[chris (OP)]

I received this email from a podcast listener today:

To: thenakedscientists@yahoo.com
Date: Sunday, 7 December, 2008, 10:27 PM

I like your show and listen to it via podcast. I have to say though that I take your scientific information with a grain of salt. The reason? Your apparent acceptance of man made global warming. As scientists, I just don't understand how you can accept it. There is no proven cause and effect of carbon dioxide and warming, let alone that the relatively small amount of carbon dioxide made by man is enough to affect the atmosphere. The computer models which "prove" MMGW aren't science - they aren't proof and they haven't even predicted future events. I've read that warming stopped around 1998 and the Earth has actually cooled for the last couple of years.

One would think that the Sun would have much more to do with long term climate changes than anything man does.

I feel that your show is "politically correct" and therefore I always wonder if what you say is true science or not.

Oh, you also say "aluminum" funny.


I sent the following reply, but I would be grateful for the thoughts of other forum users:

Dear DT

thank you for writing. I'm delighted that you like our show and that you choose to listen to us on a regular basis.

In answer to the point you raise about the trustworthiness of our content, please ask yourself whether a group of highly qualified people, who are funded by two of the world's most important independent research councils (The Wellcome Trust and the EPSRC) and based at one of the world's top universities (Cambridge) would dare to risk their scientific reputations and credibility by airing content that was not scientifically sound.

We base our output only on peer-reviewed material published in high-impact scientific journals. I'm not sure where you are obtaining your data about global temperatures, but it certainly doesn't seem to be consistent with what is appearing in the recent editions of Nature and Science. Perhaps some of the other sources that you have been reading or listening to are a little out of date?

Regarding the impact of humans on the environment, that we are able to impact the planet and the ecosystem on a global scale is without question. The hole in the ozone layer, discovered in 1985-6 by BAS researchers, was principally due to man-made release of halogenated refrigerant and propellant molecules.

I acknowledge that the ozone hole should not be confused with global warming (although global warming may make the process worse), but this serves as an example that seemingly "trivial" emissions of invisible gases can have major worldwide impacts.

Where CO2 is concerned, the anthropogenic (man-made) CO2 release per year is about 30 billion tonnes. Contrast this with global volcanic emissions of greenhouse gases, estimated to be about 100 million tonnes. This means that humans produce a whole order of magnitude more CO2 than volcanoes, which (history has shown) have powerful and demonstrable impacts on climate and global temperatures.

Therefore it is not unreasonable to assume that there are likely to be climate consequences of these emissions.

The more pressing question is can we afford to wait (and do nothing) in order to find out?

Best wishes

Chris Smith, The Naked Scientists.

[paul.fr]

In advance, I apologise for a fragmented reply.

For various reasons this is one topic I have stopped participating on, on the forum, but I would like to say that science, scientists and governments only have themselves to blame for the arguments and confusion.

The emailer is right to call in to doubt the accuracy of the climate models, they are made by programmers, not climatologists and even the IPCC think their present model is wrong, and they don't fully know how feedback loops of atmospheric water will work.

would dare to risk their scientific reputations and credibility by airing content that was not scientifically sound.

A good argument could be made that, going along with the consensus is the only way to get funding, get published and be recognised in the field. Trying to go against the IPCC and the so called "Gore lobby" can be career and social suicide.

The emailer is also correct when he (?) say the earth is cooling, albeit, ever so slightly. It is also possible that we are in the 10th of a 30 year period of average stasis or decline in global temperatures. Another good argument against global warming, which is we we now use the term "climate change".

The more pressing question is can we afford to wait (and do nothing) in order to find out?

But that is what we are doing, no amount of data or warning presented have really changed how governments act, they merely provide lip service to the green lobby or to convey their green credentials to a gullible and illinformed public.

[dentstudent]

The emailer is right to call in to doubt the accuracy of the climate models, they are made by programmers, not climatologists and even the IPCC think their present model is wrong, and they don't fully know how feedback loops of atmospheric water will work.

This is not entirely true. Climatologists invariably have to be modellers – in many sciences, there is an overlap because it is a part of the process to describe and forecast what is going to happen. Modelling is an integral part of predictive science, and therefore the models are (often) created by those scientists who are making the scientific evaluations. You do not have to be a “programmer” to create a model – there are many systems that are in place through which predictive models can be built, for example SAS, SPSS, R and so on. In my field of natural regeneration of trees, I have made many models using SAS, but I would not call myself a programmer. I have links with the climate change institute in Potsdam (PIK) – this same situation applies. There are many scientists working with climate information who then model various scenarios – they would call themselves climatologists, and not programmers. There are certainly specialists in each field, so there will be individuals who are specialist climate modellers, but they absolutely must have a complete understanding of climate processes in order to create the model. The data is not outsourced from scientists to “programmers” – the models are in-house and extensively tested. It is true that the IPCC believe that some information is incorrect. Firstly, this is based on not just one model, but more than 20 different models, each assessing various aspects of CC. There are also a series of scenarios against which various political statements are made. An example of this is the breaking up of the northern ice cap. It wasn’t so long ago that it was predicted to be clear in the summer within 100 years or so. Now, the figure is being revised down, to perhaps as little as 30 years. The problem is that the earth is an incredibly complex system, and models can only capture a small part of each system. Therefore, it is not surprising that revised figures are often broadcast. This does have the effect that when put through the media, it appears that climatologists don’t appear to know what is going on. But as CC is such focal issue, there is a demand for information. The truth is that no-one really knows what will happen, since there are so many tipping points and critical values that may or may not be experienced. Hence there can only ever be a broad overview of the likely CC outcomes.

A good argument could be made that, going along with the consensus is the only way to get funding, get published and be recognised in the field. Trying to go against the IPCC and the so called "Gore lobby" can be career and social suicide.

An argument could be made, but whether it is a good one or not perhaps depends on your view as to whether it is some sort of conspiracy. How is this different to say, funding provisions in the ‘60’s for space exploration? There was (is) a demand for scientific evaluation – why should this not be done?

The emailer is also correct when he (?) say the earth is cooling, albeit, ever so slightly.

Really?

But that is what we are doing, no amount of data or warning presented have really changed how governments act, they merely provide lip service to the green lobby or to convey their green credentials to a gullible and illinformed public.

I disagree – the political system does take a long time to adopt and adjust, but there are certainly changes that have taken place as a result of desires to reduce C emissions.

[paul.fr]

Stuart, what I posted were the arguments of people who are not informed, those that rely on the media, the guy in the pub or average joes opinion on the internet.

It is quite easy to see where and why people get confused. The present predictions are so far from the initial ones, of the whole world freezing, and spawning disaster movies to show us what to expect. People still use the term global warming, when introducing a piece about how certain areas will actually cool. The IPCC release their predictions and then state that they actually think it will be a lot worse that their models predict, it just leads to confusion, followed by more confusion.

You have authorative figures, such as clergy, telling you two different tals. they are not climatologists but their opinion is taken because of their position in the community.

There are researchers who do find funding for the case against CC hard, and are vocal about that.

What i do believe is true, is, that the government only pay lipservice to the issue. It is obvious that we need to be building nuclear power stations but where are they? Well, we are still debating them. The gov. promised to stop inporting rare timbers to help sustain the rain forest, but clad offices in the house with rare timber. What are the public to make of this?

What they will do is simply keep saying the right things and leave the big headache, paying for it, to the next lot. The latest target for emissions (yet to be agreed) is to get back to 1990 levels by 2020. Can we do that? and does it go far enough? If this is the best we can hope for then we are doomed, doomed i tell y'.

[dentstudent]

I think that the "people to blame" in this situation (since it is apparently a blame society, which rather sickens me TBH, rather than it being an accountable society) are the media (by which I mean all forms of media other than this well-informed site!). There really is no debate within the scientific arena about CC (I don't know of any scientists who call it global warming). There are perhaps 2 or 3% who are denying it, but there is always this group whatever the cause. My beef, as I say, is with the media who think that they are putting an even and well-balanced arguement when discussing what they consider to be both sides of the CC arguement, when infact there is no strong anti-CC lobby. I agree that it is a difficult topic, and that information changes often, but what generally happens is that Britain gets ooh, 5 cm of snow, and then people start discussing "where has CC gone?" rather than looking at the bigger picture.

But, even if there are targets, what are they based on? Why 1990 levels by 2020? I think that instead of necessarily trying to set targets, time could be better spent developing methods of paying for scrubbers etc for new eastern CF power-stations.

So let's post well-informed and well supported items, and show that irrespective of whether it is anthropogenic or not, atmospheric C is increasing, the consequences of which can be seen to create a trend towards highly volatile climate scenarios, which are increasingly difficult to predict (and model) as a direct result of their inherent volatility. There is an overwhelming body of evidence that shows that changes are at hand, and that these changes will have profound effects on our environment.

A final note: Ironically, from even within at least my scientific domain, it is now increasingly difficult to get funding for pure CC research.

[dentstudent]

Here are some IPCC documents

[DoctorBeaver]

I agree with what has been said about the media. I think part of the reason is that, in the interest of fairness, every time someone is interviewed who believes in CC, another is interviewed who doesn't. This gives the impression that scientists are split almost 50/50 on the issue.

[frethack]

There really is no debate within the scientific arena about CC (I don't know of any scientists who call it global warming). There are perhaps 2 or 3% who are denying it, but there is always this group whatever the cause.

I am not entirely sure how to interpret what you have said here, dentstudent, so if I am being repetitive (or contradictory  [] ), I mean it in a respectful tone.  As youve stated, I dont know any scientists who still call it "global warming", and I dont know anyone who denies that the climate is changing (though Im sure theyre out there...I hear about them all the time).  There is, however, debate in the climate community about anthropogenic induced change as opposed to natural cyclicity, and the degree to which each is affecting global climate. 

[techmind]

The daily weather forecast is often wrong in the details, but this doesn't mean that the overall method of weather-forecasting is complete bunkum. Ditto for climate models.

My interpretation (I don't claim a special interest or knowledge of climate-science):

The climate is incredibly complex, with not all aspects fully understood. Any model will involve some simplifications and fudges for unknowns (or partial unknowns), but that still does not detract from the basic premise that man-made CO2 (and other gas) emissions are highly likely to lead to CC.
We can make a pretty good estimate of how much fossil fuels are burnt annually, and therefore how much additional CO2 human activity is putting into the atmosphere. We also have records of atmospheric CO2. Underlying principles such as greenhouse effect can be gauged and tested from first principles by measuring spectral absorbtion etc of potential greenhouse gasses. From this we can infer that climate change should be taken seriously. The (more detailed, but also more uncertain) climate models help to narrow down the likely timescales and degree of warming, although more fundamental physics assures us that there will be issues of some sort, at some point.

[frethack]

The daily weather forecast is often wrong in the details, but this doesn't mean that the overall method of weather-forecasting is complete bunkum. Ditto for climate models.

You are correct that climate models do have their purpose and do aid in very short term climate forecasting, but until we can understand important processes such as cloud formation or how the atmosphere vents heat to space, the models will always be very inaccurate. (there are many others...these are only two)

This article is over a postulated Pacific atmospheric heat vent.  Ill see if I can find a free link to the journal article from the Bulletin of the American Meteorological Society.  This article is a NASA release from 2001, but I have not seen any other work on Pacific ocean energy vents.
http://earthobservatory.nasa.gov/Newsroom/view.php?id=21464

Im sure that this has been posted before, but Ill post it again anyway.  It is work by Svensmark and Marsh on a connection between cosmic radiation flux and cloud nucleation.  This paper is from the Proceedings of the Royal Society A.  Another experiment is set for 2010 at the CERN reactor.
http://journals.royalsociety.org/content/3163g817166673g7/

[dentstudent]

There really is no debate within the scientific arena about CC (I don't know of any scientists who call it global warming). There are perhaps 2 or 3% who are denying it, but there is always this group whatever the cause.

I am not entirely sure how to interpret what you have said here, dentstudent, so if I am being repetitive (or contradictory  [] ), I mean it in a respectful tone.  As youve stated, I dont know any scientists who still call it "global warming", and I dont know anyone who denies that the climate is changing (though Im sure theyre out there...I hear about them all the time).  There is, however, debate in the climate community about anthropogenic induced change as opposed to natural cyclicity, and the degree to which each is affecting global climate. 

Hi Frethack - thanks for your comments!

Here is some information from PIK (The Potsdam Institute for Climate Change Research) concerning CC. (The English is sometimes slighty off as it's a translation)


1. Burning fossil fuels, deforestation and other human activities have released large amounts of greenhouse gases. The concentration of carbon dioxide in the air has risen from the pre-industrial level of 280 parts per million (0.028 percent, ppm means “parts per million”) to more than 380 ppm today. That is the highest level since at least 800,000 years and is forcing a massive anthropogenic, “human made”, greenhouse effect on Earth. Global mean temperature has already risen by about 0.8 degrees Celsius (1.5 degrees Fahrenheit) since 1900.

2. If business continues as usual, the world could heat up by about five degrees Celsius (nine degrees Fahrenheit) by 2100. This is roughly the temperature difference between an ice age and a planetary warm phase. Since Earth’s climate is currently in a warm phase humanity would thereby create a “fire age”.

3. Global warming leads to the thermal expansion of sea water and increases melt-water runoff from glaciers and ice sheets. Sea level has risen by about 15 to 20 centimetres during last century; another 50 to 150 centimetres are expected this century. Continued warming could destabilize the Greenland and Antarctic ice sheets. In Earth’s history sea level rose by 10 to 15 metres with each degree of global warming. It is not yet clear though, how much time that process took.

4. The anthropogenic greenhouse effect could push the Earth’s climate system past critical thresholds, so that important components may “tip” into qualitatively different modes of operation. This would affect climate on a sub-continental scale and could cause the complete disappearance of Arctic sea-ice and Himalayan glaciers or large-scale dieback of the Amazon rainforest. If the climate system started to release greenhouse gases, positive feedbacks could lead to runaway greenhouse dynamics.

5. According to current knowledge, the most dangerous impacts of climate change could be averted, if anthropogenic warming was limited to two degrees Celsius (3.6 degrees Fahrenheit). This requires confining the concentrations of all greenhouse gases and their effect to a level that does not exceed that of 450 ppm carbon dioxide. To reach the two degrees target, global emissions of greenhouse gases have to be reduced by 2050 to about half of the level of 1990.

6. If the potential for technological and institutional innovation were fully tapped, the measures implicated by the two degrees target would reduce global economic output by about one percent until 2100. Given a mean global economic growth of three percent, the delay would be offset in about four months.

7. Adaptation to climate change and the confinement of global warming to two degrees Celsius require a “Great Transformation” of the global economy and of urban and rural life.

PIK - climate-change-knowledge-in-a-nutshell

PIK are involved in the IPCC - it seems clear to me that they consider there to be an anthropogenic effect, and that there is no disagreement within at least this scientific institute.

[dentstudent]

PIK - Potential Anthropogenic Tipping Elements in the Earth System



1 Arctic Sea Ice Loss

As sea ice melts in a warming climate, it exposes a dark ocean surface, which absorbs more solar radiation and thus amplifies the warming. Over the last 30 years the area covered by sea ice has decreased significantly. This is also bad news for many species, like seals or polar bears, which depend on that ice for hunting and breeding. Time Frame: ~ 100 yr.
 
2 Melting of Greenland Ice Sheet

Greenland’s ice sheet is melting due to the extraordinary warming of the Arctic region. Recent observations suggest an accelerated destabilization also due to melt-water lubrication effects. The complete collapse of the Greenland ice sheet would cause a global sea level rise of 7 m. Time Frame: Unknown due to highly non-linear processes. Current estimates: 300–1000 yr.
 
 
3 Methane Escape from Thawing Permafrost Regions and Continental Shelves

Huge amounts of methane, which is a highly potent greenhouse gas, could be released by climate change. On the one hand, terrestric methane will emanate from thawing permafrost areas in Siberia and Northern America. On the other hand, ‘methane ice’ assembled by natural processes over millions of years off many coasts might be activated by changing ocean temperatures and currents. Time Frame: ~ 1000 yr.
 
4 Boreal Forest Dieback

Northern boreal forests account for almost one third of the global forest inventory. They are declining in a warming climate because of enhanced disturbance stress through fires, pests, and storms. At the same time, their regenerative capabilities are diminished by temperature and water stress as well as direct human interference (logging, fragmentation, etc.). The dieback would trigger massive release of carbon dioxide, which in turn enhances climate change as well as significant losses in biodiversity. Time Frame: ~ 50–100 yr.
 
5 Suppression of Atlantic Deep Water Formation

The warm Atlantic surface ocean current is responsible for the benign climate in Northwestern Europe. This gre- at ‘conveyor belt’ is ultimately driven by cold and dense water sinking to the bottom of the North Atlantic off the coasts of Greenland and Labrador. A warming climate leads to an increased freshwater flow into the ocean, thus decreasing the water’s density and slowing down the deep water formation. Time frame: ~ 100–500 yr.
 
6 Climatic Change-Induced Ozone Hole over  Northern Europe

Particularly Northern Europe could face a climate change-induced ozone hole. Climate change at the bottom of atmospheric strata implies cooling in the stratospheric “roof”. This cooling induces ice cloud formation which in turn provides a catalyst for ozone destruction. Time Frame: ~ 10–1000 yr.
 
7 Darkening of the Tibetan Plateau

As the snow cover of the Tibetan territory melts due to climate change, the exposed dark rock surface will amplify regional warming through increased absorption of solar radiation. As a side effect, the freshwater supply for many Asian countries, which depend on glacier melt water, will be reduced. Moreover, it is possible that the darkening of the Tibetan plateau could affect the Indian monsoon system. Time Frame: ~ 50–100 yr.
 
8 Disruption of Indian Monsoon

Up to 90% of India’s precipitation is provided by the regular summer monsoon. Carbon dioxide as well as aerosols play a key role in this highly variable system. Air pollution, land-cover change and greenhouse gas emissions could bring about a roller-coaster succession of intensified and weakened monsoons in South Asia causing extreme droughts and floods. Time Frame: 30–100 yr.
 
9 Re-Greening of the Sahara and Sealing of Dust Sources

Vegetation could re-appear due to higher precipitation in the Sahel region, but this greening of the Sahara may be overridden by intensive land-use, especially grazing. If the re-greening happened, it could seal major sources of dust that is blown across the Atlantic and fertilizes South American ecosystems. Time Frame: ~ 50 yr.

 
10 West African Monsoon Shift

The West African monsoon is affected both by heavy deforestation in coastal areas and increasing sea-surface temperatures. The future of this monsoon system is still uncertain. Climate change may bring about a doubling of dry years in the Sahel by the end of the century or a complete monsoon collapse, both of which would have profound large-scale impacts. Time Frame: ~ 50–100 yr.
 
11 Dieback of Amazon Rainforest

A large fraction of precipitation in the Amazon basin is recycled evaporation water. The reduction of regional rainfall in a warming climate, intimately connected to El Niño/Southern Oscillation, as well as forest fragmentation due to human activity could bring the forest cover to a critical threshold. Amazon dieback would have profound influence on the global climate and at the same time result in a huge loss of biodiversity. Time Frame: ~ 50–100 yr.
 
12 Change in Southern Pacific Climate Oscillation

Although uncertainties are large, some climate models predict an increased frequency and/or intensity of El Niño conditions in the Southern Pacific. The impacts of such a change in the oceanic oscillation patterns would be felt around the globe, especially in the form of droughts in South-East Asia and many other regions. Time Frame: Rapid changes possible in 10-100 yr.
 
13 Disruption of Marine Carbon Pump

This “pump” acts as a sink for both natural and anthropogenic excess CO2. There is a risk of a decline of this sink caused by increased ocean acidification and stratification owing to rising atmospheric CO2 levels. The acidification impedes floating and fixed organisms, such as plankton algae and corals, to build their skeletons, which bind carbon. Time Frame: unknown.
 
14 Suppression of Antarctic Deep Water Formation and Nutrients Upwelling

Similar to the North Atlantic, convection of water masses in the Southern ocean can be suppressed by freshwater inflow from melting ice. If there is a critical threshold, it has not been assessed so far. The resulting decline of nutrients would reduce krill, which marks the basis of the marine food chain. Time Frame: ~ 100 yr?
 
15 Collapse of the West Antarctic Ice Sheet

Although assumed to be not as vulnerable as the Green- land Ice Sheet, a collapse of the West Antarctic Ice Sheet could be initiated within this century. Warming oceans result in melting of offshore ice shelves, which currently impede the out-flow of the continental ice masses be- hind. Furthermore, the warm water could be undercutting the ice sheet and yield further separation from the bedrock, thus accelerating the decay. The complete ice sheet collapse would raise the global sea level by 4-5 m. Time frame: ~ 300–1000 yr.
 
16 Antarctic Ozone Hole

Already strongly perturbed by humanity’s emissions of chlorofluorocarbons in the past, the protective ozone layer is believed to be regenerating after these chemicals have been banned. Yet strong interactions between stratospheric ozone depletion and climate change may widen the ozone hole over the Antarctic once again. Time Frame: ~ 10–100 yr.

[frethack]

As youve stated, the PIK is in close association with the IPCC, and does not disagree with their assessment.  In fact, by what you have posted here, I would say that they go even farther on some issues.  That does not mean, however, that there is no dissent in the scientific community.  There is a very healthy discourse between researchers concerning climate change within my own university, which is among the most respected schools in geosciences, as well as other very highly respected universities such as Stanford, Caltech, and MIT.

Admittedly I am only just a third year geoscience student with a focus on paleoclimatology, and my pool of information is most assuredly not that of a think tank such as the PIK (nor of many on this forum), but when considering the geologic record, some of the points from the PIK seem inaccurate. 

I have finals this week and then am heading out of town, so I do not have time to post point by point. I will post more next week if the topic is still alive.  Sorry to be vague...gotta keep the GPA up!

[dentstudent]

As youve stated, the PIK is in close association with the IPCC, and does not disagree with their assessment.

It's the other way around - scientists at PIK advise the IPCC on CC, and so would not disagree!

In fact, by what you have posted here, I would say that they go even farther on some issues.  That does not mean, however, that there is no dissent in the scientific community.  There is a very healthy discourse between researchers concerning climate change within my own university, which is among the most respected schools in geosciences, as well as other very highly respected universities such as Stanford, Caltech, and MIT.

A healthy discourse is fine, and is what keeps science active and open-minded. I don't see how the effect of anthropogenic C emissions can be considered inconsequencial in CC, because it is measureable as is the effect.

Admittedly I am only just a third year geoscience student with a focus on paleoclimatology

(this should have no effect on people's consideration of your arguement - it is the evidence that counts, not who is putting it forwards)

, and my pool of information is most assuredly not that of a think tank such as the PIK (nor of many on this forum), but when considering the geologic record, some of the points from the PIK seem inaccurate. 

Let me know which ones, ok?

I have finals this week and then am heading out of town, so I do not have time to post point by point. I will post more next week if the topic is still alive.  Sorry to be vague...gotta keep the GPA up!

Dig out the topic again when you are ready. Good luck with the finals!

[DoctorBeaver]

Yes, good luck.

[paul.fr]

If we go back to the original question: "What is the evidence for global warming?" then the easy answer is there is none, there will not be global warming, there will be climate change.

This is when such topics go in all sorts of directions, possibly my fault here, but i wanted to try and approach this from "the other side" and put forward ideas and "evidence" to support the anti climate change opinion, but i realised i simply don't have the time, but the waters are muddied and there are a few posts that do go off in different directions.

For starters, Chris mentions the ozone hole in the same sentence as global warming, yes he says they should not be confused with eachother but "the damage is done". Many people can not tell the two apart, and think that they go hand in hand...something to be avoided.

It has also been mentioned that the problem with the general publics understanding and confusion may be down to the media, and their efforts to appear balanced and fair, be allowing both side of the argument to be heard. Actually, this is needed, people need to see and hear from both side, how else are they to make their own informed decision? We also need the doubters and sceptics "to keep it real".

Saying that, I do blame the media for sensational headlines and stupid graphics. What I would like to see are a series of lecture's (like the RI Christmas ones) aired on the BBC and have both side state their case, evidence, and facts. It is simply no good leaving people to find the answers from google, the guy in the pub or, dare i say it, internet forums.

What we have is a language problem, especially when it comes to global warming. as has been stated, this is more often than not used in the negative.."do you know why it's so cold", "global warming". It's not just the public that say this, I know meteorologists (weather presenters), research meteorologists and climatologists that use the phrase "global warming" for this purpose. Admittedly it can be funny, even when you know it's coming, but it is used in the negative.

You then have people that insist we can not know the future and using computer models is a joke, heck they can't even get today's weather forecast right! But they are two different disciplines and fields, but they are mistakenly used together as evidence to contradict the science.

As Frethack has said, the main debate now is over climate change being a cyclic event that naturally occurs or whether man made anthropogenic warming is the cause. But this is not what gets back to or is digested by the public, as far as they are concerned its either global warming or its not.

Ahhhh, this takes too long, another reason I hate this type of topic.

[dentstudent]

If there is confusion, then the very least we can do is post information that is as accurate as possible, as up to date as possible, is supported by as much evidence as possible, and that shows the full picture. I agree that in general the public are ill-informed. This is a public forum. Let's use it to convey well researched and critical analyses to reduce this obfuscation.

If CC is going to be debated, then we need to estabish a base upon which it can be set. If it is agreed that the IPCC is the last word in CC, then let's use this. If it's not agreed, then it's likely that I for one am not going to be involved in any discussion. There is no other body that has investigated in such detail over such a long period these climate effects. It is represented by 100's of scientists worldwide who have worked independently and without agenda to provide this information. If there is a feeling that the IPCC is somehow a conspiracy, then I would not be willing to spend time debating anyone with this belief.

In the IPCC report of 2007 an overview is provided that synthesises CC detection results. I would invite anyone interested to read through the document, but all that I am going to post are some of the items from pps 729 - 732. I have somewhat reduced the text, but all the information is there. There is a link to the glossary of terms at the bottom.


Surface temperature

Warming during the past half century cannot be explained without external radiative forcing
Global
Extremely likely (>95%)

Warming during the past half century is not solely due to known natural causes
Global
Very Likely

Greenhouse gas forcing has been the dominant cause of the observed global warming over the last 50 years.
Global
Very likely

Increases in greenhouse gas concentrations alone would have caused more warming than observed over the last 50 years because volcanic and anthropogenic aerosols have offset some warming that would otherwise have taken place.
Global
Likely

There has been a substantial anthropogenic contribution to surface temperature increases in every continent except Antarctica since the middle of the 20th century
Africa, Asia, Australia, Europe, North America and South America
Likely

Early 20th-century warming is due in part to external forcing.
Global
Very Likely

Pre-industrial temperatures were influenced by natural external forcing (period studied is past 7 centuries)
NH (mostly extratropics)
Very Likely

Temperature extremes have changed due to anthropogenic forcing
NH land areas and Australia combined.
Likely

Free atmosphere changes
Tropopause height increases are detectable and attributable to anthropogenic forcing (latter half of the 20th century)
Global Likely

Tropospheric warming is detectable and attributable to anthropogenic forcing (latter half of the 20th century)
Global Likely

Simultaneous tropospheric warming and stratospheric cooling due to the influence of anthropogenic forcing
has been observed (latter half of the 20th century)
Global Very Likely


Ocean changes

Anthropogenic forcing has warmed the upper several hundred metres of the ocean during the latter half of
the 20th century
Global (but with limited sampling in some regions)
Likely

Anthropogenic forcing contributed to sea level rise during the latter half 20th century
Global Very likely

Circulation
Sea level pressure shows a detectable anthropogenic signature during the latter half of the 20th century
Global Likely

Anthropogenic forcing contributed to the increase in frequency of the most intense tropical cyclones since
the 1970s
Tropical regions
More likely than not (>50%)

Precipitation, Drought, Runoff

Volcanic forcing influences total rainfall
Global land areas
More likely than not (>50%)

Increases in heavy rainfall are consistent with anthropogenic forcing during latter half 20th century
Global land areas
(limited sampling)
More likely than not (>50%)

Increased risk of drought due to anthropogenic forcing during latter half 20th century
Global land areas
More likely than not (>50%)

Cryosphere
Anthropogenic forcing has contributed to reductions in NH sea ice extent during the latter half of the 20th
century
Arctic Likely

Anthropogenic forcing has contributed to widespread glacier retreat during the 20th century
Global Likely


Glossary


So please tell me where it is not at least more likely than not that there is an anthropogenic effect on global climate systems.

[Madidus_Scientia]

Oh, you also say "aluminum" funny.

He spells it funny. Maybe that's why he thinks its being said funny. Is the writer American? Why do they often seem to mispronounce things like aluminium and nuclear? Even George Bush pronounces it "Nuke-you-lar".

[paul.fr]

Stuart, if I were an arse a sceptic, I would point out that all IPCC reports are full of words like, may, could, possibly and likely. But i'm not, so i will not say it.

Also have you noticed one of the worlds biggest social network site insists on calling it global warming?

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[dentstudent]

Stuart, if I were an arse a sceptic, I would point out that all IPCC reports are full of words like, may, could, possibly and likely. But i'm not, so i will not say it.

Well, it's a good job we know our science, and know that science only ever provides a probability of something happening, its statistical significance or likelihood. There will never be a scientific journal anywhere that says anything about the "proof", only "disproof".