Global Warming

[parmenides3]

Do, please, read the attachment I posted above from the ACIA; it covers most of what you are asking about.

As far as the estimates are concerned, if a 'scientist' doesn't have the evidence to support his hypothesis/conclusion, his work is unlikely to be published by his peers, in the science journals. If the estimate has not come from a serious (peer reviewed) source, it can normally be dismissed.

Most climate scientists (this'll get their backs up) would probably go with one of the IPCC TAR estimates on sea level rise or temperature change, or an estimate based on one of the known and tested models, like HADCM3, or the CCCM. Some scientists argue AGW, some are on the fence. As of yet, and I am looking, I haven't found a scientist who has denied GW and had his/her work generally accepted as valid by the community.

Finally, I would ask that you read the source naterial (much of which, in the form of academic papers, is on the internet), and reach your own conclusions. If you find a convincing scientific case for saying the world is not really going to get much warmer over the next hundred years at least, please post it; I, for one, will read it avidly. :}

[Anti-Mild]

Do, please, read the attachment I posted above from the ACIA; it covers most of what you are asking about.

As far as the estimates are concerned, if a 'scientist' doesn't have the evidence to support his hypothesis/conclusion, his work is unlikely to be published by his peers, in the science journals. If the estimate has not come from a serious (peer reviewed) source, it can normally be dismissed.

Most climate scientists (this'll get their backs up) would probably go with one of the IPCC TAR estimates on sea level rise or temperature change, or an estimate based on one of the known and tested models, like HADCM3, or the CCCM. Some scientists argue AGW, some are on the fence. As of yet, and I am looking, I haven't found a scientist who has denied GW and had his/her work generally accepted as valid by the community.

Finally, I would ask that you read the source naterial (much of which, in the form of academic papers, is on the internet), and reach your own conclusions. If you find a convincing scientific case for saying the world is not really going to get much warmer over the next hundred years at least, please post it; I, for one, will read it avidly. :}

I had a quick scan of the link and I couldn't help but notice that it was littered with 'could's' and 'may' and 'might' and 'it is possible that', which illustrates the point that should be obvious to everyone and that is as difficult as it is to forecast a week in advance there is no way that 100 years can be forecasted to any reliable degree. Sure there is the hockey stick graph and the rises in CO2 but there is also sunspot cycles and synoptics and possible NAD disruption, etc.

I am not anti-AGW, I would have to be a fool to be, but similarly only a fool would swallow some of the propaganda (from both sides of the fence) because at the end of the day most of it is guesswork, and the arrogance of some climatologists who presume that they can definitively say what the future holds re. GW can be astounding.

[BLAST FROM THE PAST]

Interesting read the other day, latest scientific research [by one of their own] states that IPCC have highly overestimated their claim of projected warming during the 21st century. It suggests now that up to 3C-5C is the likely outcome? Well if you ask me that is still ludicrous, however it does show a big reel in from 8C! My money is on the research now well underway, and with BIG BUCKS, into the solar cycles and influence which will bring this projection down even further...I think we'll see a 0.8c reduction by then The Gleissberg minima is being scoffed on by certain sections but with ACRIMM recording that DOUBLING CO2 at present day levels would have a 0.1% irradiance increase equivalent

, which is about 0.2C, and with the Gleissberg minima likely to be in the range of 0.3 to 0.5% irradiance decrease then on that basis a 0.6 to 1C temp reduction is projected IMO.

BFTP

Edited August 3, 2006 by BLAST FROM THE PAST

[parmenides3]

ACIA references 500 scientists (not just climatologists) and several hundred reference works. Do they all have an agenda? Is it a conspiracy? Or have they published what they found? How many scientists will it take to satisfy your demand for evidence? What is ACIA's 'agenda'? (All asked in the nicest possible way) The section also contains a great many 'probable' and 'very probable' findings; these are statistically significant probabilities of future occurence, not hedging.

And BFTP; all I'll say on this, which we've already discussed, is that there is no evidence of a change on Solar irradiance in the last 50 years, or that sunspots effect our climate; this is much more hypothetical than AGW as things stand. Please give the Graps link: I couldn't find the article on his site.

I read that the next lot of Hadley data to go into the 2007 FAR is likely to re-evaluate the temperature change upward. Do you know anyone at Hadley who could confirm/deny either of our bits of hearsay?

[Thundery wintry showers]

I thought the last IPCC report said a warming of 1.4-5.8C was "likely".

[BLAST FROM THE PAST]

Permanides, I gave the site, will have to look it up again AGW? That to me is hypothetical Well this seems to be the problem, NASA have reported that activity/irradiance has increased 0.05% per decade since 1970

BFTP

I thought the last IPCC report said a warming of 1.4-5.8C was "likely".

TWS

Yes that is the revised thinking, Jan this year is it?

BFTP

Edited August 3, 2006 by BLAST FROM THE PAST

[Thundery wintry showers]

Which report gave higher estimates? The 1.4-5.8C is straight from the 2001 report.

[parmenides3]

BFTP, you'll be pleased to know that I have found at least one reputable scientist who has a lot to say on this subject and appears to favour your ideas (though not necessarily your reasons) over the mainstream CO2 forcing lobby; Roger A. Pielke Sr. He runs the Colorado State climate thingy, and seems to be highly respected. He isn't a GW skeptic, as some have labelled him, but he argues extensively about the need to take other forcing mechanisms, especially solar irradiance, more seriously. He has his own site; Climatescience.org (I think). You should be able to find his stuff easily enough. I've browsed rather than read in detail, but I will look at his work more carefully when I get the time.

I am concerned by some of your references, which I am sure are simply misunderstandings on my part. ACRIM measures irradiance, not CO2 emissions. Of course variations in irradiance have an effect on surface temperatures, but can you find evidence that directly links the observed temperature increase since, say 1950, with a correlative increase in either sunspot activity or solar irradiance?

It may be Graps' opinion that a doubling of CO2 will result in a warming of only 0.2%, but this does not tally with the findings of others; it needs to be explained. Even Pielke (above) anticipates + 1.3-2.6 as a consequence of doubling (I think).

Finally, the Journal of Lunar & Planetary Science observed that the Gleissberg cycle (80 yrs, give or take) gives 1910 as the last minimum phase, therefore we should already have passed through the next phase (in the 1990's). I can't account for their observation, so I'll leave for you to puzzle out.

TWS, in response to your question, I'm sorry, I don't recall where I picked up that piece of gossip, and I wouldn't testify as to its veracity. The Canadian Climate Research Model, I believe, gives higher end results to the temperature change, due to a higher sensitivity in the model to CO2 forcing.

Cheers.

[BLAST FROM THE PAST]

BFTP, you'll be pleased to know that I have found at least one reputable scientist who has a lot to say on this subject and appears to favour your ideas (though not necessarily your reasons) over the mainstream CO2 forcing lobby; Roger A. Pielke Sr. He runs the Colorado State climate thingy, and seems to be highly respected. He isn't a GW skeptic, as some have labelled him, but he argues extensively about the need to take other forcing mechanisms, especially solar irradiance, more seriously. He has his own site; Climatescience.org (I think). You should be able to find his stuff easily enough. I've browsed rather than read in detail, but I will look at his work more carefully when I get the time.

I am concerned by some of your references, which I am sure are simply misunderstandings on my part. ACRIM measures irradiance, not CO2 emissions. Of course variations in irradiance have an effect on surface temperatures, but can you find evidence that directly links the observed temperature increase since, say 1950, with a correlative increase in either sunspot activity or solar irradiance?

It may be Graps' opinion that a doubling of CO2 will result in a warming of only 0.2%, but this does not tally with the findings of others; it needs to be explained. Even Pielke (above) anticipates + 1.3-2.6 as a consequence of doubling (I think).

Finally, the Journal of Lunar & Planetary Science observed that the Gleissberg cycle (80 yrs, give or take) gives 1910 as the last minimum phase, therefore we should already have passed through the next phase (in the 1990's). I can't account for their observation, so I'll leave for you to puzzle out.

TWS, in response to your question, I'm sorry, I don't recall where I picked up that piece of gossip, and I wouldn't testify as to its veracity. The Canadian Climate Research Model, I believe, gives higher end results to the temperature change, due to a higher sensitivity in the model to CO2 forcing.

Cheers.

Permanides

Thanks for the reference

Re the Gleissberg minima the 80 year cycle is not the same as the predicted minima

There have been a host of publications since the 19th century and especially in recent decades that provided evidence of strong solar-terrestrial relations in meteorology and climate ignored by proponents of man-made global warming (Koppen, 1873; Clough, 1905; Brooks; 1926; Scherhag, 1952; Bossolasco et al., 1973; Reiter, 1983; Eddy, 1976; Hoyt, 1979; Markson, 1980; Schuurmans, 1979; Landscheidt, 1981-2001; Bucha 1983; Herman and Goldberg, 1983; Neubauer 1983; Prohaska and Willett, 1983; Fairbridge and Shirley, 1987; Friis-Christensen and Lassen, 1991; Labitzke and van Loon, 1993; Haigh, 1996; Baliunas and Soon, 1995; Lassen and Friis-Christensen, 1995); Lau and Weng, 1995; Lean et al, 1995; Hoyt and Schatten, 1997; Reid, 1997; Soon et al. 1996; Svensmark and Friis-Christensen, 1997; White et al. 1997; Cliver et al., 1998; Balachandran et al., 1999; Shindell et al., 1999; van Geel et al., 1999; Berner, 2000; Egorova et al., 2000; Palle Bago and Butler, 2000; Tinsley, 2000; Hodell et al., 2001; Neff et al., 2001; Rozelot, 2001; Udelhofen and Cess, 2001; Pang and Yau, 2002; Yu, 2002)

The IPCC's judgement that the solar factor is negligible is based on satellite observations available since 1978 which show that the Sun's total irradiance, though not being constant, changes only by about 0.1 percent during the course of the 11-year sunspot cycle. This argument, however, does not take into account that the Sun's eruptional activity (energetic flares, coronal mass ejections, eruptive prominences), heavily affecting the solar wind, as well as softer solar wind contributions by coronal holes have a much stronger effect than total irradiance. The total magnetic flux leaving the Sun, dragged out by the solar wind, has risen by a factor of 2.3 since 1901 (Lockwood et al., 1999), while global temperature on earth increased by about 0.6°C. The energy in the solar flux is transferred to the near-Earth environment by magnetic reconnection and directly into the atmosphere by charged particles. Energetic flares increase the Sun's ultraviolet radiation by at least 16 percent. Ozone in the stratosphere absorbs this excess energy which causes local warming and circulation disturbances. General circulation models developed by Haigh (1996), Shindell et al. (1999), and Balachandran et al. (1999) confirm that circulation changes, initially induced in the stratosphere, can penetrate into the troposphere and influence temperature, air pressure, Hadley circulation, and storm tracks by changing the distribution of large amounts of energy already present in the atmosphere.

In that list look at Theodore Landscheidt for example.

NB These are references which I'm not saying disprove AGW but have opened up my view and seems to be opening up many more views inasmuch that research now seems to be increasing

BFTP

Edited August 4, 2006 by BLAST FROM THE PAST

[parmenides3]

Thanks for the list. I am aware of Landscheidt's work but don't know what to make of him. His primary field was astrology, but he was clearly a serious amateur climatologist. His publications were produced by his own 'academy', of which he, apparently, was the only published author. Yet he was regularly consulted on climate change and GW. I can't decide how seriously to take his work, so, at the moment, I'll defer judgement.

Friis-Christiansen and Soon, two of the authors you cite, have 'mixed' reputations, and there are published refutations of much of their work, by their peers. Personally, I tend to view their work with great caution. I cannot comment on the others, though I am aware of the work of several of them.

None of this is to suggest that any of the above work is not serious and sincere, but some of it, at least, has been shown to be poor science.

Can you please cite the quotation you provide?

I agree that the solar flux/ cosmic dust issues are not to be taken lightly, but you haven't answered my question; is there a published, demonstrated correlation between solar activity and temperature changes over the last 50 years?

The three GCMs which you cite apparently demonstrate that circulation changes in the stratosphere can penetrate into the troposphere and effect climate locally. This is known and accepted. What they don't do is establish a measurable link between the two phenomena. There has been some work done recently on measuring solar influence over long time scales by analysing 12Be and 14c particles in ice cores, but it is not conclusive. Yu, who you cite, ends the paper by saying that the level of accuracy available to models needs to improve by at least an order of magnitude before a fair conclusion can be hypothesised scientifically.

I really can't get my head round this Gleissberg thing. A minimum of what? Sunspot activity? If so, your argument contains an a priori assumption which has to be shown to be correct before you can draw a conclusion from it, otherwise the conclusion cannot be said to be valid.

Cheers

[VillagePlank]

It's a graph; you'll know I don't trust them by now, but here's a proposition, with the source. I've no idea on the reliability of source, either, or whether the astrophsyics journal is well respected, or not.

This seems like a very well written piece with each 'fact' cross referenced with it's source.

Edited August 4, 2006 by Wilson

[parmenides3]

It's a graph; you'll know I don't trust them by now, but here's a proposition, with the source. I've no idea on the reliability of source, either, or whether the astrophsyics journal is well respected, or not.

This seems like a very well written piece with each 'fact' cross referenced with it's source.

Thanks. I've already read the article; it's a little out of date, but it shows the recognised effects of solar activity on temperature. No problem with this. It doesn't show the Sun as a casue of GW, only of climate change.

Unfortunately, the graph didn't expand, so I couln't read the details or the source; can you supply, please?

Some articles which cover both sides of the debate are featured here. There is plenty of debate about several of them, as highlighted earlier, but feel free to read and offer up suggestions.

Benestad, R.E. (2002) Solar Activity and Earth's Climate, Praxis-Springer, Berlin and Heidelberg, 287pp, ISBN: 3-540-43302-3

Damon, P.E. and P. Laut (2004), Pattern of Strange Errors Plagues Solar Activity and Terrestrial Climate Data, Eos, vol 85, num 39, p. 370

Friis-Christensen, E. and K. Lassen (1991), Length of the solar cycle: an indicator of solar activity closely associated with climate, Science 254: 698-700

Meehl, G.A., W.M. Washington, T.M.L. wigley, J.M. Arblaster, A. Dai (2003): Solar and Greenhouse Gas Forcing and Climate Response in the Twentieth Century, J. Climate, 6: 426-444

Shindell, D., D. Rind, N. Balachandran, J. Lean and P. Lonergan (1999): Solar Cycle Variability, Ozone and Climate, Science, 284: 305-308

Svensmark, H. (1998), Influence of Cosmic Rays on Earth's Climate, Physical Review Letters, vol 81, num 22, 5027-5030

Enjoy.

[VillagePlank]

The source marked on the graph reads 'SOURCE S.Baliunas and W.Soon/Astrophysical Journal' It's referenced here but I can't find the exact article.

A quick Google on the author's shows at least Balinus to be somewhat sceptical of AGW here

Here is one for the sceptics.

This is fun. Pick a point of view and you can get any info you need to support it

Edited August 4, 2006 by Wilson

[parmenides3]

Source; Mann & Schmidt, 2005. (with apologies)

There have been several recent cases of putatively peer-reviewed studies in the scientific literature that produced unjustified or invalid conclusions. Curiously, many of these publications have been accompanied by heavy publicity campaigns, often declaring that this one paper completely refutes the scientific consensus. An excellent account of some of these examples is provided here by Dr. Stephen Schneider (Stanford University).

Perhaps the most publicized recent example was the publication of a study by astronomer Willie Soon of the Harvard University-affiliated Harvard-Smithsonian Center for Astrophysics and co-authors, claiming to demonstrate that 20th century global warmth was not unusual in comparison with conditions during Medieval times. Indeed, this study serves as a prime example of one of the "myths" that we have debunked elsewhere on this site. The study was summarily discredited in articles by teams of climate scientists (including several of the scientists here at RealClimate), in the American Geophysical Union (AGU) journal Eos and in Science. However, it took some time the rebuttals to work their way through the slow process of the scientific peer review. In the meantime the study was quickly seized upon by those seeking to sow doubt in the validity behind the scientific consensus concerning the evidence for human-induced climate change (see news articles in the New York Times, and Wall Street Journal). The publication of the study had wider reverberations throughout the academic and scientific institutions connected with it. The association of the study with the "Harvard" name caused some notable unease among members of the Harvard University community (see here and here) and the reputation of the journal publishing the study was seriously tarnished in the process. The editor at Climate Research that handled the Soon et al paper, Dr. Chris de Frietas, has a controversial record of past editorial practices (see this 'sidebar' to an article in Scientific American by science journalist David Appell). In an unprecedented (to our knowledge) act of protest, chief editor Hans von Storch and 3 additional editors subsequently resigned from Climate Research in response to the fundamental documented failures of the editorial process at the journal. A detailed account of these events are provided by Chris Mooney in the Skeptical Inquirer and The American Prospect, by David Appell in Scientific American, and in a news brief in Nature. The journal's publisher himself (Otto Kline) eventually stated that "[the conclusions drawn]cannot be concluded convincingly from the evidence provided in the paper".

You're right, you can find material to support any view, but can you find evidence, hard, scientific evidence? With the exception (so far) of Pielke, none of the 'evidence' anyone has cited in challenging the current consensus has held up against serious scrutiny, which is one reason, but not the only reason, why I am satisfied to go with the consensus view on this.

edit: Wikipedia has an article on Soon & Baliunas

Edited August 4, 2006 by parmenides3

[VillagePlank]

You're right, you can find material to support any view, but can you find evidence, hard, scientific evidence?

Indeed; that is the crux of the matter

[parmenides3]

Indeed; that is the crux of the matter

So, what would you like evidence of? Ignoring the GCMs for the moment (a debatable point, but one which we can allow), what is it you lack evidence for that you would like to see established? Rather than deal with future hypotheses, would you prefer to deal with measured records? Ask, and I'll look & respond. I am open-minded on this.

[Guest Viking141]

I have been following this debate with great interest. Can I say first of all that I accept we are in a warming phase and I also accept that part of this is down to humans. What I disagree with is how much can be put down to human influence and what the future holds.

In that respect I would like to ask this question:

What thought has been given to and has any research been done on the possibility that what humans may be contributing to is not AGW but a forthcoming Dansgaard-Oeschger event, a rapid climate fluctuation typically starting with a rapid warming episode over a few decades (as we are seeing now) followed by a longer cooling phase including glaciation?

I look forward to your replies.

Viking

[Guest Mike W]

No chance of us causing a glaciation, IMO anyway.

Edited August 4, 2006 by Mike W

[BLAST FROM THE PAST]

Type in TIMO NIROMA in GOOGLE for gleissberg minima and cycles, very complicated to post so better off reading that...a good read. Re Amara GRAPS type in 'Global warming and solar variability' and it should come up...Amara GRAPS response/quote is in that.

Can't show you but NASA have shown 0.05% increase in solar irradiance every decade since 70s, that is a good start. Also recent 'minima' are actually low maxima and don't correlate to true solar minimas. Rather you read the stuff than get it from me second hand.

As for evidence there is no evidence either that CO2 is causation or consequence...to many ifs or buts and too many 'scientists' at loggerheads

BFTP

I have been following this debate with great interest. Can I say first of all that I accept we are in a warming phase and I also accept that part of this is down to humans. What I disagree with is how much can be put down to human influence and what the future holds.

In that respect I would like to ask this question:

What thought has been given to and has any research been done on the possibility that what humans may be contributing to is not AGW but a forthcoming Dansgaard-Oeschger event, a rapid climate fluctuation typically starting with a rapid warming episode over a few decades (as we are seeing now) followed by a longer cooling phase including glaciation?

I look forward to your replies.

Viking

Viking

interesting point read the 200 solar cycle link...google it

BFTP

[Thundery wintry showers]

I had a quick scan of the link and I couldn't help but notice that it was littered with 'could's' and 'may' and 'might' and 'it is possible that', which illustrates the point that should be obvious to everyone and that is as difficult as it is to forecast a week in advance there is no way that 100 years can be forecasted to any reliable degree. Sure there is the hockey stick graph and the rises in CO2 but there is also sunspot cycles and synoptics and possible NAD disruption, etc.

I am not anti-AGW, I would have to be a fool to be, but similarly only a fool would swallow some of the propaganda (from both sides of the fence) because at the end of the day most of it is guesswork, and the arrogance of some climatologists who presume that they can definitively say what the future holds re. GW can be astounding.

I have to come clean and admit I haven't read the report yet, but the above description suggests to me that it's probably a reasoned and balanced report. "Could", "may" and "might" and "it is possible that" are perfect words to use to describe our current state of certainty over climate change.

[parmenides3]

Dealing with several points, following yesterday's dinner/birthday party (not mine).

Viking: I don't know what research is being done on this at the moment, but here are some thoughts about Dansgaard-Oeschger events. [For those who don't know: periods of warming followed by periods of cooling, discovered through analysis of ice-cores in Greenland and elsewhere].

First: these events describe climate change during historical ice ages. As such, it is unclear whether they relate to climate change during interglacials.

Second: this kind of event occurs on a centuries-millenial timescale, (which is 'rapid' in palaeoclimatic terms) and is characterised by changes in temperature, in total, of 8-16 degrees. Over, say 1000 years, we might then expect a variation or trend that amounts to ~0.8>1.6C over a centuries timescale, or ~0.08>0.16C over a decadal scale. Whilst significant over a sufficient period of time, it would be hard to seperate such a figure from the temperature records with a meaningful degree of confidence.

Third: there have been suggestions that 'weakened' versions of such events occur in ~1470 year cycles. This is as yet unproven. It has been suggested (note; suggested), that this might account for the 'Roman' and 'Little' ice ages. If this were the case, we might reasonably expect the next 'phase' to occur in the latter half of the third millenium, rather than in the foreseeable future.

A probable precursor of D-O events is a Heinrich event - a shut-down of the thermohaline ciculation in the North Atlantic. I suppose it could be reasonably argued that we could be entering a Heinrich event phase now/ in the near future. If that were the case, we would be expecting a continuation of warming & an increase of ocean desalinisation for decades-centuries yet.

Finally, it is an interesting idea that this may be the case, but even if it were, it would not account for the changes in climate we have had since the mid-twentieth century, as the speed and scale of climate change do not, in any way, match, so, as an explanation for GW (it is, after all, a record of climate change, not GW), it is insufficient, therefore can be added to the list of things to consider when analysing climate change, rather than the list of explanations as to why our climate is warming so rapidly.

BFTP. When I followed your suggestion, I came up with a response from Graps to a blog/forum comment; it seemed to match what you were saying. The response was written by Graps when he was a member of the Stanford Solar research team in 1997. In the response, Graps says (paraphrasing); it is to soon to tell what the influence of the Sun on climate is (lack of data); that not enough is known about other mechanisms, such as dust particles, to be confident about the stregth of the connection between Solar activity and Earth temperatures, and that the degree of fluctuations relating to El Nino cycles was much stronger than those observed (at that time) from variations in Solar activity.

This is what I cherry-picked of the same Stanford Solar research site this morning: (with apologies to the authors)

Global warming -- a gradual increase in planet-wide temperatures -- is now well documented and accepted by scientists as fact. A panel convened by the U.S National Research Council, the nation's premier science policy body, in June 2006 voiced a "high level of confidence" that Earth is the hottest it has been in at least 400 years, and possibly even the last 2,000 years. Studies indicate that the average global surface temperature has increased by approximately 0.5-1.0°F (0.3-0.6°C) over the last century. This is the largest increase in surface temperature in the last 1,000 years and scientists are predicting an even greater increase over this century. This warming is largely attributed to the increase of greenhouse gases (primarily carbon dioxide and methane) in the Earth's upper atmosphere caused by human burning of fossil fuels, industrial, farming, and deforestation activities.

--------------------------------------------------------------------------------

Factors

Greenhouse Gases

The increase in greenhouse gases caused by human activity is often cited as one of the major causes of global warming. These greenhouse gases reabsorb heat reflected from the Earth's surface, thus trapping the heat in our atmosphere. This natural process is essential for life on Earth because it plays an important role in regulating the Earth's temperature. However, over the last several hundred years, humans have been artificially increasing the concentration of these gases, mainly carbon dioxide and methane in the Earth's atmosphere. These gases build up and prevent additional thermal radiation from leaving the Earth, thereby trapping excess heat.

"Power plants, cattle, and cars are some of the major contributors of greenhouse gases such as carbon dioxide and methane."- Earth Observatory Global Warming Article

Image Credit: NASA's Earth Observatory

Solar Variability & Global Warming

Some uncertainty remains about the role of natural variations in causing climate change. Solar variability certainly plays a minor role, but it looks like only a quarter of the recent variations can be attributed to the Sun. At most. During the initial discovery period of global warming, the magnitude of the influence of increased activity on the Sun was not well determined.

Solar irradiance changes have been measured reliably by satellites for only 30 years. These precise observations show changes of a few tenths of a percent that depend on the level of activity in the 11-year solar cycle. Changes over longer periods must be inferred from other sources. Estimates of earlier variations are important for calibrating the climate models. While a component of recent global warming may have been caused by the increased solar activity of the last solar cycle, that component was very small compared to the effects of additional greenhouse gases. According to a NASA Goddard Institute for Space Studies (GISS) press release, "...the solar increases do not have the ability to cause large global temperature increases...greenhouse gases are indeed playing the dominant role..." The Sun is once again less bright as we approach solar minimum, yet global warming continues.

As for your last comment; I am sorry, but I have to disagree. There is a mountain of evidence that CO2 is the principle cause of Global Warming. There are plenty of nay-sayers, but, with the exception of Pielke Sr. (cited previously), very few 'scientists' of repute who have offered reasoned alternative explanations. Almost all of 'scientists' who contest this conclusion have been found to be either incorrect in their reasoning or, much worse, funded by the petrochemical industry or Conservative US lobby groups (the two are not the same).

Any questions?

Oh, and thanks to you all for encouraging me to find this stuff; it's fun.

[Guest Mike W]

I thought water vapour or water was a bigger warming agent than CO2.

[parmenides3]

I thought water vapour or water was a bigger warming agent than CO2.

Sorry, you'll have to be a bit clearer. Do you mean that water vapour contributes to the climate as a feedback mechanism, or are you suggesting that water vapour is a cause of warming, or something else entirely?

[Guest Viking141]

Dealing with several points, following yesterday's dinner/birthday party (not mine).

Viking: I don't know what research is being done on this at the moment, but here are some thoughts about Dansgaard-Oeschger events. [For those who don't know: periods of warming followed by periods of cooling, discovered through analysis of ice-cores in Greenland and elsewhere].

First: these events describe climate change during historical ice ages. As such, it is unclear whether they relate to climate change during interglacials.

Second: this kind of event occurs on a centuries-millenial timescale, (which is 'rapid' in palaeoclimatic terms) and is characterised by changes in temperature, in total, of 8-16 degrees. Over, say 1000 years, we might then expect a variation or trend that amounts to ~0.8>1.6C over a centuries timescale, or ~0.08>0.16C over a decadal scale. Whilst significant over a sufficient period of time, it would be hard to seperate such a figure from the temperature records with a meaningful degree of confidence.

Third: there have been suggestions that 'weakened' versions of such events occur in ~1470 year cycles. This is as yet unproven. It has been suggested (note; suggested), that this might account for the 'Roman' and 'Little' ice ages. If this were the case, we might reasonably expect the next 'phase' to occur in the latter half of the third millenium, rather than in the foreseeable future.

A probable precursor of D-O events is a Heinrich event - a shut-down of the thermohaline ciculation in the North Atlantic. I suppose it could be reasonably argued that we could be entering a Heinrich event phase now/ in the near future. If that were the case, we would be expecting a continuation of warming & an increase of ocean desalinisation for decades-centuries yet.

Finally, it is an interesting idea that this may be the case, but even if it were, it would not account for the changes in climate we have had since the mid-twentieth century, as the speed and scale of climate change do not, in any way, match, so, as an explanation for GW (it is, after all, a record of climate change, not GW), it is insufficient, therefore can be added to the list of things to consider when analysing climate change, rather than the list of explanations as to why our climate is warming so rapidly.

Thanks for that. Is it not possible that we could be heading for a D-O event, that we are already in the early stages of a Heinrich Event and that although the next such phase in the normal timetable would be some 80-odd years off (approx 2090) is it not possible that the human influence is what is causing the more rapid temp rise and that the human influence is bringing forward a possible D-O event by several decades? Is it not possible that if, as has been suggested, the human race has influenced climate change due to our burning of fossil fuels, we could in fact be preciptating the early arrival of a D-O event and not the AGW that others suggest?

Is it not the case that on all previous occasions global warming has inevitably been followed by a period of sustained cooling resulting in either full or limited glaciations?

Human beings, in particular those of the scientific variety, can be quite arrogant at times. We assume that our impact on the globe matters hugely. It seems to me that on the grand scheme of things our impact is limited compared to the awesome natural forces at work on our planet. Is it not the case that we are, in all likelihood merely adding to an already ongoing cycle?

[Devonian]

Here is the recent history of solar output. If anyone can see a solar warming trend perhaps they could point it out?