The last time there might have been a "snowball Earth" was long before the dinosaurs died and in fact before the Cambrian explosion around 550 million years ago.
... especially when I question the accuracy being good enough to catch half a degree 100 years ago.
I see this all the time. People assume that just because the precision that the measurements were taken at in the past is somewhat less than it is today that it's invalid to express the aggregation of many of those measurements to a greater precision. This can be statistically shown to be wrong but perhaps the simplest example I can give is this. In baseball a player's batting average is commonly expressed to three decimal places and yet each measurement is a binary choice, either they got a hit (1) or they made an out (0)*. If you said the statistical aggregation of a players batting average had to be expressed to the precision of the measurement then all batters are batting 0.000 (or 1.000 if they miraculously manage to bat better than 0.500). The same principle applies to all areas where statistics are being applied.
*Things like walks or "hit by pitch" don't count in the batting average.
The change in temperature from the height of the last glaciation (around 25,000 years ago) to the Holocene is only about +4 Kelvins. The difference between the height of the Little Ice Age and now only about 1 Kelvin. The increase from 1880 to now is about 0.8 Kelvin. It doesn't take a lot of temperature change to cause some pretty drastic changes from a human point of view.
(BTW, being the pedant I am I have to say Kelvin's don't have degrees even though they are the same size as a Celcius degree. Kelvins are an absolute measurement based on absolute zero.)
To call it positive is premature. Some rebound is to be expected after last years record low and if you let the changes from one year to the next to drive your optimism rather than say something like a 5 or 10 year running mean you're going to get bounced around a lot.
In the case of Pluto it was absolutely because of its orbit which is very eccentric for a planet. Pluto relatively recently (Sept 5, 1989) passed perihelion where is passed inside of the orbit of Neptune and now is headed back out.
If there is a strong upward trend in Arctic sea ice extent, area and volume still going on in 2020 I'll start to think "Hmm... what's going on?" but at this point I have no reason to think that's likely to happen. I kind of regret saying "2014 or 2015" as it probably takes a decade of upward trends for me to change my mind. If you look at the graph referenced you notice that 2013 is above the trend line so I expect 2014 will most likely be a bit lower than this year.
The 2007 "prediction" was one scientist saying "At this rate the Arctic could be ice free in 2013." He didn't say he thought that rate would continue, just what would happen if it did. I'm not aware of any other cryologists that agreed with him.
Perhaps you could put some meat on your hypothesis that sea ice extent oscillates between the poles. But in reality there is little or no connection between the two. The situations are quite different, the Arctic being an ocean surrounded by land whereas the Antarctic is a continent surrounded by ocean.
There are some explanations for the increase in Antarctic sea ice. One part of it is that the winds that circle Antarctica have strengthened, possibly related to the ozone hole over the continent. This tends to open up polynas that create more areas of open water to freeze. Another part is that changes in currents and greater precipitation due to global warming conspires to put fresher water at the surface which makes it easier to freeze. What is not true is that Antarctic sea ice is increasing because it's getting colder. That is demonstrably false.
And as your picture shows the august 2013 Arctic sea ice extent may be 60% higher than 2012 but it's still lower than any year before 2007. As the AC below posts it's a regression to the mean. Wake me up if 2014 and 2015 are higher still.
Water vapor is not an issue since any excess in the atmosphere will quickly condense out to rebalance the level. It's impossible for water vapor to build up in the atmosphere in the way CO2 does.
I'm not convinced that methane from cattle is that big an issue either. Methane has a half life of around 10 years in the atmosphere and will eventually oxidize to CO2 and water. The carbon in the methane that cows belch came from the atmosphere in the first place so it has no effect on the total carbon in the active carbon cycle which is the real issue.
"About half the events reveal evidence that human-caused change was a factor", they say. How big a factor? And the other half revealed no such evidence? It's as though this report was carefully calculated not to change anyone's mind.
Attribution like this is difficult and a relatively new area of study. It's most likely just an honest expression of the researchers level of knowledge. If it advances the field of climate attribution then it was worthwhile. I seriously doubt they even gave a thought to changing anyone's mind in the larger climate change debate.
Not even the most extreme estimates of sea rise produce anything like you say within centuries.
If the West Antarctic Ice Sheet were to collapse it could lead to 10 feet or more of sea level rise in a decade or two. It is mostly grounded below sea level so if it starts to go the disintegration can be rapid There is evidence in the paleo-record of sea level of multiple foot sea level rises on decadal time scales so it appears similar events have happened in the past.. The possibility of this actually happening is unknown at this time but it can't be ruled out.
Personally, I wonder why, if another 1C increase would start a feedback causing temperatures to rise another 20C, why we don't see this happen on parts of the planet that are already 1C hotter than average. It's an average, so there are places that are far above and far below that average. Why aren't we seeing cases of mini-global-warming where, for example, some part of Arizona, due to high humidity (which has many times the greenhouse effect of CO2), enters this deadly feedback mode causing the temperature to rise to 150 only to be saved by nightfall?
I think you fundamentally misunderstand what global warming/anthropogenic climate change means. Very few scientists think it means runaway warming or even 20C rises (unless we continue BAU for another century). The changes are subtle (especially over short time periods) but profound. Perhaps the most obvious example of this is the loss of land based ice from warming and the sea level rise that results. From year to year or even over a decade the rise in sea level is not alarming. But it will take several hundred years for the major ice sheets on Greenland and Antarctica to reach a new equilibrium point with the new temperature. The last time CO2 levels in the atmosphere were as high as they are now sea level was around 70 feet higher than it is today so it wouldn't surprise me if that much SLR is already locked in. It will just take time to manifest.
The only realistic solution to global warming is to bring greenhouse gas emissions, particularly CO2, down to a net zero level. Anything else is just window dressing.
I stand corrected. Thanks for that information about the equatorial sides of the desert zones shifting away from the Equator. The first part of my answer still stands though. The zone edges are moving poleward. This is not good news for Southern Europe and the US Southwest.
That's a popular meme but it doesn't hold much water. Most of the CFC refrigerants were patented in the 1930's so the patents ran out in the 1950's. There was a DuPont patent on a manufacturing process for Freon that ran out in 1979 but the patent for the current refrigerant of choice, R-410 is held by Honeywell (Allied Signal got the patent in 1991) so it doesn't help DuPont.
One thing that has exacerbated that is the length of the warm season has grown enough in some places that the pine beetles are now able to have two generations in a year which has the effect of increasing their numbers far beyond what was seen in the past.
That's true but the soil in the Canadian prairie provinces still usually isn't as good as that found in the US Midwest. It was scraped pretty thin during the last glaciation while the Midwest continued to build up soil since it wasn't covered by ice all that time.
Most deserts around the world are situated in the subtropical zones where the dry air from the Hadley cells descends, around 30 degrees north and south. Global warming appears to be expanding the Hadley cells somewhat which will move the desertified zones a little further toward the poles without necessarily shifting the other edges of those zones further from the equator thus expanding the desert area. For example there is evidence that southern Europe is getting drier but the southern edge of the Sahara Desert shows no signs of shifting northward.
Good lord, the thermal mass of cities and the heat energy produced by human energy production have nothing to do with global warming. The Sun puts as much energy down on the planet in less than an hour than humans use/produce in a whole year.
The complexities of sea level is a fascinating subject. Ocean currents and prevailing winds can cause the water to pile up higher in places that it would otherwise be. The gravitational attraction of the Antarctic ice sheet causes sea level to be higher for thousands of miles around the continent than it would otherwise be. IIRC it's about 20 feet higher along the coast of Antarctica. More here.
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The last time there might have been a "snowball Earth" was long before the dinosaurs died and in fact before the Cambrian explosion around 550 million years ago.
... especially when I question the accuracy being good enough to catch half a degree 100 years ago.
I see this all the time. People assume that just because the precision that the measurements were taken at in the past is somewhat less than it is today that it's invalid to express the aggregation of many of those measurements to a greater precision. This can be statistically shown to be wrong but perhaps the simplest example I can give is this. In baseball a player's batting average is commonly expressed to three decimal places and yet each measurement is a binary choice, either they got a hit (1) or they made an out (0)*. If you said the statistical aggregation of a players batting average had to be expressed to the precision of the measurement then all batters are batting 0.000 (or 1.000 if they miraculously manage to bat better than 0.500). The same principle applies to all areas where statistics are being applied.
*Things like walks or "hit by pitch" don't count in the batting average.
The change in temperature from the height of the last glaciation (around 25,000 years ago) to the Holocene is only about +4 Kelvins. The difference between the height of the Little Ice Age and now only about 1 Kelvin. The increase from 1880 to now is about 0.8 Kelvin. It doesn't take a lot of temperature change to cause some pretty drastic changes from a human point of view.
(BTW, being the pedant I am I have to say Kelvin's don't have degrees even though they are the same size as a Celcius degree. Kelvins are an absolute measurement based on absolute zero.)
In the game of life Mother Nature bats last.
To call it positive is premature. Some rebound is to be expected after last years record low and if you let the changes from one year to the next to drive your optimism rather than say something like a 5 or 10 year running mean you're going to get bounced around a lot.
In the case of Pluto it was absolutely because of its orbit which is very eccentric for a planet. Pluto relatively recently (Sept 5, 1989) passed perihelion where is passed inside of the orbit of Neptune and now is headed back out.
If there is a strong upward trend in Arctic sea ice extent, area and volume still going on in 2020 I'll start to think "Hmm... what's going on?" but at this point I have no reason to think that's likely to happen. I kind of regret saying "2014 or 2015" as it probably takes a decade of upward trends for me to change my mind. If you look at the graph referenced you notice that 2013 is above the trend line so I expect 2014 will most likely be a bit lower than this year.
The 2007 "prediction" was one scientist saying "At this rate the Arctic could be ice free in 2013." He didn't say he thought that rate would continue, just what would happen if it did. I'm not aware of any other cryologists that agreed with him.
Perhaps you could put some meat on your hypothesis that sea ice extent oscillates between the poles. But in reality there is little or no connection between the two. The situations are quite different, the Arctic being an ocean surrounded by land whereas the Antarctic is a continent surrounded by ocean.
There are some explanations for the increase in Antarctic sea ice. One part of it is that the winds that circle Antarctica have strengthened, possibly related to the ozone hole over the continent. This tends to open up polynas that create more areas of open water to freeze. Another part is that changes in currents and greater precipitation due to global warming conspires to put fresher water at the surface which makes it easier to freeze. What is not true is that Antarctic sea ice is increasing because it's getting colder. That is demonstrably false.
And as your picture shows the august 2013 Arctic sea ice extent may be 60% higher than 2012 but it's still lower than any year before 2007. As the AC below posts it's a regression to the mean. Wake me up if 2014 and 2015 are higher still.
Water vapor is not an issue since any excess in the atmosphere will quickly condense out to rebalance the level. It's impossible for water vapor to build up in the atmosphere in the way CO2 does.
I'm not convinced that methane from cattle is that big an issue either. Methane has a half life of around 10 years in the atmosphere and will eventually oxidize to CO2 and water. The carbon in the methane that cows belch came from the atmosphere in the first place so it has no effect on the total carbon in the active carbon cycle which is the real issue.
"About half the events reveal evidence that human-caused change was a factor", they say. How big a factor? And the other half revealed no such evidence? It's as though this report was carefully calculated not to change anyone's mind.
Attribution like this is difficult and a relatively new area of study. It's most likely just an honest expression of the researchers level of knowledge. If it advances the field of climate attribution then it was worthwhile. I seriously doubt they even gave a thought to changing anyone's mind in the larger climate change debate.
Not even the most extreme estimates of sea rise produce anything like you say within centuries.
If the West Antarctic Ice Sheet were to collapse it could lead to 10 feet or more of sea level rise in a decade or two. It is mostly grounded below sea level so if it starts to go the disintegration can be rapid There is evidence in the paleo-record of sea level of multiple foot sea level rises on decadal time scales so it appears similar events have happened in the past.. The possibility of this actually happening is unknown at this time but it can't be ruled out.
Those bumps in the temp record are mostly linked to natural variation. The influence of CO2 shows up in the long term temperature trends.
Not only that but the graph you cite is only for one site in central Greenland, a poor analog for global temperatures.
Personally, I wonder why, if another 1C increase would start a feedback causing temperatures to rise another 20C, why we don't see this happen on parts of the planet that are already 1C hotter than average. It's an average, so there are places that are far above and far below that average. Why aren't we seeing cases of mini-global-warming where, for example, some part of Arizona, due to high humidity (which has many times the greenhouse effect of CO2), enters this deadly feedback mode causing the temperature to rise to 150 only to be saved by nightfall?
I think you fundamentally misunderstand what global warming/anthropogenic climate change means. Very few scientists think it means runaway warming or even 20C rises (unless we continue BAU for another century). The changes are subtle (especially over short time periods) but profound. Perhaps the most obvious example of this is the loss of land based ice from warming and the sea level rise that results. From year to year or even over a decade the rise in sea level is not alarming. But it will take several hundred years for the major ice sheets on Greenland and Antarctica to reach a new equilibrium point with the new temperature. The last time CO2 levels in the atmosphere were as high as they are now sea level was around 70 feet higher than it is today so it wouldn't surprise me if that much SLR is already locked in. It will just take time to manifest.
The only realistic solution to global warming is to bring greenhouse gas emissions, particularly CO2, down to a net zero level. Anything else is just window dressing.
I stand corrected. Thanks for that information about the equatorial sides of the desert zones shifting away from the Equator. The first part of my answer still stands though. The zone edges are moving poleward. This is not good news for Southern Europe and the US Southwest.
That's a popular meme but it doesn't hold much water. Most of the CFC refrigerants were patented in the 1930's so the patents ran out in the 1950's. There was a DuPont patent on a manufacturing process for Freon that ran out in 1979 but the patent for the current refrigerant of choice, R-410 is held by Honeywell (Allied Signal got the patent in 1991) so it doesn't help DuPont.
One thing that has exacerbated that is the length of the warm season has grown enough in some places that the pine beetles are now able to have two generations in a year which has the effect of increasing their numbers far beyond what was seen in the past.
About the only thing that large numbers of countries have been able to cooperate on are thing that are of fairly immediate and mutual benefit.
We did manage to do something about the ozone layer eating chlorofluorocarbons.
That's true but the soil in the Canadian prairie provinces still usually isn't as good as that found in the US Midwest. It was scraped pretty thin during the last glaciation while the Midwest continued to build up soil since it wasn't covered by ice all that time.
Most deserts around the world are situated in the subtropical zones where the dry air from the Hadley cells descends, around 30 degrees north and south. Global warming appears to be expanding the Hadley cells somewhat which will move the desertified zones a little further toward the poles without necessarily shifting the other edges of those zones further from the equator thus expanding the desert area. For example there is evidence that southern Europe is getting drier but the southern edge of the Sahara Desert shows no signs of shifting northward.
The problem with that idea is that it will also cut down on sunlight reaching the surface and thus reduce plant growth and agricultural output.
Everybody's saying the sea will rise 3 feet in short order, ...
Yeah, if you're talking about short order on geological time scales. On human scales it's more like a possibility in a long lifetime.
Good lord, the thermal mass of cities and the heat energy produced by human energy production have nothing to do with global warming. The Sun puts as much energy down on the planet in less than an hour than humans use/produce in a whole year.
The complexities of sea level is a fascinating subject. Ocean currents and prevailing winds can cause the water to pile up higher in places that it would otherwise be. The gravitational attraction of the Antarctic ice sheet causes sea level to be higher for thousands of miles around the continent than it would otherwise be. IIRC it's about 20 feet higher along the coast of Antarctica. More here.
You would think all the hot air would be up lifting...
Good one, I am stealing that line.