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Hermit
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World is warmer than it has been for 1200 years
« on: 2006-02-10 18:45:21 » |
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Source: Sydney Morning Herald
Authors: Mike Toner (Atlanta, Georgia)
Dated: 2006-02-11
GLOBAL warming in the past century has been greater than any other shift in the world's climate over the past 1200 years, researchers have reported.
The analysis of data from tree rings, shell fossils, ice cores and temperature measurements from 14 locations on three continents shows that the current warming trend is the most extensive change - warm or cold - since the time of the Vikings.
Reporting their findings in the journal Science, Timothy Osborn and Keith Briffa, climatologists at the University of East Anglia, home to the leading British climate research centre, stop short of blaming the 20th-century warming on industrial emissions or other human factors.
But they say the geographic extent of the warming is more widespread and more pronounced than the one that turned Greenland green 1000 years ago.
Their analyses of tree ring and other climate "proxies" from Europe, Asia and North America show two other pronounced climate shifts during the same period: the Medieval Warm Period from 890 to 1170, and the Little Ice Age, which gripped the northern hemisphere from 1580 to 1850.
The medieval warming, which encouraged the Vikings to settle in previously inhospitable regions of Greenland and Iceland, is sometimes cited by critics of modern global warming theories as evidence that the Earth can experience widespread warming independent of human activity.
"It's good that they [Osborn and Briffa] acknowledge that the last thousand years contained two warm periods with a cold one in between," said Fred Singer, president of the US-based Science Policy Project, which frequently disputes claims of global warming. "But it still doesn't prove that the 20th century was unique."
While the study's temperature measurements go back only to the 1800s, the researchers were able to reconstruct the northern hemisphere's climate back as far as the ninth century.
Researchers correlated records with 14 long-term climate proxies, ranging from shell fossils in Chesapeake Bay in the US to tree rings in Mongolia.
"Both individually and taken as a whole, these reconstructions support the conclusion that it is likely that the late 20th century was the warmest period in the past millennium or longer," Dr Osborn says.
Averaged across the globe, the increase in temperatures is numerically small - about one degree above normal, and about two degrees warmer than during the late 1800s.
The increase, however, has been especially sharp in recent years, with all 10 of the warmest years on record occurring since the mid-1990s.
The warming has been linked to accelerated melting of mountain glaciers and polar ice sheets throughout the world, warmer sea surface temperatures, the earlier arrival of spring in the northern hemisphere and other changes.
Many scientists predict the warming will increase if man-made releases of carbon dioxide and other greenhouse gases are not curbed.
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With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion. - Steven Weinberg, 1999
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Blunderov
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Re:World is warmer than it has been for 1200 years
« Reply #1 on: 2006-02-11 12:16:38 » |
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[Blunderov] The weather really has been rather strange in Jo'burg this Summer; it is rumoured that we are officially experiencing a tropical climate. I can believe it. It has rained just about every day, the atmosphere is warm and humid and there are many strange fungi in the park lately.
The article below is rather sobering. It makes mention at the end of the so called 'global dimming' effect. Ironically, some of the pollution is helping to cool the planet. If stops doing that we are in even worse trouble.
http://news.independent.co.uk/environment/article344690.ece
Global warming: passing the 'tipping point'
Our special investigation reveals that critical rise in world temperatures is now unavoidable
By Michael McCarthy, Environment Editor
Published: 11 February 2006
A crucial global warming "tipping point" for the Earth, highlighted only last week by the British Government, has already been passed, with devastating consequences.
Research commissioned by The Independent reveals that the accumulation of greenhouse gases in the atmosphere has now crossed a threshold, set down by scientists from around the world at a conference in Britain last year, beyond which really dangerous climate change is likely to be unstoppable.
The implication is that some of global warming's worst predicted effects, from destruction of ecosystems to increased hunger and water shortages for billions of people, cannot now be avoided, whatever we do. It gives considerable force to the contention by the green guru Professor James Lovelock, put forward last month in The Independent, that climate change is now past the point of no return.
The danger point we are now firmly on course for is a rise in global mean temperatures to 2 degrees above the level before the Industrial Revolution in the late 18th century.
At the moment, global mean temperatures have risen to about 0.6 degrees above the pre-industrial era - and worrying signs of climate change, such as the rapid melting of the Arctic ice in summer, are already increasingly evident. But a rise to 2 degrees would be far more serious.
By that point it is likely that the Greenland ice sheet will already have begun irreversible melting, threatening the world with a sea-level rise of several metres. Agricultural yields will have started to fall, not only in Africa but also in Europe, the US and Russia, putting up to 200 million more people at risk from hunger, and up to 2.8 billion additional people at risk of water shortages for both drinking and irrigation. The Government's conference on Avoiding Dangerous Climate Change, held at the UK Met Office in Exeter a year ago, highlighted a clear threshold in the accumulation of greenhouse gases such as carbon dioxide (CO2) in the atmosphere, which should not be surpassed if the 2 degree point was to be avoided with "relatively high certainty".
This was for the concentration of CO2 and other gases such as methane and nitrous oxide, taken together in their global warming effect, to stay below 400ppm (parts per million) in CO2 terms - or in the jargon, the "equivalent concentration" of CO2 should remain below that level.
The warning was highlighted in the official report of the Exeter conference, published last week. However, an investigation by The Independent has established that the CO2 equivalent concentration, largely unnoticed by the scientific and political communities, has now risen beyond this threshold.
This number is not a familiar one even among climate researchers, and is not readily available. For example, when we put the question to a very senior climate scientist, he said: "I would think it's definitely over 400 - probably about 420." So we asked one of the world's leading experts on the effects of greenhouse gases on climate, Professor Keith Shine, head of the meteorology department at the University of Reading, to calculate it precisely. Using the latest available figures (for 2004), his calculations show the equivalent concentration of C02, taking in the effects of methane and nitrous oxide at 2004 levels, is now 425ppm. This is made up of CO2 itself, at 379ppm; the global warming effect of the methane in the atmosphere, equivalent to another 40ppm of CO2; and the effect of nitrous oxide, equivalent to another 6ppm of CO2.
The tipping point warned about last week by the Government is already behind us.
"The passing of this threshold is of the most enormous significance," said Tom Burke, a former government adviser on the green issues, now visiting professor at Imperial College London. "It means we have actually entered a new era - the era of dangerous climate change. We have passed the point where we can be confident of staying below the 2 degree rise set as the threshold for danger. What this tells us is that we have already reached the point where our children can no longer count on a safe climate."
The scientist who chaired the Exeter conference, Dennis Tirpak, head of the climate change unit of the OECD in Paris, was even more direct. He said: "This means we will hit 2 degrees [as a global mean temperature rise]."
Professor Burke added: "We have very little time to act now. Governments must stop talking and start spending. We already have the technology to allow us to meet our growing need for energy while keeping a stable climate. We must deploy it now. Doing so will cost less than the Iraq war so we know we can afford it."
The 400ppm threshold is based on a paper given at Exeter by Malte Meinhausen of the Swiss Federal Institute of Technology. Dr Meinhausen reviewed a dozen studies of the probability of exceeding the 2 degrees threshold at different CO2 equivalent levels. Taken together they show that only by remaining above 400 is there a very high chance of not doing so.
Some scientists have been reluctant to talk about the overall global warming effect of all the greenhouses gases taken together, because there is another consideration - the fact that the "aerosol", or band of dust in the atmosphere from industrial pollution, actually reduces the warming.
As Professor Shine stresses, there is enormous uncertainty about the degree to which this is happening, so making calculation of the overall warming effect problematic. However, as James Lovelock points out - and Professor Shine and other scientists accept - in the event of an industrial downturn, the aerosol could fall out of the atmosphere in a matter of weeks, and then the effect of all the greenhouse gases taken together would suddenly be fully felt.
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the.bricoleur
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making sense of change
 
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Re:World is warmer than it has been for 1200 years
« Reply #2 on: 2006-02-13 06:17:21 » |
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I am going to comment on the article posted by Blunderov first; then I will return to comment on the article posted by Hermit when I have the time.
Some general comments:
1) There is absolutely nothing new reported here. No new studies, no new science. Some people got together and issued a report.
2) The idea that there is some kind of "tipping point", a "critical point", a "point of no return", is pseudo-scientific nonsense. We do not understand enough about the climate to identify the timing of such a point if one existed.
3) Here's the very best part, the wackiest part ... first they say " The danger point we are now firmly on course for is a rise in global mean temperatures to 2 degrees above the level before the Industrial Revolution in the late 18th century."
OK, good to know, they're defining exactly what constitutes the critical “point of no return", they're specifying the trigger for the ecological time-bomb -- we need to stay within 2 degrees of the 1750 temperature.
But what this article does not mention is that there are no accurate temperature readings available for the mid 18th century. What? I mean, can you beat that for a bogus call to arms? Can you improve on that as "tipping point of the year"?
The dangerous temperature, the tipping point, the temperature to stay away from, the "critical point of no return", is defined as being exactly two degrees above some unknown temperature ...
I mean, really!
Plus, even if someone picked 2°C as the maximum allowable warming and even if this could only be attained by keeping CO2 at 400 ppm, that would mean we would be committed to about 1.8 already even as we speak (or type), so what's the fuss.
The additional point I'd like to make is that in this debate people (meaning the people who produce such "reports") can apparently no longer differentiate between facts, data, observations, assumptions, projections, computer modelling, conjecture etc. It's all rolled into one and presented by the media as: Reality.
Last year's example was the Pentagon Report, which assumed - just as an illustrative example - that in 2007 a big storm would hit. They could just as well have picked 2003 or 2009 or 2015 - it was arbitrarily picked. But guess what: Everybody jumped on the bandwagon and said the Pentagon is "predicting" a big storm in 2007 (and a subsequent collapse of the NADW formation and ice age). If that weren’t so serious, it would be funny. And the funny part is that none of the media, who are normally so proud of being "investigative" "truth seeking" etc. is picking this up. We are living in the age of disinformation.
Now, to be more specific I will pick up on the “rapid melting of the Arctic ice”.
Quote:At the moment, global mean temperatures have risen to about 0.6 degrees above the pre-industrial era - and worrying signs of climate change, such as the rapid melting of the Arctic ice in summer, are already increasingly evident. But a rise to 2 degrees would be far more serious.
By that point it is likely that the Greenland ice sheet will already have begun irreversible melting, threatening the world with a sea-level rise of several metres.. |
... right.
Well, lets start with some perspective on the question. First, the data. Scientists often start by looking at the reduced anomalies of the data, which show the data less average monthly changes. This is a mistake, because the movement of the average becomes greatly exaggerated. This is particularly true when monthly variations are large. I like to begin by getting a larger picture. With that preamble, here is the data. First, the larger picture as promised:
ARCTIC
ANTARCTIC
SOURCE: Cryosphere Today
These are current images, September 30, 2005, so the recent equinox means the sun's shadow covers about half each hemisphere ... what an awesome planet. White is land ice, purple is sea ice. Approximately minimum sea ice extent in Arctic, maximum in Antarctic.
Next, the historical data for the Arctic sea ice area.:
SOURCE: Cryosphere Today
The scientist's fears seem to revolve around the fact that we just have had the lowest August ice coverage on record. Note, however, that they didn't say that it was the lowest ice coverage on record ... just the lowest August ice coverage. They went on to say that they feared that September would show the lowest as well, and that would make it the lowest year on record. FEAR!!!!
Events, however, seem to have overtaken them. On the right above, if you magnify the same data (the most recent information) - We have already hit bottom on the ice extent for 2005, and started back up. Which makes this, not the most ice-free year on record, nor the second most, but ... 2005 is in a dismal tie for sixth place in a small field of 27 years, out of the medals altogether.
I am becoming increasingly concerned about the number of fearful scientists. Unfortunately, the overwhelming majority of climate science is funded by government, and the competition for funding dollars is intense. Focusing global media attention on the state of the cryosphere is the way to keep funding dollars flowing to where the temperature is cold, so I understand the pressure to spice up plain old boring science with a little dash of fear.
But let's get real. For about a decade (1979-90), minimum ice coverage averaged around 6 million sq. km. Since 1990, minimum ice coverage has averaged around 5.5 million sq. km. This year, last year, the year before that, and the year before that have all been stultifyingly normal, at around 5.5 million sq. km.
This is a "tipping point"? This is a newsworthy event?
And what is this mythical "tipping point" when it's at home? It seems the "tipping point" relates to a postulated feedback, which goes like this:
Quote:| less ice reflecting the sunlight --> more solar absorption --> warmer temperatures --> less ice etc. --> ice free Arctic |
Ref: Global Warming 'Past the Point of No Return' By Steve Connor. The Independent UK. Friday 16 September 2005
Which all sounds very logical, until you realise how little the polar regions are warmed by the sun. Instead, they are warmed by the heat transported from the equator by the atmospheric circulation of the "Hadley Cells". A small difference in the amount of ice coverage at the poles means nothing. It is the heat transferred from the tropics that determines polar temperatures. The minimum in arctic ice in 1998-99, for example, was a result of the 1998 El Nino warming of the tropical Pacific, not ice-reflectivity feedbacks.
Why doesn't the sun matter at the poles? Because at polar latitudes, the sun is always low in the sky. This affects surface heat absorption in three ways. First, the sun intensity per square metre of surface varies as the cosine of the latitude, so at 80º North the sun only has cos(80) = 17% of the energy per surface area it has at the equator.
The second is that as the latitude increases, more and more of the sunlight is reflected off of the surface. The amount absorbed is roughly proportional to the same function as before. So only 17% of the available energy is absorbed by the surface at 80º North, and the rest reflected to space.
Those two alone reduce the absorption of solar energy down to 17% absorbed times 17% intensity = 2.9%. In other words, the surface at 80º North only absorbs 2.9% of the solar energy absorbed at the Equator. But wait, there's more. The sun has to travel further through the atmosphere at the poles than at the equator, so atmospheric absorption is increased and surface absorption is lessened. How much less? Don't know, but we're currently at 3% of the tropical sun, so we'll call it about 2% and let it go at that.
The only reason the poles are not blocks of ice year round is the heat that is exported from the tropics. The idea that a bit more or less sun absorbed by unfrozen ocean at the poles will cause runaway melting is in complete contradiction to thermodynamic reality.
The real problem is the short length of the record, less than 30 years. Conclusions drawn from temperature records less than a hundred years long are notorious for their unreliability. They also lead to spurious claims of "highest on record" and "lowest on record", merely because the record is so short. Here, for example, is what we know about the Arctic temperatures leading to the post-1978 ice loss:
Wow, scary stuff, climate has gone crazy, temperatures are skyrocketing, better buy an air conditioner for the igloo, notify the polar bears ... but wait, news-flash, this just in ...
A sobering dose of reality. Note that from 1935-1945, arctic temperatures were much higher than today, and dropped from that peak until about 1960. This is why all of the scare stories on the arctic including last year's much heralded "Arctic Climate Impact Assessment" (ACIA) start their temperature records in 1960 -- it makes the current situation look catastrophic. Yes, things have gotten warmer since 1960 ... but what the fearful scientists somehow forget to tell you is that temperatures were even warmer before that.
You want radical change, radical warming? From 1920 to 1940, the Arctic temps skyrocketed, warming by +/- 4ºC in two decades ... about twice as much as the current rise since 1960, and in less time, and all without the benefit of CO2 increase. If Greenpeace had been around then, they'd have had to blame it on ... shit, I don't know what they'd blame it on, but they'd be sure it's the fault of humans.
The question is not whether the world is warming. It is whether the warming is natural. I see nothing in the temperature graph of the recent Arctic warming that looks unnatural. From 1880 to 1940, the overall rise in Arctic temperature was steeper, larger, and longer than the current (1965-2004) rise.
To recap thus far, during the period of record 1880-present, Arctic temperatures generally:
- Rose for 60 years, to 1940.
- Fell for 25 years, to 1965.
- Rose for 40 years, to the present.
- Were higher in the 30's and 40's than they are today.
We know that the change in CO2 from 1880 to 1940 was far too small to be the cause of that first prolonged rise, so it must be a natural event. Thus we know for a fact that large, long-duration temperature increases in the Arctic occur naturally. In fact, there is nothing in the current record of Arctic temperatures that we haven't seen even in our pitifully short instrumental record. We've seen longer, warmer, and steeper in just the last century and a half. (I say pitifully short because the climate has cycles that are thousands of years in length.)
In this regard, an interesting study has just been published showing one of the longest continuous series of measured temperatures, taken at Armagh Observatory in Northern Ireland. Here is the data:
This site is of interest because it has maintained one of the longest continuous records of temperature available, and also because it is only about twelve degrees south of the Arctic Circle.
First, look at the overall record. If anomalous, human caused, hockey-stick shaped warming has come to the northern reaches of the earth, somebody forgot to tell the astronomers at Armagh about it. There is absolutely no sign of it in this two-century record. No evidence of unnatural change, no odd variations, just a 0.6 degree per century rise that has been sustained for two centuries.
Note the warm period (red line above linear trend) in the 1940's. This is the same period of worldwide warmth shown in the Arctic data, although it was more pronounced in the Arctic. Like in the Arctic, this was followed by a cooling period (red line below linear trend). The cooling lasted longer in Armagh, until the late 1970's. Since then, it has warmed again, but only at the historical rate.
As I said above, the question is not whether the earth is warming. The question is; is the warming natural or CO2 induced? If it were CO2 induced, we should see signs of increasing warming starting perhaps as early as the 1940s, when fossil fuel use started to become significant. We should also see signs of greatly increased warming since the end of WWII, when fossil fuel use skyrocketed. In particular, if CO2 were having an effect, the temperature rise per decade should be increasing steadily since about 1945 along with the CO2.
In the Armagh records, we see neither of these predicted trends. Long term, the temperature rise has been both steady and gradual. The greatest trend in a single decade was from 1819-1828, a decadal temperature rise that was much larger than any modern rise. Here is the record of the decadal change, with each data point (blue line) showing the temperature trend over the prior ten years:
Note that the variations in the temperature trends were generally larger in the 1800s, with Armagh both warming and cooling at rates of up to nearly two degrees per decade. So there is nothing unusual about the recent temperature rise.
In summary:
- Don't trust short climate records in general, or Arctic climate records that start post 1950 or so.
- The Arctic was warmer in the 1930s than it is today, and somehow, mysteriously and magically, neither the polar bears nor the Inuit became extinct. Nor did we go over any mythical "tipping point".
- There is nothing unusual about the temperature rise of the last decades.
the bricoleur
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Hermit
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Re:World is warmer than it has been for 1200 years
« Reply #3 on: 2006-02-13 09:33:06 » |
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[Hermit] Bricolor, Nicely done. Thanks for taking the time.
[Hermit] Reports of "warming", based on incomplete TS and excluded evidence does not much bother me. Reports re polar bears do concern me - the fossil record shows that they have been around and eating cute seals for at least twice as long as we know we've been walking upright. If they are *truly* drowning en mass then factors other than those raised by you must be at play. Have not had the opportunity to research this as I would like. Comments?
[Hermit] Have you read anything by Dr. Theodor Landscheidt? Despite extreme skepticism on my part on a number of the claims on the latter of the referenced web sites [infra], he was internationally recognised as being remarkably competent at making long term predictions based on solar excursions and was extremely concerned by the projected 2030 Gleissberg minimum. Ref e.g. http://mitosyfraudes.8k.com/Calen/Landscheidt-1.html and
http://www.iceagenow.com/New%20Little%20Ice%20Age.htm
[Hermit] I personally suspect that the Sun's output is almost certainly the largest single variable factor in determining the Earth's surface temperature. We know that the Sun's output also varies over a very wide range. Yet that appears to be the missing factor in any prominent discussions. Why do you think this receives scant attention?
[Hermit] Have some soundbite numbers. One week of the "War against Terror" is worth more money to the USA than all the money spent Internationally on climate and weather research put together. Then too, the US will spend more on "defense" and intelligence (excluding the costs for any real wars - like Iraq and Afghanistan which get their own appropriations) this year than all of the rest of the world. And second only to this military and intelligence spending is the annual catastrophe bill - which keeps rising. I really have to wonder why - outside of lunatic religious ideology - climate, weather, oceanographic and solar research is not worth more money and - possibly - I'd say probably - better investigation - no matter the outcome. It can't possible be worse spent than the current hemorrhaging. How say you? Please try to support your response.
Thanks Hermit
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With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion. - Steven Weinberg, 1999
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Blunderov
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Re:World is warmer than it has been for 1200 years
« Reply #4 on: 2006-02-13 11:29:33 » |
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Quote from: Hermit on 2006-02-13 09:33:06
[Hermit] Bricolor, Nicely done. Thanks for taking the time.
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Yes, thanks from me too. This much is clear to me; we need to know a lot more about what is going on, so the Hermit's point about the apportionment of funds is very salient.
From my layman's point of view, there do seem to be grounds for concern. Our local weather is different than it's ever been in my 40 + yrs experience. And intuitively, it seems likely that gases added to the atmosphere must have some effect.
Looking forward to more.
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Hermit
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Re:World is warmer than it has been for 1200 years
« Reply #5 on: 2006-02-13 13:34:18 » |
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And the first thing I heard from the Hermitess on walking through the door (found by googling by name):
Russian scientist predicts 'mini Ice Age'
A Russian astronomer has predicted that Earth will experience a "mini Ice Age" in the middle of this century, caused by low solar activity.
Source: PhyOrg.Com
Dated: 2006-02-07
Khabibullo Abdusamatov of the Pulkovo Astronomic Observatory in St. Petersburg said Monday that temperatures will begin falling six or seven years from now, when global warming caused by increased solar activity in the 20th century reaches its peak, RIA Novosti reported.
The coldest period will occur 15 to 20 years after a major solar output decline between 2035 and 2045, Abdusamatov said.
Dramatic changes in the earth's surface temperatures are an ordinary phenomenon, not an anomaly, he said, and result from variations in the sun's energy output and ultraviolet radiation.
The Northern Hemisphere's most recent cool-down period occurred between 1645 and 1705. The resulting period, known as the Little Ice Age, left canals in the Netherlands frozen solid and forced people in Greenland to abandon their houses to glaciers, the scientist said.
I would read this together with the following from a peer reviewed introductory level paper I found on the U.S. Global Change Research Information Office website (site recommended by me as being as reliable as this black art appears to get and with remarkably good external peer reviews). This paper might go someway to resolving The Bricoleur's apparent mystification about "tipping point's". Another important factor here is the use of a model which relies primarily on the ocean currents rather than air to transfer heat - a model which I find very persuasive not only because water can carry and store much more heat than the atmosphere, but also because these models have provided numerous relatively good independent predictions (and as is usual in this field where the experts can't yet agree on whether we are getting hotter, colder or staying the same, a slew of less good predictions) of historic data which were a serious obstacle to their acceptance until very recent and ongoing work on ice-cores showed that the rapidity of climate change as reflected in deep ice-cores (notice the date) matched oceanographic thermal transfer models far better than the primarily atmospheric models.
Potential for abrupt transitions
It has long been thought that the great Ice Ages came and went on time scales measured in thousands of years, and less momentous changes--such as the Holocene Maximum or the Little Ice Age--over the span of several centuries. Current studies and more recent paleodata have revealed quite another face of the climate system, called "abrupt transitions," in which major shifts in some components of the Earth's climate are accomplished on time scales of decades or less.
Initially proposed, and later verified, was the revolutionary notion that the large-scale circulation in the North Atlantic could persist in one of two patterns, or states, both of which were quite stable, with the possibility of abrupt switching between the two. In the first, the warm Gulf Stream that flows along the eastern coast of the U.S. continues northward, reaching beyond the British Isles to the Norwegian Sea, ameliorating the climate of northwest Europe. James Joyce aptly referred to this condition in Ulysses, when he wrote that "All Ireland is washed by the Gulf Stream."
In the other possible mode, the northward extension of the Gulf Stream is weakened by a reduction in the salinity of surface waters in high latitude regions of the North Atlantic. With less salt, seawater is not as dense, and is less able to sink during normal wintertime cooling. Restricting the ability of the North Atlantic to circulate water downward limits the amount flowing in from the warm Gulf Stream. The result of this "short-circuit" in ocean circulation is a much cooler climate for all who live downstream, including Northern Europe.
The surprising evidence from the paleoclimate record is how quickly the switch between warm and cold states can be accomplished. Evidence from ice-age portions of recent Greenland ice cores suggests that changes of this sort may have taken place in the past in the span of five to ten years. These abrupt transitions are most likely linked to an increase in the release of icebergs from continental glaciers, which on melting contribute large volumes of freshwater into the ocean, systematically reducing the local salinity.
Whatever the cause, we now know that in at least the North Atlantic the climate system can change very rapidly. Might ocean circulation change as rapidly in the future, perhaps as a consequence of other significant changes in the system? The answer is "maybe." There are no permanent ice sheets today on the North American continent, as was the case in the past, but melting of Arctic sea ice or the extensive Greenland ice cap could well influence ocean salinities. Increased precipitation over the North Atlantic, induced by warmer temperatures, could also reduce the saltiness of seawater, short- circuiting the ocean circulation in a manner similar to what occurred during the ice ages. In fact, greenhouse models call for such a change in precipitation, and the present rate of warming in the subpolar North Atlantic--less than what is recorded in the rest of the world--is also in agreement with what should happen as a result of an altered state of ocean circulation. A test of the models is whether the slower warming of the subpolar North Atlantic will persist.
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With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion. - Steven Weinberg, 1999
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rhinoceros
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My point is ...
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Re:World is warmer than it has been for 1200 years
« Reply #6 on: 2006-02-14 21:46:27 » |
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Quote: quote: Iolo Morganwg
quote:less ice reflecting the sunlight --> more solar absorption --> warmer temperatures --> less ice etc. --> ice free Arctic
Ref:Global Warming 'Past the Point of No Return' By Steve Connor. The Independent UK. Friday 16 September 2005
Which all sounds very logical, until you realise how little the polar regions are warmed by the sun. Instead, they are warmed by the heat transported from the equator by the atmospheric circulation of the "Hadley Cells". |
Of course heat transport is very important. We wouldn't be talking about anthropogenic climate change at the poles otherwise, would we? We would just blame the sun. However, don't the months of polar day make any difference compared to the months of polar night?
The question is "how small is small", in calories absorbed, and how it works.
Quote: quote: Iolo Morganwg
A small difference in the amount of ice coverage at the poles means nothing. It is the heat transferred from the tropics that determines polar temperatures. The minimum in arctic ice in 1998-99, for example, was a result of the 1998 El Nino warming of the tropical Pacific, not ice-reflectivity feedbacks. |
As I read it, the argument in the article is that the effect is triggered when the reflectivity (albedo) of the ice decreases because too much ice has melted for any reason, and then the melted ice absorbs more and more heat.
Quote: quote: Iolo Morganwg
Why doesn't the sun matter at the poles? Because at polar latitudes, the sun is always low in the sky. This affects surface heat absorption in three ways. First, the sun intensity per square metre of surface varies as the cosine of the latitude, so at 80? North the sun only has cos(80) = 17% of the energy per surface area it has at the equator.
The second is that as the latitude increases, more and more of the sunlight is reflected off of the surface. The amount absorbed is roughly proportional to the same function as before. So only 17% of the available energy is absorbed by the surface at 80? North, and the rest reflected to space.
Those two alone reduce the absorption of solar energy down to 17% absorbed times 17% intensity = 2.9%. In other words, the surface at 80? North only absorbs 2.9% of the solar energy absorbed at the Equator. But wait, there's more. The sun has to travel further through the atmosphere at the poles than at the equator, so atmospheric absorption is increased and surface absorption is lessened. How much less? Don't know, but we're currently at 3% of the tropical sun, so we'll call it about 2% and let it go at that. |
So it seems. I'd say that 17% x 17% is about right, the first one because of the angle and the second one because the sunlight has to travel a longer path in the atmosphere; the second one contains the "weakening" of the sunlight. And to this, we have to factor-in the albedo -- how much heat the ice absorbs. To be more realistic, we might want to add the secondary radiation from clouds and staff that hangs in the air. Of course it's still small. Isn't it freezing cold up there?
Quote: quote: Iolo Morganwg
The only reason the poles are not blocks of ice year round is the heat that is exported from the tropics. The idea that a bit more or less sun absorbed by unfrozen ocean at the poles will cause runaway melting is in complete contradiction to thermodynamic reality. |
The argument in the article is that when ice melts (as a result of something else) its reflectivity changes, so it absorbs more sunlight, and the cycle goes on. I can see your calculation and your comparison to the thermal transport, but how does it addresses this argument.
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Re:World is warmer than it has been for 1200 years
« Reply #7 on: 2006-05-12 00:59:29 » |
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Climate change evidence stronger: scientist
[Hermit: The following seems in-line with the Polar Bear and Migratory Bird reports I have been following recently. Notice the huge range of sea level rise predictions. From significant but not insurmountable at 9cm* to catastrophic disaster at 88cm. I wonder when better data will become available? After the floods?
*We know that the 20th century saw an 8" rise over US coasts without seeing a catastrophe. We have also been reminded of what class iii and iv hurricanes can do to cities and people. Now consider that Katrina wasn't even a class v "Hurricane" nor even a 100 year storm. It was a class iv, 50 year, 150 mph hurrican when it trashed New Orleans. Given that wind energy increases with the cube of wind velocity, a 100 year class v could be much worse. Especially if the seas were higher before the storm started.]
Source: Reuters
Authors: Gerard Wynn
Dated: 2006-05-11
COLOGNE, Germany (Reuters) - Global temperatures may be increasing more quickly than first thought, and evidence is stronger that humans are causing the rise, the World Bank's Chief Scientist Robert Watson told Reuters on Thursday.
Scientists widely accept that climate change is happening and could cause more extreme weather, global warming and rising sea levels.
But the scale of change and its cause are hotly contested, as blocs of countries including Europe and the United States are split on how quickly the world should act.
The U.N.-founded group, the International Panel on Climate Change (IPCC), has prepared its fourth report, at draft stage and due for publication in 2007, on the case for climate change, and finds that evidence has hardened, Watson said.
The IPCC's research work is split into working groups, with scientific evidence delegated to Working Group 1.
"Everybody I've talked to in Working Group 1 says the evidence (for climate change) is getting stronger, that this is more and more solid ... and (evidence) that most observed warming is due to human activities," said Watson, who is former chairman of the IPCC.
The third report in 2001 spoke of "new and stronger evidence" that human activities were warming the globe, in turn stronger than the previous report in 1995, which described a balance of evidence suggesting discernible human influence.
Citing most recent, and not necessarily IPCC research, Watson also found a consensus emerging that an expected rise in world temperatures by 2100 compared to 1990 was at the upper end of previous estimates.
"The latest climate change models suggest changes on the upper end of the scale, a projected temperature increase of 3 to 5 degrees."
"The third IPCC report predicted a temperature rise of a 1.4 to 5.8 degrees centigrade increase. This is a global average, increases on land are higher than in oceans, and over polar regions highest of all."
The third IPCC report's estimate translated into a sea level rise of 9-88 cm by 2100, so any higher temperature rise would be bad news to anyone living by the sea.
Watson was speaking after telling a carbon trade fair in Cologne that the global carbon market could reach $100 billion per year, as countries increasingly sought to buy pollution cuts overseas to help them meet their domestic targets.
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With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion. - Steven Weinberg, 1999
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Re:World is warmer than it has been for 1200 years
« Reply #8 on: 2006-05-23 12:53:56 » |
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Earth-solar cycle spurs greenhouse gases -studies
[Hermit: I'm no longer able to find a peer reviewed earth-sciences resource of any significance that does not accept the reality of the phenomenon of a recently warmer earth. I am becoming highly skeptical about the few voices left saying "nonsense," primarily because things which are well documented as having been stable for very long periods, seem to have destabilised recently. I refer to, e.g. drowning polar bears, the incredible shrinking summer polar ice cap (20% smaller than 1979), rapidly increasing (double the planetary average rate of increase) arctic temperatures, the Akademik Fyodorov, becoming the first ship to reach the North Pole without requiring an icebreaker in 2005-08. I'm still not sure that the climatologists have absolutely proven causation, as regards "greenhouse gases", but accept that ice core and ocean floor sediment studies have proved at least correlation without doubt.
An en passant American note is that the Republican Government has been removing funds for maintaining and ensuring access to environmental and climate resources and has severely cut the budget for research and weather monitoring. The sad spectacle of salivating democrats simultaneously supporting the slashing of these budgets and demanding further cuts while keeping their heads in the sand over the implications (bleak), yet still supporting wars the stupendous silliness of which is only exceeded by their costs is even more frightening. And now, just in time for the new tornado season, peer reviewed support for higher than estimated temperature increase and consequent worsening of storms.]
Source: Reuters
Authors: Deborah Zabarenko
Dated: 2006-05-22
Greenhouse gases are known to spur global warming, but scientists said on Monday that global warming in turn spurs greenhouse gas emissions -- which means Earth could get hotter faster than climate models predict.
Two scientific teams, one in Europe and another in California, reached the same basic conclusion: when Earth has warmed up in the past, due to the sun's natural cycles, more greenhouse gases have been spewed into the atmosphere.
As greenhouse gas levels rose, so did Earth's temperature, the scientists reported.
Earth has not endlessly warmed up, though, because these natural solar cycles ended, letting the planet cool down and prompting a corresponding drop in greenhouse gas emissions, the scientists reported.
But these previous periods of heating and cooling were not influenced by the burning of fossil fuels, and the current resulting trend toward higher global average temperatures, according to Margaret Torn of Lawrence Berkeley National Laboratory.
"It means the warming is happening faster, each decade is actually warming faster than it would have," Torn said in a telephone interview. "It's the pace of change that will be one of the big problems. It's how humans adapt and the cost that will depend on the rate of change of climate."
KEEPING THE HEAT IN
Global warming is caused in part by the emission of greenhouse gases, including carbon dioxide and methane. These gases are emitted naturally but are also the result of the burning of fossil fuels, especially coal and petroleum products. These gases swaddle Earth in a layer that lets the sun's warmth in but does not allow it to easily escape.
Over the past 30 years, Earth has warmed by 1.08 degrees Fahrenheit (0.6 degrees Celsius), NASA has reported. Over the past 100 years, it has warmed by 1.44 degrees F (0.8 degrees C), indicating a recent acceleration in warmth.
Current climate models predict temperature increases of 2.7 to 8.1 degrees F (1.5 to 4.5 degrees C), but Torn's team found that additional carbon dioxide caused by the natural solar cycle could push those estimates higher.
Taking this into account could mean temperature increases of 2.9 to 11 degrees F (1.6 to 6 degrees C), the scientists said. The higher temperatures are more likely, they said in a statement.
The European team estimated that global warming in the next century may be 15 percent to 78 percent higher than current estimates because these predictions fail to take into account the feedback mechanism involving carbon dioxide emissions.
Both articles are to be published on Friday in Geophysical Research Letters.
Separately, a group of leading U.S.-based scientists whose research has linked global warming with an increase in hurricane intensity warned on Monday that humans must reduce their contribution by developing cleaner energy and transportation or bear the risk of stronger storms.
Last year's extraordinary hurricane season caused about $55 billion of insured losses, and estimates of the total damage range as high as $200 billion, said Dr. Evan Mills, a staff scientist at the Lawrence Berkeley National Laboratory.
"One is faced with repeating history, of putting up with $200 billion worth of damage every so often," said Dr. Peter Webster, a professor at the Georgia Institute of Technology and author of a study last year that found the average strength and duration of hurricanes has doubled in the last 50 years.
"I'm not sure how many $200 billion the country can afford," he said in a conference call with journalists.
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With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion. - Steven Weinberg, 1999
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Re:World is warmer than it has been for 1200 years
« Reply #9 on: 2006-06-23 05:55:10 » |
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Earth warms to 2,000-year high
Studies back evidence that human activities affect global warming and produce hurricanes.
Source: Associated Press
Authors: John Heilprin
Dated: 2006-06-23
Links:
The Earth is running a slight fever from greenhouse gases, after having a relatively stable temperatures for 2,000 years.
The National Academy of Sciences, after reconstructing global average surface temperatures for the past two millennia, said Thursday the data are "additional supporting evidence that human activities are responsible for much of the recent warming."
Other new research showed that global warming produced about half of the extra hurricane-fueled warmth in the North Atlantic in 2005, and natural cycles were a minor factor, according to Kevin Trenberth and Dennis Shea of the National Center for Atmospheric Research, a research lab sponsored by the National Science Foundation and universities.
The Bush administration has maintained that the threat from global warming is not severe enough to warrant new pollution controls that the White House says would have cost 5 million Americans their jobs.
The academy had been asked to report to Congress on how researchers drew conclusions about the Earth's climate going back thousands of years, before data was available from modern scientific instruments. The academy convened a panel of 12 climate experts, chaired by Gerald North, a geosciences professor at Texas A&M University, to look at the "proxy" evidence before then, such as tree rings, marine and lake sediments and glaciers.
Combining that information gave the panel "a high level of confidence that the last few decades of the 20th century were warmer than any comparable period in the last 400 years," the panel wrote. It said the "recent warmth is unprecedented for at least the last 400 years and potentially the last several millennia," though it was relatively warm around the year 1000 followed by a "Little Ice Age" from about 1500 to 1850.
Their conclusions were meant to address, and they lent credibility to, a well-known graphic among climate researchers -- a "hockey-stick" chart that climate scientists Michael Mann, Raymond Bradley and Malcolm Hughes created in the late 1990s to show the Northern Hemisphere was the warmest it has been in 2,000 years.
It had compared the sharp curve of the hockey blade to the recent uptick in temperatures -- a 1 degree rise in global average surface temperatures in the Northern Hemisphere during the 20th century -- and the stick's long shaft to centuries of previous climate stability.
That research is "likely" true and is supported by more recent data, said John "Mike" Wallace, an atmospheric sciences professor at the University of Washington and a panel member.
The academy panel said it had less confidence in the evidence of temperatures before 1600.
But it considered the evidence reliable enough to conclude there were sharp spikes in carbon dioxide and methane, the two major "greenhouse" gases blamed for trapping heat in the atmosphere, beginning in the 20th century, after remaining fairly level for 12,000 years.
The National Academy of Sciences is a private organization chartered by Congress to advise the government of scientific matters.
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With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion. - Steven Weinberg, 1999
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