocean being buffeted by waves and winds and storms and somehow trying to extrapolate where we are going. The problem with this analogy is that given a good enough inertial guidance system one could actually determine where we are going!!
So by this same analogy my opinion is that it is not sufficiently demonstrated that we really do know enough about the effects of greenhouse gasses and so forth to be able to suggest that anything we might be doing on planet earth is anything more than a really small blip.
I think I would be happy if somehow we could write a preamble that draws a time line for 4.5 billion years and traces the paleoclimatology just as Scotese did and on this same scale shows what we know about the paleoatmosphere and other significant events. Then we can draw a little arrow to the present and talk about what we presently believe.
terrell: terr@terralogic.net
Terrell, thank you for your long discussion of the global warming article. I like many of your suggestions. Feel free to edit the article in any way you see that would improve it.
It is not necessary to gain agreement from other contributors before making an edit. Just make sure that whatever you put in is backed up by a reasonable reliable source, such as a published article by a researcher in the field.
The accepted formula is: A said B about C. When there is substantial disagreement, we generally add: D disagrees with B because of E. -- Ed Poor
Terrell -- much of what you proposed would probably be better in global climate change and not global warming. You are talking about large-scale fluctuations in temperature that have occurred throughout history -- not just global warming. However, most data suggest that the Cenozoic cooling is primarily due to changes in ocean circulation that occurred as a result of A) the formation of the Isthmus of Panama[?] (thus blocking off ocean circulation from the Mid-Atlantic and Pacific, B) the emplacement of Antarctica at the south pole (thus promoting the formation of continental glaciation there and resulting in increased reflection of solar heat back into space), and also probably due to variations in orbital motion and axial tilt. However, on top of this is a very strong correlation of CO2 concentration and the severity of cold/warm snaps -- being low in concentrations during glacial maximums and much higher in glacial minimums (such as we are now living) and very high in non-glacial periods (such as the late Paleocene to early Eocene hothouse -- thanks for catching that, BTW). CO2 does seem to be the top suspect in this warming event. We see direct evidence for more recent CO2-mediated climate change in gas trapped in ice core samples dating back about 200,000 years. So yes, like I said before, there are large-scale changes that tend to affect the climate more than CO2 alone over vast expanses of geologic time. However, it is the smaller scale and shorter-lived changes that concern scientists -- CO2 is far more important in this area (it takes many tens of millions of years to have significant changes in solar output due to stellar evolution and equally long periods of time for plate tectonics to change how ocean currents flow). Changes due to CO2 levels work on the scale of hundreds to thousands of years. --maveric149
I feel a bit of a concensus. I just checked - there is no page on paleoclimatology. I have created one and I request people to have a look. It is just a very rough stub at this point.
Terrell: terr@terralogic.net
I just reorganized the page considerable. I didn't delete anything, except repetions, of which there were many. Many paragraphs appeared in the wrong section, for instance a mention of anthropogenic factors in the section about "Natural factors". The article now also cleanly distinguishes between the models designed using past data to establish the relative importance of the various factors, and the predictive models based on several scenarios. AxelBoldt, Thursday, May 23, 2002
- Thanks, Axel! Great job! Now the article flows in one continuous narrative, like something from Time magazine. I couldn't have done it better myself, which obviously is why not I but YOU did!! Ed Poor, Friday, May 24, 2002
After my latest revision of the opening several paragraphs, I couldn't figure out where to put this passage:
- Secondary evidence comes from observed variations on the snow cover and ice extent, global average sea level, precipitation, cloud cover, El Nino and extreme weather events during the 20th century.
What are these variations deemed "evidence" of?
- Evidence that the atmosphere got warmer in the last century and a half? No one is disputing that.
- Evidence that the global warming hypothesis (advocated by Kyoto Protocol proponents) is true?
For example, if a particular IPCC model is true, we should see X degress of warming per decade at the surface, or in the troposphere (hypothesis). Then, present the observations: this group of scientists reports this amount of warming per decade, that group reports that amount. Finally, we report the analysis of the various scientists who have compared the theoretical predicitions to the actual observations.
This is the scientific method, right? Do all agree?
If so, please help me finish this article according to the plan I have outlined.
If not, please explain where I have gone wrong and present a better alternative plan for improving this article.
Ed Poor, Wednesday, June 12, 2002
The "secondary evidence" that you removed is evidence for the current warming period, as the headline "Evidence for a current warming period" clearly stated. Of course, if you change the headline, the paragraph won't fit anymore. Any article about "Global warming" should start with a paragraph about the fact that currently a global warming period is going on, and the undisputed evidence for that. There is no controversy about the current warming period. I don't know why you like controversies so much. Carbon dioxide has absolutely nothing to do in this section.
Why did you completely change the beginning of the article again even though you agreed before that the article was better than you could possibly have written it? I get the impression that you just agreed with me for tactical reasons, then decided to come back acouple of weeks later and hoped no one would notice.
In the first paragraph, you say "there's considerable controversy of this issue". About what issue? Current global warming? No. That humans have an impact? No. That the greenhouse effect exists? No. The controversy is solely about how big the human impact is among the many factors that influence global climate. I also don't know what "global warming hypothesis" you are talking about. And I don't agree that this article should be about that hypothesis, whotever it may be.
I don't see how to fix the article except for reverting. Please discuss specific problems you have with the current article here. AxelBoldt, Wednesday, June 12, 2002
I didn't hope you wouldn't notice; actually, I'm rather glad you did notice although I wish you had discussed before reverting.
The "global warming hypothesis" presented by the IPCC and other advocates of the Kyoto Protocol is:
- the earth's atmosphere is warming up too much
- men are causing a significant amount of this warming
Would you please explain (here, or better yet in the body of the article) how "snow cover and ice extent, global average sea level, precipitation, cloud cover, El Nino and extreme weather events" are evidence for global warming? Note that I am not arguing with you: I just think the article would be better with a clear explanation of what these phenomena are evidence of, and who thinks so, and why.
Ed Poor, Wednesday, June 12, 2002
I am not good at writing long, cohesive documents. My strength lies rather in comparing what one person says with what another person says. This enables me to see readily that many people, including the overwhelming majority in the mass media, support the Kyoto Protocol and the other UN initiatives: IPCC, UNEP, and so on, despite many individual scientists who claim that Kyoto and the UN are in error.
I believe my grasp of scientific and statistical principles is sufficient for me to see (at least) that there is considerable disagreement between two opposing camps. Whether this disagreement amounts to a "controversy" or not, it certainly exists.
What compromise can we make? May I say that there is a controversy? If not, may I at least say things like "According to the IPCC, there is a consensus" and "Mr. X in the Clinton Administration said, 'the science is settled'"? May I mention that a lead author of the IPCC's 1995 report said that the policymakers had the final say on what went into it, and that half the scientists disagreed with it?
I don't know what else an article on global warming should be on, if not the hypothesis that people are making the earth's atmosphere warm up too much.
Many advocates believe that hypothesis, so the article should explain
- why they believe the hypotheses
- what they propose to do about it
- the progress they've made to date
Many other advocates dispute that hypothesis, so the article should also explain why they are skeptical:
- Some scientists say there is "no discernible human influence" on global atmospheric temperature
- Some scientists say the amount of near-surface and tropospheric warming predicted by even the most conservative of IPCC models has utterly inconsistent with balloon and satellite temperature measurements in the last 23 years
- Some scientists say that solar activity correlates with global atmospheric temperature very well, but that the carbon dioxide level does not.
- Some scientists say that the earth is recovering from a Little Ice Age and that the optimum temperature is what it was when Greenland was green.
Perhaps you agree with the former Clinton Administration that "the science is settled". Perhaps you accept the IPCC's point of view that there is a scientific "consensus". But there are thousands of scientists who disagree. I intend to present their point of view as well.
This article needs a full rewrite, and if I do it, it will take me a dozen hours (maybe much, much more). I would hate to invest this time if anyone would immediately revert the article. I would prefer to be able to make changes boldly[?], but if it will save my time and energy to submit each change for approval I will do it that way.
I want to cooperate. I do not want to slip in changes "hoping" they won't be noticed. On the contrary, I want people to notice my contributions. I might even be able to point out something which a reader had not known before, which contributes to their understanding. Or at least lets them know that someone else has a reason for disagreeing with them.
Ed Poor, Friday, June 14, 2002
Sorry, I?m going to go off on a tangent here (I haven?t yet read what was reverted so I can?t speak to that yet). Who says that the Earth has any sort of temperature optimum? Does this mean that there is an equilibrium point for temperature? All the evidence that I have seen about ?average? surface temperatures is that they have been anything but consistent through recent geologic time - that is until about 10,000 years ago. Before the thawing of the last glacial maximum (we are now in a glacial minimum) the earth periodically experienced very severe climate shifts of +/- 5 degrees Celsius on a more or less 1,500 year cycle (this translates to about a +/- 10 degree C climate change for the poles since they experience the lions-share of warming).
This all appears to have a lot to do with waxing and waning cycles in ocean circulation currents that may be influenced by orbital and/or solar cycles. There is also an increasing amount of evidence that strongly suggests that a prolonged period of warming (most probably caused by increases in [CO2]) may in fact trigger rapid cooling (gulf stream warms Europe, melting fresh water ice shuts down gulf stream and in turn the global circulation of the oceans = tropics get hotter, put more water vapor in the atmosphere and continental glaciation from the poles advance - fed by freezing water vapor). Ice core data have, in fact, found a very strong correlation between CO2 concentration and climate conditions. What is highly unusual, and I mean blatantly weird, however, is the fact that the last 10,000 or so years have been so stable. It is this stability that allowed our Stone Age ancestors to foster civilization and technology (having your population plummet during a climate shift doesn?t do much for establishing civilization). The Medieval Warm Period and the Little Ice Age are nothing compared to geologically recent climate shifts.
My fear is that we are experimenting on the Earth on a global scale by placing known greenhouse gasses in the atmosphere at very high levels. Of course since we don?t have a non-human populated carbon copy control Earth sharing our same orbit we can?t be ?sure? that what we are doing has resulted in the measured and undisputed increase in surface temperature. But when we know (and strongly suspect) certain things about past climate shifts and when we know the thermal properties of certain gases, know that the concentration of these gases have increased very significantly since the start of the industrial revolution and know that the vast majority of the extra concentration of these gases is due to human activity, it doesn?t take a rocket scientist to figure out that we should be concerned. In the blink of a geologic eye we have escaped the clutches of a highly volatile climate system that kept our ancestors in caves. The United States (among a others) are going past the point of looking the gift horse in the mouth - we (and I am American here) are beginning to kick the horse in the groin. How long will it be before the horse kicks back? --maveric149, Friday, June 14, 2002
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