a_unique_person
Director of Hatcheries and Conditioning
A metaphor. The natural influences you refer to cannot change the earths climate so quickly. Nothing more, nothing less.
Shermer flips GW stance
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A metaphor. The natural influences you refer to cannot change the earths climate so quickly. Nothing more, nothing less.
Badger
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You seem to speak with a certainty that I don't get from info put out by researchers in this field.
And, yes, vulcanism can change the earth's climate so quickly (Krakatau). It has been postulated that the "little ice age" was caused by a particularly intense period of sunspot activity. That happened pretty quickly too.
AUP, your arguments are not going to convince me of anything. I assume my words will not convince you of anything either.
a_unique_person
Director of Hatcheries and Conditioning
I was talking about the Malkinov cycles, sun spots, etc. It is all discussed in "The Weather Makers". He also explains the rapid shifts, which these could not cause, as due to such exceptional events. Given that there are no expceptional events happening, the normal cyclical events don't explain the temperature rise either.
CapelDodger
Penultimate Amazing
Your post failed to demonstrate any blatant falsity, as I pointed out in my resonse. Linking to a propaganda site ain't gonna do it. Orbital changes affect climate, but not on the timescale we're considering. The solar cycle is too short, El Nino even shorter, volcanic effects shorter still.
Cycles don't just happen, there are mechanisms behind them. You seem to be falling back on belief that "something" unidentified - on a very well-monitored planet - is happening. Appealing to the age of the planet and its natural cycles is no foundation for belief when the recent, very unusual warming is the issue.
CapelDodger
Penultimate Amazing
Or Mt. Pinatubo in 1991, the climate effects of which were measurable, measured, and have since dissipated. Mega-volcanoes will have a slightly longer influence, but we'd have noticed if, say, bits of Yellowstone Park were raining down on New England. The eruptions about 65 million years ago that created the Deccan Flats probably had a greater influence, but they went on over thousands of years and cannot be going on unnoticed in the modern world.
The Little Ice Age has been linked with something called the Maunder Minimum of sunspot activity. Correlation does not imply causation, as I'm sure we'd all agree. The LIA was principally a phaenomenon of the North Atlantic which has been projected onto the global scale - that's Eurocentrism for you. The global influence of reduced insolation in that period was minor. The evidence from the period suggests that the LIA was linked to a weakening of the North Atlantic Drift (and there is a suggested mechanism for that weakening).
You're not going to convince me either, since I've heard it all before and it's deeply unconvincing to anyone well-versed in the subject.
a_unique_person
Director of Hatcheries and Conditioning
That appears to be what typically happens around here.
Badger
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Actually, my post, was in response to your statement that there was only one mechanism. Whether the site is a propaganda site or not, it also identified other mechanisms. The existence of other mechanisms is not propaganda, no matter what your opinion of that particular site is.
I agree with you. Cycles don't just happen. There are mechanisms behind them. Right now, the mechanisms and their interactions are not well understood, and there is no concensus in this field of research yet.
Yet, you think the single mechanism is human generated greenhouse gasses.
I disagree with you that the recent past is very unusual. And this is only because there isn't enough data available yet to support the claim that what we are experiencing is unusual OR the claim that what we are experiencing is merely a normal fluctuation.
What I know for sure is that there isn't a mile of ice on my house at the moment, nor are there vast tropical inland seas at my doorstep. Things have been colder and warmer. We're somewhere in the middle. Maybe, one day I'll know where, and why.
a_unique_person
Director of Hatcheries and Conditioning
Anecdotally, Australia has been experiencing the worst droughts ever. Not just the usual two or three year cycles, but eight years, and some areas turning into permanent desert.
The in depth research is reporting temperature rises, and saying that if it was not for global dimming, (a man made phenomenon), it would be a lot worse.
TobiasTheViking
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So, if no katrinas hit after the hurricane season is over, will you do the same as you require the "Environmental skeptics" to do if some katrinas do hit?
If your answer is no, then how does that not make you a hypocrate.
If your answer is yes, what is the nominal limit at which this means the "Environmental skeptics" are wrong and should admit it. And what is the nominal limit at which you are wrong and should admit it.
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Anacoluthon64
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Carson's book hardly convinced me of anything other than to find out more on the subject. I only mentioned that I'd read the book because it is, as I indicated, widely credited as the seminal work bringing about widespread environmental awareness. Much of what she wrote has indeed been fairly criticised.
I think you are referring to the precession of the Earth's spin axis which has a period of about this length. It's not the average Earth-Sun distance that varies; it's the effective inclination of the Earth's spin axis that changes relative to the plane of the ecliptic. Remember, this inclination accounts for the seasons, so changing the inclination is bound to have an effect on Earth's climate.
'Luthon64
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Badger
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Thanks for getting me to delve into this more.
This http://geography.about.com/od/learnabouttheearth/a/milankovitch.htm covers the variation in the earth's orbit, precession, and the variation in the earth's inclination.
Leads me to the question "where are we now?" What interactions between our nearly circular orbit, inclination of the earth, location of continents and oceans and their relative heat retention and transmission characteristics, sunspot activity, and energy output cycle of the sun are taking place?
I just don't see the GW issue simply as "man's pumping more CO2 into the air, and that's causing everything".
Anacoluthon64
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No worries.
Indeed, which is why the issue has become so contentious in the first place. Other factors that bear upon it are the reduction in capacity of CO2 sinks, such as the Amazon rain forests and oceanic microorganisms, and the potency (about 58 times as effective a greenhouse gas as carbon dioxide for the same mass) and increasing emission of methane from livestock farming and coal production.
'Luthon64
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TobiasTheViking
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sorry, could you point out the two fallacies in "There is good evidence that higher global temperatures will promote a rise of greenhouse gas levels, implying a positive feedback which will increase the effect of anthropogenic emissions on global temperatures."?
a_unique_person
Director of Hatcheries and Conditioning
From "The Weather Makers", p41.
The Milankovich cycles are
1) The elliptical orbit around the sun changes shape over a period of about 100,000 years. This is the eccentricity of the orbit. Sometimes it is more elliptical than others. At present, there is only a six percent difference between January and July in the radiation reaching the earth from the sun. However, at it's most elliptical, the difference is between 20 and 30 percent.
2) The 42,000 year cycle of the earth's tilt on it's axis. This varies between 21.8 and 24.4 degrees. This does not alter the total radiation hitting the earth, but alters where it will fall.
3) The final cycle of 22,000 years is the wobble of the earth on it's axis. When the axis shifts from pointing to the Pole Star to more Vega, the winters will be more cold, the summers more hot.
Only when the continental drift brings the earths land surfaces closer to the Poles, these cycles will cause an ice age. Mild summers and cold winters allow snow to accumulate, until it forms great ice domes.
Even at their most extreme, the cycles only cause a total variation in the energy reaching the earth of less than 1/10 of one percent.
However, this small a variation will cause a temperature rise of 5C.
Such small inputs, or forcings, can cause such huge temperature variations. Computer models cannot simulate an ice age unless the CO2 in the atmosphere is reduced in the Souther hemisphere.
The Milankovich cycles are
1) The elliptical orbit around the sun changes shape over a period of about 100,000 years. This is the eccentricity of the orbit. Sometimes it is more elliptical than others. At present, there is only a six percent difference between January and July in the radiation reaching the earth from the sun. However, at it's most elliptical, the difference is between 20 and 30 percent.
2) The 42,000 year cycle of the earth's tilt on it's axis. This varies between 21.8 and 24.4 degrees. This does not alter the total radiation hitting the earth, but alters where it will fall.
3) The final cycle of 22,000 years is the wobble of the earth on it's axis. When the axis shifts from pointing to the Pole Star to more Vega, the winters will be more cold, the summers more hot.
Only when the continental drift brings the earths land surfaces closer to the Poles, these cycles will cause an ice age. Mild summers and cold winters allow snow to accumulate, until it forms great ice domes.
Even at their most extreme, the cycles only cause a total variation in the energy reaching the earth of less than 1/10 of one percent.
However, this small a variation will cause a temperature rise of 5C.
Such small inputs, or forcings, can cause such huge temperature variations. Computer models cannot simulate an ice age unless the CO2 in the atmosphere is reduced in the Souther hemisphere.
a_unique_person
Director of Hatcheries and Conditioning
Which are?
Hindmost
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I have got a question on the software that is used to analyze the global environment based on using ice cores from the poles or Greenland or other areas of the planet. The design basis of the software on how various events are modeled might help--how does it compare with current weather patterns etc. Anyone have a link or some knowledge.
glenn
glenn
The people at Real Climate talk about validating their models here:
http://www.realclimate.org/index.php?p=100
http://www.realclimate.org/index.php/archives/2005/08/et-tu-lt/
CapelDodger
Penultimate Amazing
The site mentions other influences on climate, which are not in question. Nor are they applicable to the warming of the last century or so, because they do not operate on such a time-scale. The site does not present any mechanism for the current warming. It does get into dissing climate models, for some reason; the connection with the title is a tad obscure.
There is a consensus in the field that greenhouse warming is a major contributor to the current warming. The mechanisms may not be well understood by you, but they are well understood by the scientists involved.
I think the dominant influence is greenhouse warming, which aligns me with the scientific consensus.
There is quite sufficient data to determine that the current warming is very unusual. Nothing similar has been experienced on a global scale in recorded history.
You speak of changes that occur over vast time-scales. The Milankovich cycle, which may explain the ice-age cycle, has a period of about 110,000 years. In 10 or 20,000 years the ice may well be back, kilometres-thick, over New York and old York. That has nothing to tell us about what's going on now.