The summer of 2007 was apocalyptic for Arctic sea ice. The coverage and thickness of sea ice in the Arctic has been declining steadily over the past few decades, but this year the ice lost an area about the size of Texas, reaching its minimum on about the 16th of September. Arctic sea ice seems to me the best and more imminent example of a tipping point in the climate system. A series of talks aimed to explain the reason for the meltdown.
Sea surface temperatures were warmer this past summer also; I forget how many standard deviations the temperature was off the trend, but it was definitely anomalous. The region of the meltback is just inside the Bering Strait, where warm water flows in from the Pacific, but in the analysis of Steele et al. this inflow of comparatively warm water was not particularly anomalous in 2007 relative to other years. It could be that the exposure of the sea surface to the atmosphere by the melting ice could have an impact, although the meltback is so late in the solar heating season (September) that this effect seems of limited explanatory value also. Bit of a chicken and egg problem here.
Melting ice can be seen from space, I believe as puddles sensed by the QuickSCAT satellite. The puddles are most abundant in mid-summer when the sunlight is strongest, and by mid-September when the ice meltback was the strongest, the melting season was largely over. Apparently the reason for the disappearance was an anomalous weather system which generated a strong jet of surface winds blowing straight over the pole southward toward the Atlantic ocean, a “Polar Express”. A research ship frozen into the ice in 2006 crossed the Arctic in about a year, about three times faster than the transit time of the Fram in the 1890’s. To summarize, the ice cubes in the freezer tray didn’t melt because the freezer is broken exactly, but because the ice cube tray fell out of the freezer onto the warm floor.
The disappearance of the ice was set up by warming surface waters and loss of the thicker multi-year ice in favor of thinner single-year ice. But the collapse of ice coverage this year was also something of a random event. This change was much more abrupt than the averaged results of the multiple IPCC AR4 models, but if you look at individual model runs, you can find sudden decreases in ice cover such as this. In the particular model run which looks most like 2007, the ice subsequently recovered somewhat, although never regaining the coverage before the meltback event.
So what is the implication of the meltback, the prognosis for the future? Has the tipping point tipped yet? When ice melts, it allows the surface ocean to begin absorbing sunlight, potentially locking in the ice-free condition. Instead of making his own prognosis, Overland allowed the audience to vote on it. The options were
- A The meltback is permanent
- B Ice coverage will partially recover but continue to decrease
- C The ice would recover to 1980’s levels but then continue to decline over the coming century
Options A and B had significant audience support, while only one brave soul voted for the most conservative option C. No one remarked that the “skeptic” possibility, that Arctic sea ice is not melting back at all, was not even offered or asked for. Climate scientists have moved beyond that.
Re #150
David, if you are talking about La Nina, I don’t think that is suppose to be a condition lasting several years. Notice the quote said “The climate projection, published today in the journal Science, suggests that a natural cooling trend in eastern and southern Pacific ocean waters has kept a lid on warming in recent years.”
Tilo Reber (#148) wrote:
David B. Benson (#150) wrote:
Sounds about right:
Unfortunately, that is about the only thing the article says regarding the lull before the storm. Haven’t been able to find out anything else as of yet.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
Last update: 5 December 2007
“Here we attempt to monitor ENSO by basing the Multivariate ENSO Index (MEI) on the six main observed variables over the tropical Pacific. These six variables are: sea-level pressure (P), zonal (U) and meridional (V) components of the surface wind, sea surface temperature (S), surface air temperature (A), and total cloudiness fraction of the sky (C). These observations have been collected and published in COADS for many years.”
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/ts.gif
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/lanina.gif
“… The 1998-2000 La Niña does not resemble any previous event in this comparison figure. It started late (about three months later than the previous latest case), and it featured a superimposed annual cycle (peaking around May and troughing around November) that does not match the other events…”
…
“The most recent El Niño event of 2006-07 reached a similar peak as the 2002-03 event, but lacked ‘staying power’, and collapsed rather early in 2007….”
Re #146
Thanks for the link David. But it seems that for every opinion there are other opinions. I think it is important to note that more coral reefs grow in warm water than in cold; that coral reefs have risen with the sea level since the last ice age; and that some people believe that bleaching can sometimes be a survivable process whereby one form of algae is swapped for another form of algae that is more capable of dealing with the modified temperature.
In any case, here are some links to use as a contrast to your link.
http://www.theaustralian.news.com.au/story/0,25197,22065659-5006786,00.html
http://www.sciencedaily.com/releases/2007/11/071129183829.htm
http://www.sciencedaily.com/releases/2006/06/060623094718.htm
[Response: The fact that some particular kinds of coral may resist damage from warming does not allow one to conclude that the coral ecosystem will remain healthy in a thriving environment. There are always survivor species — ferns made it through the Permo-Triassic mass extinction, lots of other plants we
live with now almost didn’t. If you read the “related stories” on the sciencedaly dispatch, you’ll get a more balanced view of the magnitude of the problem than you’d get from the distorted spin Mr. Reber puts on it. –raypierre]
Ref 145 Tilo writes “I’m anxious to have the empirical evidence, and the next couple of years just may provide some of it.” Bravo!! I believe the IPCC position is that the ONLY solar effect is a change in TSI. There is so much bias in the media, that a “tipping point” may occur when the general public realize that maybe, just maybe, global temperatures are not going up after all, and certainly not as fast as the proponents of AGW suggest.
Jim Cripwell posts:
[[There is still no sign of rising world temperatures in the 21st century.]]
Unless you actually do the math.
http://members.aol.com/bpl1960/Ball.html
Tilo posts:
[[If it is a weak cycle, then we will get a chance to gather some evidence about the relative strength of solar forcing vs CO2 forcing. If CO2 forcing dominates solar forcing, then we should continue to have temperature go up during this time. If it doesn’t, then we may actually turn around and go down for some period of time – even with the current levels of CO2. I believe that the IPCC position is that CO2 is the driving factor for global warming and solar forcing is too weak to reverse it. There are a few people who disagree with that. I’m anxious to have the empirical evidence, and the ]]
What’s wrong with the past 400 years of empirical evidence? Yes, the sun affects climate, no, it isn’t driving the current warming.
> But it seems that for every opinion there are other opinions.
> — T. Reber, above
“You are entitled to your opinion. But you are not entitled to your own facts.” – Senator Daniel Patrick Moynihan.
Jim Cripwell wrote: “There is still no sign of rising world temperatures in the 21st century.”
If find it very admirable that the moderators and participants on this site who are actually knowledgeable about climate science, rather than being steeped in ideologically-driven denialist sophistry, consistently respond to such baseless assertions with patient, polite, informative comments.
Re #158
“You are entitled to your opinion. But you are not entitled to your own facts.”
I agree completely Hank. But the facts are not always that easily determined. For example, one would think that modern temperature data sets are facts. So on the one hand I can look at RSS and UAH data that is extremely closely correlated, or I can look at GISS data which currently has a bias to the warm side by somewhere between .2 and .3Deg.C, and whose divergence seems to be increasing, when compared to the previous two. Which data set is fact? Or, I can accept the fact that CO2 is a greenhouse gas that contributes to warming; but what is the fact of how much it contributes. James Hansen tells us that it is between 2 and 4 deg C per doubling of CO2. Most of the guys at the Physics forum who have run the numbers; people who have run it through the Modtran software; and others, seem to think that the number is between .7 and 1.5 deg C per doubling of CO2.
Those facts would seem to be important when you are predicting future outcomes. But since they don’t seem to be well nailed down, there is room for opinion.
[Response: This response is exactly what Hank is talking about. Modtran cannot give you climate sensitivity since it doesn’t contain any feedback mechanisms. That is a fact. Thinking is it just a matter of opinion whether it does or not, is just wrong. The ‘fact’ that GISTEMP anomalies have an offset from UAH anomalies is due to a different reference period. It is not a matter of opinion whether that is important (it is not). Etc. By looking into the details of these issues it is possible to determine what is fact and what is opinion, but your reading on these issues is inadequate to the task. You can get pointers on how to do it better from comments here or by reading the technical literature (rather than in a forum), but you need to approach it with an open mind. Good luck. – gavin]
> in the 21st century
But you aren’t claiming that means anything, because you know it’s a capital fault to pick less than all the available information, right? You wouldn’t try to fool us here, would you?
If your banker insisted on showing you only selected months for your retirement money’s returns, you’d squawk, right? You’d want the whole period. Economists warn about this same error often.
Example:
http://www.econbrowser.com/archives/2007/12/ntsds2.gif
RSS UAH is cold lately hey? Well the stratosphere in the Northern Hemisphere is extremely cold, is no coincidence, it is said that this MSU reading is confused with the stratosphere, deja vue boasting!
144-149 The astronomical Arctic sea ice melt of 2007 masks the certain fact that if the winds were Southwards instead of Northwards, 2007 would have been the warmest year in history worldwide, not just for the Northern Hemisphere as it now stands, despite a quiet sun and La Nina. I am quite keen on an official calculation which will state how much Global Temperatures was reduced by this melt.
Tilo Reber posts:
[[James Hansen tells us that it is between 2 and 4 deg C per doubling of CO2. Most of the guys at the Physics forum who have run the numbers; people who have run it through the Modtran software; and others, seem to think that the number is between .7 and 1.5 deg C per doubling of CO2.]]
Sai Tilo, you are comparing doubling CO2 by itself (MODTRAN) to doubling it with water vapor, albedo and other feedbacks (Hansen). They aren’t the same number. Houghton (“Global Warming: The Complete Briefing,” 2004) says the figure is 1.2 K for CO2 alone and 2.5 with feedbacks. I think the IPCC says 1.2 and 2.0-4.5.
Yes, Wayne, that’s an interesting point. We are beginning to get estimates of the amount of ice melt. How much heat went into that, and was it enough to “take the top off” global temperatures?
RE:#155
“I believe the IPCC position is that the ONLY solar effect is a change in TSI.”
There may be something to that Jim. Looking at the chart I’ve linked, (if it’s correct) it shows that the irradiance for the solar lows of the last 50 years is still higher that the irradiance of the solar highs that we achieved in the 19 century. Of course by the same token, the chart may explain much of the warming pattern that we have seen in the 20th century.
http://www.junkscience.com/Greenhouse/irradiance.gif
There may be other factors involved, such as feedback from the rise in TSI. I’m talking way over my head here, but there are some other phemomena that may be playing a part. For example, I have heard that at times there are things that look like magnetic ropes that attach from the sun to the earth, and that energy can flow across these from the sun to the earth. But like I said, I’m way over my head on that. I think Leif Svalgaard is one of the authorities on the subject, if you want to know more.
Ref 156. You will have to do better than that if you are going to convince me. I know no-one on RC will ever agree that world temperatures have stabilized, let alone, horror of horrors, actually decreased. But there are at least four sets of data on average global temperature anomalies; NASA/GISS, NCDC/NOAA, HAD/CRU, and satellite MSU/RSS. These are not well correlated, and the correlations have become poorer in recent years. I have searched, but cannot find any study that compares and contrasts the different methods. If you want to convince me, you need to either produce a study which shows that the NASA/GISS data is undoubtedly the closest to reality, or a strudy which shows that all four sets of data give the same result.
Jim Cripwell writes:
[[ But there are at least four sets of data on average global temperature anomalies; NASA/GISS, NCDC/NOAA, HAD/CRU, and satellite MSU/RSS. These are not well correlated, and the correlations have become poorer in recent years. I have searched, but cannot find any study that compares and contrasts the different methods. If you want to convince me, you need to either produce a study which shows that the NASA/GISS data is undoubtedly the closest to reality, or a strudy which shows that all four sets of data give the same result.]]
Try graphing them all. Ts against time, averaged over 12 months.
The NASA/GISS figures include the poles, which I believe the HAD/CRU doesn’t.
Re #166 (Jim Cripwell) “I know no-one on RC will ever agree that world temperatures have stabilized, let alone, horror of horrors, actually decreased.”
Er, we would if they had, Jim, but unfortunately they haven’t. Even though I don’t enjoy being proved wrong any more than most people, I’d much rather be wrong than right on AGW. Although I’ll probably be dead from natural causes before it causes mass starvation and nuclear war (unless we take prompt and in many ways painful action), my 12 year old son very likely won’t be.
Jim C,
You’re going to have to start posting under a different name or a pseudonym if you’re going to convince anyone here that you can be convinced of anything that doesn’t involve undescribed, unobserved, non-human related factors for which we have no evidence accounting for climate change, (presumably we shouldn’t rule out UFO’s or cattle mutilations). As it is, after myriad occasions of having fatuous solar assertions blown up, you were asked a pretty simple question- describe an experiment whose outcome would count as evidence in support of the theory of AGW in your mind. You answer was so conspicuous a dodge it it’d make Bill Clinton blush. The prosecution rests.
Tilo,
Was that a skeptical argument or a parody of a skeptical argument? It’s getting so they are difficult to tell apart.
Majorajam wrote: “… undescribed, unobserved, non-human related factors for which we have no evidence accounting for climate change, (presumably we shouldn’t rule out UFO’s or cattle mutilations).”
Actually there is a “theory” that extraterrestrials are covertly present on Earth, where disguised as humans they have infiltrated industry and government and manipulated human technologies so as to deliberately raise the levels of carbon dioxide and methane, thereby making the Earth’s atmospheric & oceanic chemistry and climate hospitable to their alien physiology, while at the same time the effects of climate change will decimate the human population over the next century, in preparation for their large-scale invasion and colonization of the Earth.
There is as much evidence for that “theory” as there is for some of the other “theories” offered by the deniers. Plus it has the virtue of explaining why some people, such as oil company executives, are acting as they are: it’s because they aren’t really human.
> magnetic ropes
http://news.yahoo.com/s/afp/scienceastronomyus
“David Sibeck, project scientist at NASA’s Goddard Space Flight center….’We believe that solar wind particles flow in along these ropes, providing energy for geomagnetic storms and auroras,’ he told the annual meeting of the American Geophysical Union.”
We know energy from the Sun gets here. This is a ‘how’ not a ‘more than we knew existed’ report.
ENSO is mistakenly described as a Pacific Ocean phenomenon. The cooling and warming tendency manifests across the entire tropical region in all major oceans as can be seen if one looks at current sea surface temperature anomalies. It is amplified in the Pacific by the northward shift of the west wind drift increasing the volume of water in the Humboldt Current. Ocean temperatures fall in both the western and the Eastern Pacific during a La Nina event. In an El Nino event sea surface temperatures rise in both the East and the West, as they do across all tropical latitudes apparently in response to a widening cloud free atmospheric window.
ENSO phenomena relate strongly to the aa index of geomagnetic activity and are driven by the sun. The last three solar cycles have been El Nino dominant. The next three will be La Nina dominant as the magnetic field of the sun declines. To check this cyclic activity for yourself simply add the monthly values of the SOI for each solar cycle since 1880 and graph the result. The cyclical effect will then manifest.
The biggest response to low latitude temperature change is seen in the northern hemisphere north of Latitude 60°. This is simple stuff. Arctic sea ice will recover shortly. Stop worrying about your carbon footprint. It’s a red herring.
Seems my last post got missed, so I’ll try again…does anyone know why is that the rate of ice sheet melting in Greenland has been accelerating the last 4 years, while the annual temperature in most of Greenland has actually fallen slightly in the same period? Is there a lag, or is it because of hotter/longer summers (despite a slight annual downtrend), or because the temperatures in the more northerly regions (which have increased slightly in the last 4 years) matter more? Or because ice sheet melt is complex and responds to lots of different factors other than surface air temperature?
As a bonus, is there any evidence about rate of ice sheet melt in Greenland in 1930’s which saw similarly warm temperatures?
Thanks in advance.
Dylan, water doesn’t melt from an average summer temperature, it melts from a local daily temperature.
So start where you got your information — where was that? If you’ll give us the source we can help check it out. It may be you’re not getting good information, or the aren’t giving you the footnotes to check the source.
Google Scholar is often helpful; you can limit it to ‘recent’ and even by year. This is a search for articles in Scholar dated 2007 using
summer greenland melt
See what you think:
http://scholar.google.com/scholar?hl=en&lr=&safe=off&scoring=r&q=summer+Greenland+melt&as_ylo=2007
Also, you can then click “Images” and see
http://images.google.com/images?tab=si&sa=N&hl=en&lr=&safe=off&q=summer+Greenland+melt&as_ylo=2007
So, you can see from this that there’s more water melting during the summers. Does that help understand why the glaciers may be moving more?
Look back at the place you got the original information — this is a good chance to practice skepticism. Did they give you enough information to think this through for yourself? If not — glad you asked here.
I’m just an amateur reader here. Whatever I’ve gotten wrong or missed, I expect correction promptly.
Can’t help you with the 1930s, but that’s because I don’t have time to look right now. There weren’t any satellites, lots less info, so it may be harder to say.
First, thanks to Raypierre for giving all of us an eyewitness report of the AGU meeting and all the interesting and sometimes scary science there. Its good for the people who are interested in the science, the public debate about the science, and the political implications of the science to have a window into the scientific community. Second when ptarmigans came up again, I did remember the earlier post. I did a quick google search on Ken Tape to make sure it wasn’t another joke. It wasn’t. Fool me once, shame on you. Fool me twice… ;)
#154 (Tilo Reber) The comments about coral reefs bring up some good points. First the Climate Feedback link David Benson (#146) included was about the recent issue of Science and the review paper on the status of coral reefs. For someone trying to learn about the issue and does not have any background on the science involved, a review paper like the one discussed on Climate Feedback should be given more weight than individual studies like those cited by Tilo Reber.
As someone who does have some scientific training in this area, I think the review paper is a more accurate view of the status of coral reefs because it includes all the threats to coral reefs. You can see the whole picture only when you look at all the pieces.
Hank, my previous post explained where I got the info – from the GISTEMP site, and the GRACE satellite measurements.
You say “water doesn’t melt from an average summer temperature, it melts from a local daily temperature” – but surely, all else being equal, the higher the average temperature over the summer period, the faster water will melt? And as I said, looking at the GISTEMP individual station data on a month by month basis, the summers have in fact been getting hotter over the last 4 years – however colder temperatures in the winter have meant that the annual mean temperature has sloped off slightly in the same period.
It seems logical that only temperatures ABOVE zero matter when considering ice melt, so on the surface this is the best explanation – but like I said, I’m not an expert, and would prefer not to guess.
Re the decline of coral reefs in 175 154 and 146, other stressors include nutrient loading with attendant algae blooms that coat and kill coral polyps, in addition to direct human destruction in the form of cyanide and dynamite fishing.
The idea that the “white desert” of bleached coral reefs will spontaneously resurrect in warmer, more acidic waters, is wishful thinking.
> GISTEMP …
> surely, all else being equal, the higher the
> average temperature over the summer period,
> the faster water will melt?…
> … only temperatures ABOVE zero matter
How many stations are there on the Greenland icecap?
Most of the data I know about comes from the satellites.
The images I pointed to show that information.
Hank, I don’t know – there’s no easy way of determining this. It would be nice if GISTEMP provided a map showing where the stations were.
I’ve tried accessing raw satellite data before, and that was a real pain, if you know of a site that has it available in a user-friendly manner please tell!
This map gives an idea of what land-based measurements are available, and also demonstrates that even summer temperatures have cooled considerably across much of Greenland:
http://data.giss.nasa.gov/cgi-bin/gistemp/do_nmap.py?year_last=2007&month_last=11&sat=4&sst=0&type=trends&mean_gen=0506&year1=2002&year2=2006&base1=1951&base2=1980&radius=250&pol=reg
On that basis, it’s a bit hard to understand what could be driving the faster melt rate.
Re#171
’We believe that solar wind particles flow in along these ropes, providing energy for geomagnetic storms and auroras,’
Thanks Hank. I had lost my link to that one. In any case, my objective was not to say that this phenomena caused global warming, but to point out that there are many factors that play into to global energy equation that we don’t yet fully understand.
The basic features of the newly reformed Arctic Ocean ice make it a new ice world loaded with leads, there is a chance to see them now on this site (http://www.weatheroffice.gc.ca/data/satellite/hrpt_dfo_ir_100.jpg) while it is colder (light winds), sat images are fairly clear, a RADARSAT shot would bring out the real chaotic state though. This is a real changed ice scape, with implications already known through very capable RC contributors, winds bring out heat , no winds allow cooling to take place. Those extra leads are the main characteristic so far.
Actually that link had not just summer, but the whole period May-Oct. If you just look at Jun-Aug, it does show a warming patch in the SE, but still, hardly a consistent pattern. Perhaps if it was filtered to only temperatures above 0, it would be different.
http://data.giss.nasa.gov/cgi-bin/gistemp/do_nmap.py?year_last=2007&month_last=11&sat=4&sst=0&type=trends&mean_gen=0603&year1=2002&year2=2006&base1=1951&base2=1980&radius=250&pol=reg
#179 Dylan,
If you use GISS as you linked to:
http://data.giss.nasa.gov/gistemp/maps/
Set up and make this map.
Land – GISS Analysis,
Ocean – none
Map Type – Trend
Mean Period – Spring March – May
Time interval – 2002-2006 [your time period]
Smoothing – 250km
Projection – Polar
It seems Greenland warms >2degC in the spring.
Like Hank I’m just an amateur, but here’s what I’m thinking, 2 guesses:
a)
The key warming is in the spring. That wets the ice and lowers it’s albedo, so the ice absorbs more sunlight in the summer season. Even if you get a relative cooling of air temperature in the summer the ice has been pre-conditioned and melts more than it would otherwise. Because it’s ice melting on ice, the local air temperature doesn’t rise as much as if it were land or sea being revealed by the melt. This is because the ice melt reveals more ice, and melt water is in constant contact with the ice. It takes as much energy to melt an amount of ice as it does to raise it’s temperature from 0 to 80degC. So that powerful energy sink of an ice environment soaks up absorbed solar energy in melting ice.
b)
Also, here’s a Wiki jgp based on satellite data. http://en.wikipedia.org/wiki/Image:Arctic_Temperature_Trend_1987-2007.jpg
That shows a strong warming over a greater period as measured by satellite. I’m wondering if satellite might make the cooling (which seems to be down to 1 station) appear much less significant. Because if the lower troposhpere MSU trends might be more representative of the temperautes up on the ice sheet (mean altitude about 2100metres). From my reading of the 250km smoothed plots it looks like there are 3 temperature stations. All apparently by the coast, i.e. not at altitude.
Steffen Research Group host the Greenland Climate Network some are at altitude (not always working though). http://cires.colorado.edu/science/groups/steffen/gcnet/
Anyone know when/if Steffen Research Group will update with this years Greenland Melt extent (as they have 2005/2)? http://cires.colorado.edu/science/groups/steffen/
Thanks for that CobblyWorlds. I also received this email from a Norwegian glaciologist:
“Very good that you are interested in what is happening with our polar areas. I think you have lined out many of the possible answers in your message! The Greenland ice sheet is large and indeed the dynamics very complex. Therefore it is difficult to single out one reason for the melting but it is little doubt that the meterological conditions during summer are playing a major role here. It is not only temperatures that are important but also wind, clouds, radiation, albedo….. Albedo is extremely important. Once the surface conidtions have changed from a white highly refelctive surface to a darker melting one it will warm up even faster because a dark surface attracts more solar radiation (heat) that a white one. This is a the most important feedback mechansim for polar areas.
I hope this is helpful information for you.”
On surface melting, changing albedo leading to faster melting,
Steffen was in the news some months ago:
http://cires.colorado.edu/news/press/2007/07-05-15.html
Hansen:
http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_2.pdf
Connolley on what he found lacking in Hansen’s paper:
http://scienceblogs.com/stoat/2007/11/hansen_again.php#comments
Blue ribbon panel considers extreme scenarios; nobody reported this:
http://handle.dtic.mil/100.2/ADA473826
#184 A micro experiment to make this point would be adequate, take two ice cubes, freeze one at -5 C the other at -40 C, place them in the same ambiant air at the same time. Which of the two will melt completely first?
This experiment can be carried on a glacier scale if only core temperatures were taken. Given a winter averaging at -40 C, compared to a winter at
-30 C , how much more would the warmer glacier melt?
A heated report full of tidbits:
http://www.cbsnews.com/stories/2007/12/18/2007/main3629629.shtml
Ref 167 Barton writes “Try graphing them all. Ts against time, averaged over 12 months.”. And in #156 also writes “Unless you actually do the math.” I have taken your advice. I collected the data from 2000 to 2007 for all four sets (NASA/GISS. NCDC/NOAA, HAD/CRU, and MSU/RSS). I assumed the 11 months of 2007 represent the whole year. I used a simple linear least squares regression analysis, starting in 2000, 2001, 2002 and 2003. Starting in 2000, all four sets give positive slopes, meaning rising temperatures. The NASA/GISS set gives positive slopes for all starting years. However, the other three sets, for all starting years 2001, 2002 and 2003 give negative slopes, meaning falling temperatures. It would seem that the NASA/GISS data is significantly different from the other three. It would also seem that the other three data sets indicate that world temperatures are falling in December 2007.
Re # 186 Wayne Davidson: ” take two ice cubes, freeze one at -5 C the other at -40 C, place them in the same ambiant air at the same time. Which of the two will melt completely first?”
I’m not a physicist, and I haven’t done the experiment, but comparing the thermal properties of ice at -5C and -40C suggest to me that the result may not be what you might predict:
Thermal conductivity
-5 C 2.25 W/mK
-40C 2.64 W/mK
Specific Heat
-5C 2.027 kJ/kg/K
-40C 1.818 kj/kg/K
http://www.engineeringtoolbox.com/ice-thermal-properties-d_576.html
Re #188
I would suggest to you that for ice at -40ºC to melt it must first pass through -5ºC.
189-190, I side with Phil, but try the experiment Chuck, there is nothing like tactile impressions.
If you don’t have a freezer that goes down to -40 C, try a different temperature range, the results will be similar.
Jim Cripwell, how many years are you graphing there?
Are you aware of this?
http://scienceblogs.com/stoat/2007/05/the_significance_of_5_year_tre.php#
Re # 190,191 Phil.Fenton and Wayne Davidson’s reponse to my comment (#189)
I agree, while the -40C ice cube starts out warming at a faster rate (due to the greater temperature gradient, as predicted by Newton’s Law), its rate of warming will slow as the temperature gradient is reduced, and when it reaches -5C the other cube will have warmed closer to 0C – sort of a thermal version of Zeno’s Achilles and the Tortoise paradox. But, if you re-read my comment, you will see that I did not say the -40C cube will melt first; I was merely suggesting that the time to melting might not be as different as one might expect based on their starting temperatures.
The converse experiment (which I have done) is to start with identical containers of warm water and cold water, put them in freezer, and see how long it takes them to freeze. Surprisingly, depending on the exact experimental conditions, the warmer water sometimes will freeze more quickly:
http://math.ucr.edu/home/baez/physics/General/hot_water.html
Jim Cripwell writes:
[[the other three sets, for all starting years 2001, 2002 and 2003 give negative slopes, meaning falling temperatures. It would seem that the NASA/GISS data is significantly different from the other three. It would also seem that the other three data sets indicate that world temperatures are falling in December 2007.]]
So you used sample sizes of 6, 5 and 4 years, respectively, to derive your trends.
Forgive me if I’m not impressed.
Jim Cripwell, why don’t you just graph the derivative of the temperature vs time, and then you’ll have an instantaneous measure of what temperature is doing for each second! Uh, don’t bother to keep us posted on that, ‘kay?
Jim, at a minimum you need to average over a full solar cycle to have any validity. Come on; get serious.
Re #183: CW, Xavier Fettweis has some nice Greenland melt graphics, updated through 2006 and including some animations, on his research page. IIRC these are based on a different algorithm and data from Steffen. Xavier has a related paper here.
Could anybody suggest how I can find calculations for the warming effect of sea-ice loss. If, in September, Arctic sea-ice was 30% below the long-term average, how would one calculate the radiative forcings from the reduced albedo? Many thanks!
http://ice-glaces.ec.gc.ca/app/WsvPageDsp.cfm?id=11892&Lang=eng
Check out the Quikscat animation on this page showing the progression of Arctic ice between Sept 7, 2007 and Jan 4, 2008.
Correct me if I’m wrong, but this looks like a major loss of multiyear Arctic ice in last few months…
When 2008 melt season begins, the increase in solar energy being absorbed by the Arctic Ocean will not be negligible.
According to Cyrosphere Today, it looks like the Arctic sea ice level has returned to within 200,000 square miles of the 1978-2000 mean.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.anom.jpg
Specifically, there appears to have been many times in the 1980’s when the ice anomaly was less than it is now. Doe this satisfy condition C? (or at least exclude B and A?)
Also, the southern hemisphere ice anomaly is hugely positive right now. (Far outside the 30 year history.) I know that it’s supposed to warm slowly down there, but this seems a little bit much. Any predictions on what the souther winter will bring?