No, I think we would have expected the slight cooling trend to continue as it has for the last 8,000 years while we easily adjusted to the very slow change until it finally reaches a tipping point into the next ice age. From what I've read that's somewhere between 5,000 and 25,000 years from now. Plenty of time to prepare. But if "On the effect of a new grand minimum of solar activity on the future climate on Earth" (Feulner & Rahmstorf 2010) are right we've already prevented the next ice age. If global warming continues as expected (assuming human emissions continue as they have) then we're in for some pretty drastic and costly adjustments for our civilization.
I just discovered the site a couple of weeks ago. It's hard to take it all in one sitting.
Yes, PIOMAS is a computer model that's been criticized. But the observations from Cryosat come pretty close to matching it which gives us more confidence in the model.
The higher insolation at the beginning of the Holocene was because of orbital variations, AKA Milankovitch Cycles. The condition of the cycles is different now and trending toward cooler. That's why temperatures have been on a slight cooling trend since the Holocene Climatic Optimum about 8,000 years ago. The abrupt warming we are experiencing today has different causes than orbital variation and so we might expect some of the effects to be different.
You mean the CO2 level increases that lag behind the temperature rises?
Congratulations. You know that increased levels of CO2 are a feedback of increased temperatures (primarily from the ocean warming and outgassing CO2). Now show how increasing CO2 by other means than the feedback method doesn't force additional warming.
I think you're doing what a lot of people do. You see the dire predictions but you don't pay that much attention to the time frame attached to them. After having been burned a few times myself I learned better. Yes, some of the predictions are hyperbolic but many of them are proceeding on schedule. The ozone layer, acid rain and Y2K are all things we took action on to mitigate the problem.
You're probably right. What the hoi polloi don't realize is that in the long run global warming is probably going to make all those other things that much more difficult.
You are right. In one of the groups publishing extent measurements any area of the ocean that is 30% covered by ice is counted as extent. That is why area and volume are more informative measurements of sea ice. Both of those are at record lows as well.
You are absolutely right. Volume and area are more telling than extent but as you say extent's the easiest to measure and volume the most difficult. With the launch of Cryosat in April 2010 volume measurements are much more accurate now. That page I cited has graphs for extent, area and volume.
I think we have good enough records to say unequivocally this is the lowest sea ice in several hundred years. Proxies from boreholes drilled in the Arctic Ocean indicate it's the lowest for several thousand years. Here's a paper I referenced in a reply above about Arctic sea ice for the past 47 Ma.
That's the way it usually works. You get a dramatic year followed by more normal years but a bit lower than the previous normal years. Then you get another dramatic year. Meanwhile on average it just keeps going downhill.
Arctic sea-ice extent and volume are declining rapidly. Several studies project that the Arctic Ocean may become seasonally ice-free by the year 2040 or even earlier. Putting this into perspective requires information on the history of Arctic sea-ice conditions through the geologic past. This information can be provided by proxy records from the Arctic Ocean floor and from the surrounding coasts. Although existing records are far from complete, they indicate that sea ice became a feature of the Arctic by 47 Ma, following a pronounced decline in atmospheric pCO2 after the Paleocene–Eocene Thermal Optimum, and consistently covered at least part of the Arctic Ocean for no less than the last 13–14 million years. Ice was apparently most wide-spread during the last 2–3 million years, in accordance with Earth’s overall cooler climate. Nevertheless, episodes of considerably reduced sea ice or even seasonally ice-free conditions occurred during warmer periods linked to orbital variations. The last low-ice event related to orbital forcing (high insolation) was in the early Holocene, after which the northern high latitudes cooled overall, with some superimposed shorter-term (multidecadal to millennial-scale) and lower-magnitude variability. The current reduction in Arctic ice cover started in the late19th century, consistent with the rapidly warming climate, and became very pronounced over the last three decades. This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities. 2010 Elsevier Ltd. All rights reserved
Sure, after it thaws out, then dries out, and assuming it's far enough above the current sea level to remain dry on sea level stops rising. So maybe in a couple hundred years.
Not only air temperature but water temperature also has an effect on ice melt. With less ice the exposed water has more chance to absorb heat and warm up which may delay the start of freezing.
I'll admit I didn't read your link until now. But I don't think it supports your thesis much. To quote from the link:
“Due to this indirect effect, the solar cycle does not impact hemispherically averaged temperatures, but only leads to regional temperature anomalies,” said Stephan Pfahl, a co-author of the study who is now at the Institute for Atmospheric and Climate Science in Zurich.
The authors show that this change in atmospheric circulation leads to cooling in parts of Central Europe but warming in other European countries, such as Iceland. So, sunspots don’t necessarily cool the entire globe – their cooling effect is more localized, Sirocko said.
And...
Moreover, the researchers also point out that, despite Central Europe’s prospect to suffer colder winters every 11 years or so, the average temperature of those winters is increasing and has been for the past three decades. As one piece of evidence of that warming, the Rhine River has not frozen over since 1963. Sirocko said such warming results, in part, from climate change.
The 11 year solar cycle is well known and can be detected in the temperature record. Nobody is denying the effect. But over longer time periods the Sun's cycles average out and since the 1950's the Sun's average output has if anything declined slightly. Yet temperatures are rising.
Sunspot levels which are a pretty good proxy for solar output have been recorded for around 400 years so we have more than 50 years of data. Other proxies that are less certain take the record back even further.
I was 16 at the time. I still remember going outside after watching the broadcast and staring up at the Moon in wonder. I went outside tonight and looked at the Moon and it brought tears to my eyes. Godspeed Neil Armstrong.
The way to neutralize the effect of cosmic radiation is to bury the base in regolith or even tunnel under the surface. And oxygen is not a problem on the Moon. There is plenty of oxygen waiting to be liberated from from moon rocks.
At the same time sequestering 1 gigaton of CO2 a year as in the proposal is a drop in the bucket compared to the approximately 30 gigatons currently emitted by humans yearly. It's not that helpful unless we reduce emissions below 1 Gt and even then the reduction will be slow compared to the rate we've increased CO2. And you are right, those deposits of dry ice will have to be maintained essentially forever to keep the benefit. The plan just doesn't seem that practical to me.
We are saying that the observed variations in the Sun's output in the last 50+ years have had a negligible impact on the Earth's temperature. But we still know that the Sun is essentially the only* source of energy driving the Earth's temperatures and any significant change in the Sun's output would be reflected on Earth.
* The other sources of energy are so small relative to the Sun that they can be ignored in first order calculations.
I wasn't saying I agreed with the decision, just that there is an legal precedent now. I think if Nevada's "None of the above" option had some teeth in it the judge probably would have let it stand. Instead even if NOTA wins in Nevada the guy who gets the most votes gets the office so it has the same effect as a voter simply not voting on that race.
Slashdot Mirror
No, I think we would have expected the slight cooling trend to continue as it has for the last 8,000 years while we easily adjusted to the very slow change until it finally reaches a tipping point into the next ice age. From what I've read that's somewhere between 5,000 and 25,000 years from now. Plenty of time to prepare. But if "On the effect of a new grand minimum of solar activity on the future climate on Earth" (Feulner & Rahmstorf 2010) are right we've already prevented the next ice age. If global warming continues as expected (assuming human emissions continue as they have) then we're in for some pretty drastic and costly adjustments for our civilization.
I just discovered the site a couple of weeks ago. It's hard to take it all in one sitting.
Yes, PIOMAS is a computer model that's been criticized. But the observations from Cryosat come pretty close to matching it which gives us more confidence in the model.
The higher insolation at the beginning of the Holocene was because of orbital variations, AKA Milankovitch Cycles. The condition of the cycles is different now and trending toward cooler. That's why temperatures have been on a slight cooling trend since the Holocene Climatic Optimum about 8,000 years ago. The abrupt warming we are experiencing today has different causes than orbital variation and so we might expect some of the effects to be different.
You mean the CO2 level increases that lag behind the temperature rises?
Congratulations. You know that increased levels of CO2 are a feedback of increased temperatures (primarily from the ocean warming and outgassing CO2). Now show how increasing CO2 by other means than the feedback method doesn't force additional warming.
I think you're doing what a lot of people do. You see the dire predictions but you don't pay that much attention to the time frame attached to them. After having been burned a few times myself I learned better. Yes, some of the predictions are hyperbolic but many of them are proceeding on schedule. The ozone layer, acid rain and Y2K are all things we took action on to mitigate the problem.
You're probably right. What the hoi polloi don't realize is that in the long run global warming is probably going to make all those other things that much more difficult.
AC is one of the oldest posters on /.. So old he doesn't even have an ID number.
You are right. In one of the groups publishing extent measurements any area of the ocean that is 30% covered by ice is counted as extent. That is why area and volume are more informative measurements of sea ice. Both of those are at record lows as well.
You are absolutely right. Volume and area are more telling than extent but as you say extent's the easiest to measure and volume the most difficult. With the launch of Cryosat in April 2010 volume measurements are much more accurate now. That page I cited has graphs for extent, area and volume.
I think we have good enough records to say unequivocally this is the lowest sea ice in several hundred years. Proxies from boreholes drilled in the Arctic Ocean indicate it's the lowest for several thousand years. Here's a paper I referenced in a reply above about Arctic sea ice for the past 47 Ma.
That's the way it usually works. You get a dramatic year followed by more normal years but a bit lower than the previous normal years. Then you get another dramatic year. Meanwhile on average it just keeps going downhill.
If you're interested in graphs here's a bunch more.
Here's a paper about Arctic sea ice for the past 47 million years: "History of sea ice in the Arctic" (Polyak, et. al. 2010). It may have some of the information you seek. Here's the abstract:
Arctic sea-ice extent and volume are declining rapidly. Several studies project that the Arctic Ocean may become seasonally ice-free by the year 2040 or even earlier. Putting this into perspective requires information on the history of Arctic sea-ice conditions through the geologic past. This information can be provided by proxy records from the Arctic Ocean floor and from the surrounding coasts. Although existing records are far from complete, they indicate that sea ice became a feature of the Arctic by 47 Ma, following a pronounced decline in atmospheric pCO2 after the Paleocene–Eocene Thermal Optimum, and consistently covered at least part of the Arctic Ocean for no less than the last 13–14 million years. Ice was apparently most wide-spread during the last 2–3 million years, in accordance with Earth’s overall cooler climate. Nevertheless, episodes of considerably reduced sea ice or even seasonally ice-free conditions occurred during warmer periods linked to orbital variations. The last low-ice event related to orbital forcing (high insolation) was in the early Holocene, after which the northern high latitudes cooled overall, with some superimposed shorter-term (multidecadal to millennial-scale) and lower-magnitude variability. The current reduction in Arctic ice cover started in the late19th century, consistent with the rapidly warming climate, and became very pronounced over the last three decades. This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities. 2010 Elsevier Ltd. All rights reserved
I think you forgot the /sarcasm tag.
Is that you Todd Akin?
Sure, after it thaws out, then dries out, and assuming it's far enough above the current sea level to remain dry on sea level stops rising. So maybe in a couple hundred years.
Not only air temperature but water temperature also has an effect on ice melt. With less ice the exposed water has more chance to absorb heat and warm up which may delay the start of freezing.
I'll admit I didn't read your link until now. But I don't think it supports your thesis much. To quote from the link:
“Due to this indirect effect, the solar cycle does not impact hemispherically averaged temperatures, but only leads to regional temperature anomalies,” said Stephan Pfahl, a co-author of the study who is now at the Institute for Atmospheric and Climate Science in Zurich.
The authors show that this change in atmospheric circulation leads to cooling in parts of Central Europe but warming in other European countries, such as Iceland. So, sunspots don’t necessarily cool the entire globe – their cooling effect is more localized, Sirocko said.
And ...
Moreover, the researchers also point out that, despite Central Europe’s prospect to suffer colder winters every 11 years or so, the average temperature of those winters is increasing and has been for the past three decades. As one piece of evidence of that warming, the Rhine River has not frozen over since 1963. Sirocko said such warming results, in part, from climate change.
The 11 year solar cycle is well known and can be detected in the temperature record. Nobody is denying the effect. But over longer time periods the Sun's cycles average out and since the 1950's the Sun's average output has if anything declined slightly. Yet temperatures are rising.
Sunspot levels which are a pretty good proxy for solar output have been recorded for around 400 years so we have more than 50 years of data. Other proxies that are less certain take the record back even further.
That's not a problem that presenting a picture ID at the polls will solve.
I was 16 at the time. I still remember going outside after watching the broadcast and staring up at the Moon in wonder. I went outside tonight and looked at the Moon and it brought tears to my eyes. Godspeed Neil Armstrong.
Wouldn't the proper term for a citizen of the Luna be a "loonie"?
The way to neutralize the effect of cosmic radiation is to bury the base in regolith or even tunnel under the surface. And oxygen is not a problem on the Moon. There is plenty of oxygen waiting to be liberated from from moon rocks.
At the same time sequestering 1 gigaton of CO2 a year as in the proposal is a drop in the bucket compared to the approximately 30 gigatons currently emitted by humans yearly. It's not that helpful unless we reduce emissions below 1 Gt and even then the reduction will be slow compared to the rate we've increased CO2. And you are right, those deposits of dry ice will have to be maintained essentially forever to keep the benefit. The plan just doesn't seem that practical to me.
We are saying that the observed variations in the Sun's output in the last 50+ years have had a negligible impact on the Earth's temperature. But we still know that the Sun is essentially the only* source of energy driving the Earth's temperatures and any significant change in the Sun's output would be reflected on Earth.
* The other sources of energy are so small relative to the Sun that they can be ignored in first order calculations.
Including contraceptives in a plan probably reduces an insurance companies costs. They're much cheaper than pregnancy.
I wasn't saying I agreed with the decision, just that there is an legal precedent now. I think if Nevada's "None of the above" option had some teeth in it the judge probably would have let it stand. Instead even if NOTA wins in Nevada the guy who gets the most votes gets the office so it has the same effect as a voter simply not voting on that race.