This thread has been opened primarily as a reference section for the benefit of members who haven't posted in the climate forum before. To this end I'd grateful if regular contributors could perhaps give a summary of their position in the debate, and where appropriate provide some reference links.........Thanks in advance
Edited by user 16 June 2010 22:00:54(UTC)
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To start this off, here is a link to Spencer Weart's site
This is a very comprehensive introduction to the Mainstream science and is thus fully representative of my position on the subject.
The links page is also useful
Edited by user 15 June 2010 13:52:02(UTC)
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to try and bring a thread back on topic I'll bring this discussion over here although maybe each of these should have their own thread (depending on how much discussion occurs). IMO two common issues often discussed are that the either CO2 isn't increasing or that the increase isn't anything to do with us. For example,
"Over the past 250 years, humans have added just one part of CO2 in 10,000 to the atmosphere. One volcanic cough can do this in a day."
"The solubility of carbon dioxide in water is listed in the Handbook of Chemistry and Physics as a declining function of temperature. The rising values of atmospheric carbon dioxide during the time of the Mouna Loa measurements could clearly be a function of reduced solubility of CO2 in the oceans of the Planet."
One only needs a tiny reduction in oceanic CO2 absorption to allow a CO2 buildup in the air and of course just such a reduction in uptake does occur when the ocean surfaces are less cold.
Edited by user 17 June 2010 08:34:07(UTC)
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This has been my conclusion, that Manmade Anthro warming is at most only a very small part of recent warming.
June 6th, 2010 by Roy W. Spencer, Ph. D.
One of the main conclusions of the 2007 IPCC report was that the warming over the last 50 years was most likely due to anthropogenic pollution, especially increasing atmospheric CO2 from fossil fuel burning.
But a minority of climate researchers have maintained that some — or even most — of that warming could have been due to natural causes. For instance, the Pacific Decadal Oscillation (PDO) and Atlantic Multi-decadal Oscillation (AMO) are natural modes of climate variability which have similar time scales to warming and cooling periods during the 20th Century. Also, El Nino — which is known to cause global-average warmth — has been more frequent in the last 30 years or so; the Southern Oscillation Index (SOI) is a measure of El Nino and La Nina activity.
A simple way to examine the possibility that these climate cycles might be involved in the warming over the last 50 years in to do a statistical comparison of the yearly temperature variations versus the PDO, AMO, and SOI yearly values. But of course, correlation does not prove causation.
So, what if we use the statistics BEFORE the last 50 years to come up with a model of temperature variability, and then see if that statistical model can “predict” the strong warming over the most recent 50 year period? That would be much more convincing because, if the relationship between temperature and these 3 climate indicies for the first half of the 20th Century just happened to be accidental, we sure wouldn’t expect it to accidentally predict the strong warming which has occurred in the second half of the 20th Century, would we?
Temperature, or Temperature Change Rate? This kind of statistical comparison is usually performed with temperature. But there is greater physical justification for using the temperature change rate, instead of temperature. This is because if natural climate cycles are correlated to the time rate of change of temperature, that means they represent heating or cooling influences, such as changes in global cloud cover (albedo).
Such a relationship, shown in the plot below, would provide a causal link of these natural cycles as forcing mechanisms for temperature change, since the peak forcing then precedes the peak temperature.
Predicting Northern Hemispheric Warming Since 1960 Since most of the recent warming has occurred over the Northern Hemisphere, I chose to use the CRUTem3 yearly record of Northern Hemispheric temperature variations for the period 1900 through 2009. From this record I computed the yearly change rates in temperature. I then linearly regressed these 1-year temperature change rates against the yearly average values of the PDO, AMO, and SOI.
I used the period from 1900 through 1960 for “training” to derive this statistical relationship, then applied it to the period 1961 through 2009 to see how well it predicted the yearly temperature change rates for that 50 year period. Then, to get the model-predicted temperatures, I simply added up the temperature change rates over time.
The result of this exercise in shown in the following plot.
What is rather amazing is that the rate of observed warming of the Northern Hemisphere since the 1970’s matches that which the PDO, AMO, and SOI together predict, based upon those natural cycles’ PREVIOUS relationships to the temperature change rate (prior to 1960).
Again I want to emphasize that my use of the temperature change rate, rather than temperature, as the predicted variable is based upon the expectation that these natural modes of climate variability represent forcing mechanisms — I believe through changes in cloud cover — which then cause a lagged temperature response.
This is powerful evidence that most of the warming that the IPCC has attributed to human activities over the last 50 years could simply be due to natural, internal variability in the climate system. If true, this would also mean that (1) the climate system is much less sensitive to the CO2 content of the atmosphere than the IPCC claims, and (2) future warming from greenhouse gas emissions will be small.
Edited by user 19 June 2010 15:11:14(UTC)
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.The geologic record shows clearly that the sun is the main climate driver. The Milankovitch multi-millennial orbital cycles in NH insolation are firmly established in the record as are the Schwab and deVries cycles. Other millennial and decadal variations in solar activity are present in the record. TSI is not the only or even the best indicator of solar activity – variations in EUV radiation and the GCR flux (via cloud formation and earth’s albedo) seem to be more important on decadal and centennial scales . Earth’s climate is the result of complex resonances between all these solar cycles with the lunar declination cycles and endogenous earth processes.At this time the sun has entered a quiet phase with a dramatic drop in solar magnetic field strength since 2004. This suggests the likelihood of a cooling phase on earth with Solar Cycles 21, 22 ,23 equivalent to Solar Cycles 2,3,4, and the delayed Cycle 24 comparable with Cycle 5 so that a Dalton type minimum is probable.It is now clear that the patterns of the earth’s ocean and atmospheric current systems provide the most immediate guide to the current state of the climate when climate is considered as the result of the complex processes discussed above and these systems provide the best clues as to l developments over the next 20 – 30 years. Beyond that time span predictions are currently of little practical value. The small effect of anthropogenic CO2 cannot be calculated with any useful accuracy until we can better quantify the effect of the natural variations.The IPCC CO2 -anthropogenic warming projections are based on models. AR4 WG1 section 8.6.4 deals with the reliability of the projections.This IPCC science section on models concludes"Moreover it is not yet clear which tests are critical for constraining the future projections,consequently a set of model metrics that might be used to narrow the range of plausible climate change feedbacks and climate sensitivity has yet to be developed"What could be clearer. The IPCC itself says that we dont even know what metrics to put into the models to test their reliability.- ie we don't know what future temperatures will be and we can't calculate the climate sensitivity to CO2.This also begs a further question of what mere assumptions went into the "plausible" models to be tested anyway.Of particular note in climate forecasting is the negative phase of the PDO which began perhaps five years ago and may well last for another 25years. This suggests that La Ninas will be more frequent than El Ninos during this time span. A general earth cooling is thus more likely as was the case from 1940 to 1970 when similar conditions prevailed. Concurrent changes in the Arctic Oscillation suggest a pattern of meridional atmospheric flow will be more common than the more latitudinal flows of warmer periods.Policymakers may wish to note the following possible effects on earth’s climate for the next 20 – 30 years. A cooler world with lower SSTs usually means a dryer world. Thus droughts will be more likely in for example east Africa with possible monsoon failures in India. In California the PDO will mean less rainfall with more forest fires in the south. However in the Cascades and Northern Sierras snowpack could increase since more of the rain could occur as snow. Northern Hemisphere growing seasons will be shorter with occasional early and late frosts and drought in the US corn belt and in Asia repeats of the harsh Mongolian and Chinese winters of 2009 – 10 . In Europe cold snowy winters and cool cloudy summers will be more frequent .There will be a steeper temperature gradient from the tropics to the poles so that violent thunderstorms with associated flooding and tornadoes will be more frequent in the USA, At the same time the jet stream will swing more sharply North – South thus local weather in the Northern hemisphere in particular will be generally more variable with occasional more northerly heat waves and more southerly unusually cold snaps. In the USA hurricanes may strike the east coast with greater frequency in summer and storm related blizzards more common in winter.The southern continents will be generally cooler with more frequent droughts and frost and snowin winter,Arctic and Antarctic sea ice may react differentially to an average global cooling. We might expect sea ice to increase in the Antarctic but in the NH the Arctic Oscillation while bringing cooler temperatures further south may also bring warmer air into the Arctic with possible relative loss of sea ice in that area.The most general advice is that world food production will be subject to occasional serious severe restriction because of cold and drought. The use of food crops for biofuels should be abandoned and stockpiles built up for possible lean times ahead.. Northern cities and transportation systems should prepare for more frequent heavy snow and ice storms.There is no threat from the burning of fossil fuels for the forseeable future, indeed an increase in CO2 would positively help in feeding the burgeoning population.For the next 20 years climate science should be devoted to improving and enlarging the entire climate data base in particular with regard to solar data of all kinds. No climate model runs should be made until 2025 by which time the inputs will hopefully be more relevant to the real world.
a) CO2 is increasing
b) The increase in CO2 is due to the effects on man.
We've discussed this a number of times and each time you state no one disputes those. I think they do and hoped my quick google showed why I think people do dispute a) and/or b). So I'm wondering what evidence has convinced you that a) and b) are correct.
A) it does appear to be, yes.
B) This is probably not as straightforward as some would have us believe, an example: prior to 2001 "Kilauea" a volcanoe in Hawaii was thought to produce 2800 tonnes of Co2 per day, Gerlach and co authors established by measurement a more accurate figure of 8,800 tonnes per day, some 3 times a s much, thats just one volcanoe. We also have absolutely no idea how much Co2 is being produced by underwater Volcanoes. Also "Slocum" 1955 has the average level od Co2 in the last two centuries as 335ppm and i could go on, but my point is there is some doubt as to how much Net Co2 man has contributed to the atmosphere, however it is my opinion that we do contribute about 4% per annum to the natural cycle, but this is not yet 100% in my opinion, it could be more or less.
What is clear is that they need to stop chopping down the Forests.
Edited by user 21 June 2010 13:20:56(UTC)
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Taking a different view about natural variabillity,
Dr Lovell's lecture to the Geological Society (which TomC originally posted) is well worth viewing.
Amongst other issues addressed, it accepts (as have most people since the late 70's early 80's) that the Milankovitch cycles can be used to account for the majority of climate change during the quaternary/ earths history. However, it also points that oribtal eccentricities do not explain the Paleocence-Eocence Thermal Maximum (PETM), where it appears (quite distinctly in the geological record) that CO2 forced temperature, rather than the usual lag (which most sceptics point to in discussions relating to evidence from the geological record).
Dr Lovell contends that the anthropogenic release of carbon that has been locked away from the atmosphere for 10's/ 100's millions of years has put us about 1/3 of the way towards the CO2 peak associated with the PETM. He also gives residence times for the CO2 (i.e. how long it will hang about in the atmosphere before being removed by natural processes).
I have yet to see a coherent rebuttal of this lecture.
A rather nice document from SwissRe addressing the Sceptical arguments.
Having read some of the user friendly doc i especialy take exception to one of the first paragraphs on page 18 where he states that there are no known natural proccesses that could attribute to any recent warming. The author must be on something funny, because that is so not true, it is just a matter of how much no if?
"There is no known natural factor whose recent evolution could explain the recent warming"
Is this the quote you're referring to Robertski? It doesn't include the word 'any'
I would say that natural factors could have come together to cause the recent warming, however, what we know of their recent evolution does not suggest that this is the case. Seems to me that this is why sceptics all seem to have their own pet theory, as they try and dig around for a natural factor that they think would cause the recent warming.
In fact, I have just had the realisation that sceptics occasionally do what they claim 'warmists' do. The claim (often unsubstantiated) is that 'warmists' think all the recent warming is due to CO2. I have come across many sceptics who do exactly this with their pet theory, be it ocean variability, the sun, or some other factor.
Same with the biggest Pet theory of all...AGW.
No,i think the "alarmist" camp has us sceptics wrong. The only "pet" theory we have is the AGW is wrong by some degree. So, most of us would agree that the basic sciense is correct, in theory and such could be contributing to a small,portion of recent warming, however we also believe that most of the recent warming is "Natural". So lets put it this way, maybe the AGW theory is partly correct, but that there is no danger to man via mans input of Co2 into the atmosphere via warming. The objection we have is the amount of fear and guilt being placed on us for what will be a "none" event and we will continue to see the climate ebb and flow until the next Ice Age.(whenever that is)
Edited by user 01 July 2010 15:32:49(UTC)
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No,i think the "alarmist" camp has us sceptics wrong. The only "pet" theory we have is the AGW is wrong by some degree. So, most of us would agree that the basic sciense is correct, in theory and such could be contributing to a small,portion of recent warming, however we also believe that most of the recent warming is "Natural". So lets put it this way, maybe the AGW theory is partly correct, but that there is no danger to man via mans input of Co2 into the atmosphere via warming. The objection we have is the amount of fear and guilt being placed on us for what will be a "none" event and we will continue to the climate ebb and flow until the next Ice Age.(whenever that is)
Anyway, I'm not really thinking of people like yourself but of more public "sceptics". For example, we have the likes of Pier ***** (who thinks it's all solar) and the likes of Ken Ring (who thinks it's all lunar). Although they both agree it's ABCD, I've yet to see either explain why the other is completely wrong. Then there are those who think it's all down to things like El Nino, the PDO, the thermohaline conveyor, etc. Again whilst they'll spend time explaining why it's ABCD there's no mention of why PC and/or KRs ideas are wrong.
It's for reasons like that I see "sceptics" as having a lot less in common with each other than you appear to (other than they agree it's ABCD). For example, whilst you appear to think 1) and 2) are "about right" others don't.
I'll add my pennyworth.....
There are a number of primary drivers of climate, of which solar output, orbital cycles, greenhouse gases, tectonic arrangements of continents and aerosols are all examples. At different times in the geological past, these have all worked in combination with one or more at the fore.
At present we have:
Solar output: pretty much steady
Orbital cycles: interglacial, as indeed we have
Greenhouse gases: substantially increased to pre-Quaternary levels
Tectonics: essentially unchanged for thousands of years
Aerosols: decreased in recent decades compared to e.g. 1940s
On a smaller cyclic scale we have e.g. the 11-year solar cycle - emerging from a minimum - and ENSO - transitioning from El Nino to La Nina. Clearly both can cause minor fluctuations, but the 1970s-2000s signal that emerges from the noise they produce (e.g. the 1998 temperature spike) is a gradual warming trend.
Outside the average temperature record, examples of other evidence for a warming trend are:
Continuing substantial summer melt in the Arctic
Poleward migration of land & sea species
Record heatwaves - one in Russia this year for example
Increase in extreme precipitation events - USA Midwest, Pakistan etc
It is my view that we are heading back to a pre-Quaternary climate, whatever we do now.
The real risk is that we further destabilise the situation, so that we end up heading for a climate not seen since the Oligocene or even the Eocene. That might take a few centuries to bring about, but it will involve total land ice loss and ~60m of sea level rise.
At the same time, we are close to the peaking in regular oil supplies, and coal and natural gas will only keep us going for another 150 years or so, at the present rate of consumption.
Fossil fuel usage as a prime energy source means that we are at the mercy of other nations from whom we import them, which is fine so long as we get on. Unfortunately we do not all of the time.
Transitioning from fossil fuel dependency to renewables whilst at the same time reducing demand via efficiency/lifestyle changes will reduce the rate of accumulation of greenhouse gases and will in addition remove that dependency on other nations: furthermore it will mean that we are ready to leave oil before it leaves us once the supply starts its inevitable decline. Not being ready for the latter will have far-reaching consequences, and not of a pleasant nature.
Two huge problems and one single, but difficult, solution. Can we do it?
Cheers - John
Your summary is completely over the top, the Arctic Ice pack is recovering albeit slowly. Antacrtic Ice is and has been well above "normal". We have had one the coldest Southern hemisphere winters in the Southern Hemisphere for about 40 years. The Arctic has just had one of its coldest recorded Summers. The West coast of the United States has also been very cold. There is far too much nonsense being made of the heat in Russia which has got to do with our current unusual weather pattern and nothing to do with any AGW. Your post sums up nicely the one sided bias that is being put out by the media. Over 400 people dying in Southern hemisphere cold and large areas losing masses of wild life to the cold and not one report on the television that i know of.
Edited by user 16 August 2010 10:47:11(UTC)
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