Rickster71

Rickster71

Audioholic Spartan
A little long, yet interesting

Very true....

The earth has been warming and CO2 levels have increased for more than 10,000 years. The earth has warmed since the retreat of the most recent ice age. (a mere 10,000 year blink of the eye in geologic terms)

On the other hand, the topic of an environmentalist concocted man made global warming is an entirely different topic in itself. The reality is that many major ice ages have come and gone in the past, and they will continue to do so in the future...... whether we like it or not. Kick back, relax, and enjoy........ because we live during a most fortunate time period within that cycle.

Well said, by you and others. I must agree Buckeye!
Below is a little tid-bit worth reading. IMHO


From The Sunday Times
February 11, 2007

An experiment that hints we are wrong on climate change
Nigel Calder, former editor of New Scientist, says the orthodoxy must be challenged
When politicians and journalists declare that the science of global warming is settled, they show a regrettable ignorance about how science works. We were treated to another dose of it recently when the experts of the Intergovernmental Panel on Climate Change issued the Summary for Policymakers that puts the political spin on an unfinished scientific dossier on climate change due for publication in a few months’ time. They declared that most of the rise in temperatures since the mid-20th century is very likely due to man-made greenhouse gases.

The small print explains “very likely” as meaning that the experts who made the judgment felt 90% sure about it. Older readers may recall a press conference at Harwell in 1958 when Sir John Cockcroft, Britain’s top nuclear physicist, said he was 90% certain that his lads had achieved controlled nuclear fusion. It turned out that he was wrong. More positively, a 10% uncertainty in any theory is a wide open breach for any latterday Galileo or Einstein to storm through with a better idea. That is how science really works.

Twenty years ago, climate research became politicised in favour of one particular hypothesis, which redefined the subject as the study of the effect of greenhouse gases. As a result, the rebellious spirits essential for innovative and trustworthy science are greeted with impediments to their research careers. And while the media usually find mavericks at least entertaining, in this case they often imagine that anyone who doubts the hypothesis of man-made global warming must be in the pay of the oil companies. As a result, some key discoveries in climate research go almost unreported.

Enthusiasm for the global-warming scare also ensures that heatwaves make headlines, while contrary symptoms, such as this winter’s billion-dollar loss of Californian crops to unusual frost, are relegated to the business pages. The early arrival of migrant birds in spring provides colourful evidence for a recent warming of the northern lands. But did anyone tell you that in east Antarctica the Adélie penguins and Cape petrels are turning up at their spring nesting sites around nine days later than they did 50 years ago? While sea-ice has diminished in the Arctic since 1978, it has grown by 8% in the Southern Ocean.

Background
‘Blame cosmic rays for warming up the planet’

So one awkward question you can ask, when you’re forking out those extra taxes for climate change, is “Why is east Antarctica getting colder?” It makes no sense at all if carbon dioxide is driving global warming. While you’re at it, you might inquire whether Gordon Brown will give you a refund if it’s confirmed that global warming has stopped. The best measurements of global air temperatures come from American weather satellites, and they show wobbles but no overall change since 1999.

That levelling off is just what is expected by the chief rival hypothesis, which says that the sun drives climate changes more emphatically than greenhouse gases do. After becoming much more active during the 20th century, the sun now stands at a high but roughly level state of activity. Solar physicists warn of possible global cooling, should the sun revert to the lazier mood it was in during the Little Ice Age 300 years ago.

Climate history and related archeology give solid support to the solar hypothesis. The 20th-century episode, or Modern Warming, was just the latest in a long string of similar events produced by a hyperactive sun, of which the last was the Medieval Warming.

The Chinese population doubled then, while in Europe the Vikings and cathedral-builders prospered. Fascinating relics of earlier episodes come from the Swiss Alps, with the rediscovery in 2003 of a long-forgotten pass used intermittently whenever the world was warm.

What does the Intergovernmental Panel do with such emphatic evidence for an alternation of warm and cold periods, linked to solar activity and going on long before human industry was a possible factor? Less than nothing. The 2007 Summary for Policymakers boasts of cutting in half a very small contribution by the sun to climate change conceded in a 2001 report.

Disdain for the sun goes with a failure by the self-appointed greenhouse experts to keep up with inconvenient discoveries about how the solar variations control the climate. The sun’s brightness may change too little to account for the big swings in the climate. But more than 10 years have passed since Henrik Svensmark in Copenhagen first pointed out a much more powerful mechanism.

He saw from compilations of weather satellite data that cloudiness varies according to how many atomic particles are coming in from exploded stars. More cosmic rays, more clouds. The sun’s magnetic field bats away many of the cosmic rays, and its intensification during the 20th century meant fewer cosmic rays, fewer clouds, and a warmer world. On the other hand the Little Ice Age was chilly because the lazy sun let in more cosmic rays, leaving the world cloudier and gloomier.

The only trouble with Svensmark’s idea — apart from its being politically incorrect — was that meteorologists denied that cosmic rays could be involved in cloud formation. After long delays in scraping together the funds for an experiment, Svensmark and his small team at the Danish National Space Center hit the jackpot in the summer of 2005.

In a box of air in the basement, they were able to show that electrons set free by cosmic rays coming through the ceiling stitched together droplets of sulphuric acid and water. These are the building blocks for cloud condensation. But journal after journal declined to publish their report; the discovery finally appeared in the Proceedings of the Royal Society late last year.

Thanks to having written The Manic Sun, a book about Svensmark’s initial discovery published in 1997, I have been privileged to be on the inside track for reporting his struggles and successes since then. The outcome is a second book, The Chilling Stars, co-authored by the two of us and published next week by Icon books. We are not exaggerating, we believe, when we subtitle it “A new theory of climate change”.

Where does all that leave the impact of greenhouse gases? Their effects are likely to be a good deal less than advertised, but nobody can really say until the implications of the new theory of climate change are more fully worked out.

The reappraisal starts with Antarctica, where those contradictory temperature trends are directly predicted by Svensmark’s scenario, because the snow there is whiter than the cloud-tops. Meanwhile humility in face of Nature’s marvels seems more appropriate than arrogant assertions that we can forecast and even control a climate ruled by the sun and the stars.

The Chilling Stars is published by Icon. It is available for £9.89 including postage from The Sunday Times Books First on 0870 165 8585
 
stratman

stratman

Audioholic Ninja
Well said, by you and others. I must agree Buckeye!
Below is a little tid-bit worth reading. IMHO


From The Sunday Times
February 11, 2007

An experiment that hints we are wrong on climate change
Nigel Calder, former editor of New Scientist, says the orthodoxy must be challenged
When politicians and journalists declare that the science of global warming is settled, they show a regrettable ignorance about how science works. We were treated to another dose of it recently when the experts of the Intergovernmental Panel on Climate Change issued the Summary for Policymakers that puts the political spin on an unfinished scientific dossier on climate change due for publication in a few months’ time. They declared that most of the rise in temperatures since the mid-20th century is very likely due to man-made greenhouse gases.

The small print explains “very likely” as meaning that the experts who made the judgment felt 90% sure about it. Older readers may recall a press conference at Harwell in 1958 when Sir John Cockcroft, Britain’s top nuclear physicist, said he was 90% certain that his lads had achieved controlled nuclear fusion. It turned out that he was wrong. More positively, a 10% uncertainty in any theory is a wide open breach for any latterday Galileo or Einstein to storm through with a better idea. That is how science really works.

Twenty years ago, climate research became politicised in favour of one particular hypothesis, which redefined the subject as the study of the effect of greenhouse gases. As a result, the rebellious spirits essential for innovative and trustworthy science are greeted with impediments to their research careers. And while the media usually find mavericks at least entertaining, in this case they often imagine that anyone who doubts the hypothesis of man-made global warming must be in the pay of the oil companies. As a result, some key discoveries in climate research go almost unreported.

Enthusiasm for the global-warming scare also ensures that heatwaves make headlines, while contrary symptoms, such as this winter’s billion-dollar loss of Californian crops to unusual frost, are relegated to the business pages. The early arrival of migrant birds in spring provides colourful evidence for a recent warming of the northern lands. But did anyone tell you that in east Antarctica the Adélie penguins and Cape petrels are turning up at their spring nesting sites around nine days later than they did 50 years ago? While sea-ice has diminished in the Arctic since 1978, it has grown by 8% in the Southern Ocean.

Background
‘Blame cosmic rays for warming up the planet’

So one awkward question you can ask, when you’re forking out those extra taxes for climate change, is “Why is east Antarctica getting colder?” It makes no sense at all if carbon dioxide is driving global warming. While you’re at it, you might inquire whether Gordon Brown will give you a refund if it’s confirmed that global warming has stopped. The best measurements of global air temperatures come from American weather satellites, and they show wobbles but no overall change since 1999.

That levelling off is just what is expected by the chief rival hypothesis, which says that the sun drives climate changes more emphatically than greenhouse gases do. After becoming much more active during the 20th century, the sun now stands at a high but roughly level state of activity. Solar physicists warn of possible global cooling, should the sun revert to the lazier mood it was in during the Little Ice Age 300 years ago.

Climate history and related archeology give solid support to the solar hypothesis. The 20th-century episode, or Modern Warming, was just the latest in a long string of similar events produced by a hyperactive sun, of which the last was the Medieval Warming.

The Chinese population doubled then, while in Europe the Vikings and cathedral-builders prospered. Fascinating relics of earlier episodes come from the Swiss Alps, with the rediscovery in 2003 of a long-forgotten pass used intermittently whenever the world was warm.

What does the Intergovernmental Panel do with such emphatic evidence for an alternation of warm and cold periods, linked to solar activity and going on long before human industry was a possible factor? Less than nothing. The 2007 Summary for Policymakers boasts of cutting in half a very small contribution by the sun to climate change conceded in a 2001 report.

Disdain for the sun goes with a failure by the self-appointed greenhouse experts to keep up with inconvenient discoveries about how the solar variations control the climate. The sun’s brightness may change too little to account for the big swings in the climate. But more than 10 years have passed since Henrik Svensmark in Copenhagen first pointed out a much more powerful mechanism.

He saw from compilations of weather satellite data that cloudiness varies according to how many atomic particles are coming in from exploded stars. More cosmic rays, more clouds. The sun’s magnetic field bats away many of the cosmic rays, and its intensification during the 20th century meant fewer cosmic rays, fewer clouds, and a warmer world. On the other hand the Little Ice Age was chilly because the lazy sun let in more cosmic rays, leaving the world cloudier and gloomier.

The only trouble with Svensmark’s idea — apart from its being politically incorrect — was that meteorologists denied that cosmic rays could be involved in cloud formation. After long delays in scraping together the funds for an experiment, Svensmark and his small team at the Danish National Space Center hit the jackpot in the summer of 2005.

In a box of air in the basement, they were able to show that electrons set free by cosmic rays coming through the ceiling stitched together droplets of sulphuric acid and water. These are the building blocks for cloud condensation. But journal after journal declined to publish their report; the discovery finally appeared in the Proceedings of the Royal Society late last year.

Thanks to having written The Manic Sun, a book about Svensmark’s initial discovery published in 1997, I have been privileged to be on the inside track for reporting his struggles and successes since then. The outcome is a second book, The Chilling Stars, co-authored by the two of us and published next week by Icon books. We are not exaggerating, we believe, when we subtitle it “A new theory of climate change”.

Where does all that leave the impact of greenhouse gases? Their effects are likely to be a good deal less than advertised, but nobody can really say until the implications of the new theory of climate change are more fully worked out.

The reappraisal starts with Antarctica, where those contradictory temperature trends are directly predicted by Svensmark’s scenario, because the snow there is whiter than the cloud-tops. Meanwhile humility in face of Nature’s marvels seems more appropriate than arrogant assertions that we can forecast and even control a climate ruled by the sun and the stars.

The Chilling Stars is published by Icon. It is available for £9.89 including postage from The Sunday Times Books First on 0870 165 8585
Like I've said many times before, there's no consensus on the matter, too many variables and once science becomes politicized it gets harder to come to unbiased conclusions.
 
Tomorrow

Tomorrow

Audioholic Ninja
Like I've said many times before, there's no consensus on the matter, too many variables and once science becomes politicized it gets harder to come to unbiased conclusions.
I haven't read this entire thread...so pardon if this has been discussed.

But I understand that both Mars and Neptune are displaying unprecedented planetary warming. (Maybe they have cloaking devices on all the greenhouse gas production devices. :eek:) It has not been disproved, so far as I know, that the climatological changes we see aren't solar created.

Certainty belongs to True Believers. Doubt and research are for (real) scientists.
 
stratman

stratman

Audioholic Ninja
I haven't read this entire thread...so pardon if this has been discussed.

But I understand that both Mars and Neptune are displaying unprecedented planetary warming. (Maybe they have cloaking devices on all the greenhouse gas production devices. :eek:) It has not been disproved, so far as I know, that the climatological changes we see aren't solar created.

Certainty belongs to True Believers. Doubt and research are for (real) scientists.
Well what do you expect? Those dang Martians and their un-green (or is it un-red? it's Mars you know) SUVs, we need to fly ol' Mr. 2x4 (Gore) and show those rascals how to behave green....er.. ah, red I mean! Maybe Michael Moore can do an un-biased "documentary" on Martian corporate selfishness..."On a clear day I can see the Earth." Or Martian gun-love..."Bowling for my phasor."
 
stratman

stratman

Audioholic Ninja
Don't get me going on the the Neptunians, they think it's the 1960s all over again, muscle-buggies everywhere, 8 mpg on a good day.
 
Tomorrow

Tomorrow

Audioholic Ninja
Don't get me going on the the Neptunians, they think it's the 1960s all over again, muscle-buggies everywhere, 8 mpg on a good day.
They've apparently already killed off all the trees there. And yep, muscle-buggies blasting the latest Nep-Tunes with annoying, big honkin' subterrainianwoofer systems. I hate those guys. ;)
 
T

tbewick

Senior Audioholic
Rickster 57,

I read your post about global warming and have a few comments:

Uneven temperature variations around the world:

This is recognised in climate modelling studies and in the IPCC report. The temperature change recorded over 20th century is a global change, and is shown in the temperature record and in geographic changes around the world. The recent IPCC Working Group II report analysed over 80,000 datasets of measurements across the world on biological systems, and the results of these measurements are in-line with predicted levels of warming. The IPCC report also recognises that temperature changes will vary regionally from the global average in different parts of the world.

Solar activity versus man-made greenhouse gas effect:

The established link between cosmic rays and variation in the global average temperature is a statistical one. The physical explanation of how cosmic rays affect the climate through altering cloud formation is at a very early stage of development. There has been experiments to see how cosmic rays could affect clouds through the formation of cloud nuclei, but these experiments are still some way from making predictions which can be tested in the real climate system. High-precision mesurements have been made since the 1980's of variations in the sun's output. These have shown very little change in solar activity over this period*. Over this time, global average temperatures have risen.

In comparision, the physical basis for the greenhouse effect is well-established. The greenhouse effect keeps the temperature of the earth around 30 degrees celsius warmer than it otherwise would be. Man's activities have altered the concentration of carbon dioxide in the atmosphere. Concentrations are at a higher level now than they have been for half a million years. Along with other greenhouse gases like methane, the forcing is now around +2.5 watts per metre squared compared to pre-industrial times. This radiative forcing dominates all the other measured forcings, and the total forcing due to human activites is an order of magnitude greater than all of the other forcings, including solar variability. This alteration in the external forcing of the climate, which is based on rigorous physical calculations, is equivalent to more than double of all the energy man currently generates.

Medieval warm period etc:

If it was found that there were warmer periods in the past than there are now, the attribution of human activity altering the climate would be unaffected. What is important is the rate of warming rather than the actual temperature level. Attribution studies using palaeoclimate studies (which have considered variations in the solar output) over the past 1000 years have shown that the rate of global temperature increase experienced in the late 20th century are unprecedented when compared rates of the last 400 years or so**. Strangely enough, larger variations in the past climate would be suggestive of a higher climate sensitivity, implying greater levels of warming in the future due to GHG emissions.

For more information, please consult this excellent National Research Council Report, 'Climate Science: An Analysis of Some Key Questions':

http://www.nap.edu/html/climatechange/

I should also say that all of the issues you mentioned are discussed in the full IPCC Working Group I report - www.ipcc.ch

* The UK Meteorological office, http://www.metoffice.gov.uk/corporate/pressoffice/myths/index.html

** National Research Council Report, 'Surface Temperature Reconstructions of the Past 2,000 Years'
http://books.nap.edu/openbook.php?record_id=11676&page=R1
 
Tomorrow

Tomorrow

Audioholic Ninja
tbewick,

You have quoted some powerful science, but assumptions were still made, such as cyclic sequencing probabilities as one example. That's a problem. What is the proper length of an epochal warming cycle period? And you know...with all the science behind climatology (and even paleoclimatology to some extent), you'd think we'd be able to get reliable two-day weather forecasts. :rolleyes: But sadly...no.

Strangely enough, a good friend of mine is a paleobiologist (chair at Yale). He believes that human caused global warming is now a foregone fact and isn't subject to complex causation or unknown factors or relationships. (And yet...he still can't say with certainty, only speculatively, as to what killed off the dynosaurs. ;)) There are much simpler issues that defy science. But few are so politicized as global warming.

Also, I wonder about your statement that (man-caused) "greenhouse effect keeps the temperature of the earth around 30 degrees celsius warmer than it otherwise would be". Are you saying it should be MINUS 20 degrees celsius outside my house right now? I need further explanation, please.

Finally, I think a certain amount of doubt is still a healthy approach to this issue specifically, and stated scientific 'fact' generally. But dialog is certainly a doorway to proof and truth.
 
jonnythan

jonnythan

Audioholic Ninja
Also, I wonder about your statement that (man-caused) "greenhouse effect keeps the temperature of the earth around 30 degrees celsius warmer than it otherwise would be". Are you saying it should be MINUS 20 degrees celsius outside my house right now? I need further explanation, please.
He didn't say that *man-caused* greenhouse effects keep the planet +30C. He said that the greenhouse effect *in general* keeps the planet +30C.

"In comparision, the physical basis for the greenhouse effect is well-established. The greenhouse effect keeps the temperature of the earth around 30 degrees celsius warmer than it otherwise would be"
 
Tomorrow

Tomorrow

Audioholic Ninja
He didn't say that *man-caused* greenhouse effects keep the planet +30C. He said that the greenhouse effect *in general* keeps the planet +30C.

"In comparision, the physical basis for the greenhouse effect is well-established. The greenhouse effect keeps the temperature of the earth around 30 degrees celsius warmer than it otherwise would be"
I'm sure he can speak for himself, jonnythan.

EXACTLY what he said was...
The greenhouse effect keeps the temperature of the earth around 30 degrees celsius warmer than it otherwise would be. Man's activities have altered the concentration of carbon dioxide in the atmosphere. Concentrations are at a higher level now than they have been for half a million years. Along with other greenhouse gases like methane, the forcing is now around +2.5 watts per metre squared compared to pre-industrial times. This radiative forcing dominates all the other measured forcings, and the total forcing due to human activites is an order of magnitude greater than all of the other forcings, including solar variability. ]
I read this as man being the primary cause of the 30 degree celsius push. If he means otherwise, I would like to so hear.
 
jonnythan

jonnythan

Audioholic Ninja
I read this as man being the primary cause of the 30 degree celsius push. If he means otherwise, I would like to so hear.
I don't see any possible way you could read that into what he said.

He specifically said:
"The greenhouse effect keeps the temperature of the earth around 30 degrees celsius warmer than it otherwise would be."

He then went on to say how mankind is increasing the level of greenhouse gases in the atmosphere.

I think your misunderstanding comes from a misunderstanding of the greenhouse effect. The greenhouse effect predates man.

His statement said absolutely nothing about "man-caused" greenhouse effect, and, in your previous post, you had to insert it in parentheses outside of the quote. That should tell you something.
 
Tomorrow

Tomorrow

Audioholic Ninja
I don't see any possible way you could read that into what he said.

He specifically said:
"The greenhouse effect keeps the temperature of the earth around 30 degrees celsius warmer than it otherwise would be."

He then went on to say how mankind is increasing the level of greenhouse gases in the atmosphere.

I think your misunderstanding comes from a misunderstanding of the greenhouse effect. The greenhouse effect predates man.

His statement said absolutely nothing about "man-caused" greenhouse effect, and, in your previous post, you had to insert it in parentheses outside of the quote. That should tell you something.

Well I guess you don't believe tbewick can speak for himself.

Jonnythan, I am interested in and requested his clarification of his beliefs as to the affecting nature of man regarding the degree of warming/greenhouse effect. I'm really not interested in your opinion of what he said, or your opinion of what how I interpreted what he said, or your opinion of my knowledge level regarding the matter.
 
jonnythan

jonnythan

Audioholic Ninja
Well I guess you don't believe tbewick can speak for himself.

Jonnythan, I am interested in and requested his clarification of his beliefs as to the affecting nature of man regarding the degree of warming/greenhouse effect. I'm really not interested in your opinion of what he said, or your opinion of what how I interpreted what he said, or your opinion of my knowledge level regarding the matter.
I'm sorry, I thought you were interested in the effects of greenhouse gases on the planet. I was clarifying his statements because they confused you.
 
T

tbewick

Senior Audioholic
Hi Tomorrow,

Sorry, I should have been clear in saying that the +30 degrees difference in the Earth's temperature is due to the natural greenhouse effect. You can explain this with some physics which I've grabbed from some of my lecture notes. The balanced flux model is based on there being a balance between the absorbed solar radiation and that emitted by the surface and atmosphere of the Earth. The simplest way of doing this assumes the Earth emits radiation characteristic of a black body of temperature T(E). The energy from the sun reaching the top of the atmosphere is 1370 watts per metre squared (the solar constant, S). Taking the radius of the Earth to be R, in this simple model the Earth absorbs energy over an area of pi multiplied by (R squared), which is the area 'facing' the sun. The energy is emitted by the Earth over an area of 4 x pi x (R squared), which is the entire surface area of the Earth. A black body at temperature T emits a known amount of energy, E, given by the Stefan-Boltzmann law, E = sigma x (T to the power 4). Sigma is Stefan's constant, equal to 5.67 x (10 ^-8) W (m^-2) (K^-4). Assuming the Earth to be a black body we can equate the absorbed solar flux to the outgoing infra-read energy using Stefan's law:

Energy in = Energy out
(1370 W m^2) x (pi x R^2) = [sigma x T(E)^4] x [4 x pi x R^2]

rearranging gives T(E)^4, therefore T(E) = 279 K.

This is fairly close to the correct surface temperature, but this is because there are two large and compensating errors in the model. To make a better model, the energy absorptive properties of the Earth's atmosphere need to be considered, and the fact that some radiation is reflected back into space by clouds. If we assume 30% of incoming solar radiation is reflected, this alters the calculated surface temperature to 255 K. Allowing for the presence of the Earth's atmosphere and the greenhouse effect gives a surface temperature of 289 K and an atmospheric temperature of 251 K.

I appreciate what you've said about the need for discussion of the subject, but Rickster71's give the impression that these issues are separated from the body of the scientific literature and the IPCC report. Solar forcing of the climate is discussed in Chapter 2 of the IPCC Working Group I fourth assessment report. The explanation for the assigned probability of attributing human activites to the recently observed warming is discussed in chapter 9. The National Research Council reports I referred to earlier were produced by committees of scientists with considerable expertise and experience.
 
Tomorrow

Tomorrow

Audioholic Ninja
Hi Tomorrow,

Sorry, I should have been clear in saying that the +30 degrees difference in the Earth's temperature is due to the natural greenhouse effect. You can explain this with some physics which I've grabbed from some of my lecture notes. The balanced flux model is based on there being a balance between the absorbed solar radiation and that emitted by the surface and atmosphere of the Earth. The simplest way of doing this assumes the Earth emits radiation characteristic of a black body of temperature T(E). The energy from the sun reaching the top of the atmosphere is 1370 watts per metre squared (the solar constant, S). Taking the radius of the Earth to be R, in this simple model the Earth absorbs energy over an area of pi multiplied by (R squared), which is the area 'facing' the sun. The energy is emitted by the Earth over an area of 4 x pi x (R squared), which is the entire surface area of the Earth. A black body at temperature T emits a known amount of energy, E, given by the Stefan-Boltzmann law, E = sigma x (T to the power 4). Sigma is Stefan's constant, equal to 5.67 x (10 ^-8) W (m^-2) (K^-4). Assuming the Earth to be a black body we can equate the absorbed solar flux to the outgoing infra-read energy using Stefan's law:

Energy in = Energy out
(1370 W m^2) x (pi x R^2) = [sigma x T(E)^4] x [4 x pi x R^2]

rearranging gives T(E)^4, therefore T(E) = 279 K.

This is fairly close to the correct surface temperature, but this is because there are two large and compensating errors in the model. To make a better model, the energy absorptive properties of the Earth's atmosphere need to be considered, and the fact that some radiation is reflected back into space by clouds. If we assume 30% of incoming solar radiation is reflected, this alters the calculated surface temperature to 255 K. Allowing for the presence of the Earth's atmosphere and the greenhouse effect gives a surface temperature of 289 K and an atmospheric temperature of 251 K.

I appreciate what you've said about the need for discussion of the subject, but Rickster71's give the impression that these issues are separated from the body of the scientific literature and the IPCC report. Solar forcing of the climate is discussed in Chapter 2 of the IPCC Working Group I fourth assessment report. The explanation for the assigned probability of attributing human activites to the recently observed warming is discussed in chapter 9. The National Research Council reports I referred to earlier were produced by committees of scientists with considerable expertise and experience.
Thanks, tbewick. I understand much, but certainly not all of the math involved. (Math and physics classes at UC Bezerkley were 45 years ago. :eek:) But my primary question still lingers. It is a given that the issue here is not greenhouse gases or "global warming" per se, but is the nascent effect of mankind's industrial activities that contribute some measure of additional warming. What I had hoped to get from your perspective is the significance of that human contribution (both in degrees of temperature and concommitant global meteorogical changes). Thanks.
 
T

tbewick

Senior Audioholic
Hi Tomorrow,

According to what I've read in the IPCC 2001 and 2007 reports, the temperature rise over the 20th century of ~0.7 degrees celsius is thought mainly to be due to human activities. This attribution is a described usually as a signal-to-noise problem, where the natural variability of the climate is the noise and the human activity the signal. When you run climate models to simulate natural variability, ie. things like volcanic eruptions and solar forcing, you end up with there being a net decrease in temperature over the 20th century. If you double the noise level from these model runs or increase it even further, you still end up with a mismatch between the observed warming and the model results. In order to get a response in-line with observations, you need to include the human external forcing. I've a grab (attachment 1) from the technical summary of the IPCC 2007 Working Group I fourth assessment report that hopefully illustrates this.

The effect of temperature changes in relation to increases in greenhouse gases is often spoken of in terms of the climate sensitivity, which is the response of the climate's average temperature to a doubling in carbon dioxide concentration. This is given a best estimate of ~3 degrees celsius in IPCC 2007, with a range from around 1 - 4.5 degrees.

Experts like Richard Lindzen have criticised models as being an inadequate simulation of natural variability, and have also proposed lower climate sensitivities, like 0.6 degrees. On your earlier point of weather forecasts versus long term climate models, I know Roger Pielke Sr has said something on this. He criticised the recent IPCC report for saying that long-term predictions of climate are 'easier' than short-term weather forecasting. I think the thing is that climate models have to do much more simulation of the climate system than weather forecasts, probably making their predictions less precise. The thing is that they can probably to some extent counter this by the temperature predictions being global in scope, which helps to suppress errors due to natural variability at the regional level.

Personally I feel a precautionary approach is worthwhile, because of the large uncertainties of the climate system. For instance, even at low carbon dioxide stabilization levels, the equilibrium temperature response could still be fairly high - around 4 degrees. There are also uncertainties over the responses of carbon sinks, eg. plants may help to suck up more carbon dioxide at low temperature increases but at higher increases they may end up becoming a net carbon emitter. There is similar uncertainty in the future behaviour of the ocean as a carbon sink.

If anyone's interested, I realise that I made a mistake in my first post. The IPCC 4th Assessment Report Working Group II actually selected 29,000 from 80,000 data series for study. Their selection was based on the following criteria: (1) Ending in 1990 or later, (2) spanning a period of at least 20 years; and (3) showing a significant change in either direction, as assessed in individual studies. 89% of the 29,000 observational data series that showed significant change were consistent with the direction of change expected as a response to warming (from the Working Group II Summary for Policymakers).
 
Last edited:
Tomorrow

Tomorrow

Audioholic Ninja
Thanks, tbewick. That's exactly what interested me, and I appreciate your (healthy) scientific skepticism. There is an abundance of the "Sky Is Falling" mentality that seems to be occuring within the media and the political sector that could use a good dose of rationally derived uncertainty.
 

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