Arctic Sea ice and Greenland glaciers have been on a slow retreating trend for decades, perhaps centuries (at least since the little ice age). This should not be surprising. First, glaciers all around the world have been steadily retreating since 1800:
Also, the Arctic has been the hot spot of the world over the last 30 years or so:
Increasing far more than global averages:
So the question is not necessarily why Arctic Sea ice continues to retreat – this appears part of a long term trend that in fact pre-dates things like, say, man’s production of substantial amounts of CO2. But the more worrisome question has been, why has this retreat seemed to have accelerated the past several years:
Its hard to fully correlate recent activity with Arctic temperatures. In fact, in the last three or four years (see above) we have seen decreasing Attic temperatures, not increasing ones. But never-the-less, this ice picture is often used as exhibit #1 to prove anthropogenic warming. The "tipping point is near" cry supporters of the theory that Earth’s climate, unlike nearly every other long-term stable natural system, is dominated by positive feedback (and ignoring anecdotal evidence that the Arctic experienced similar melting in the 1930s).
Well, last year, there was some preliminary findings form NASA that said that the unusual low ice pack in 2008 may have been due to shifting wind patterns. Now, Anthony Watts points us to two new studies that both conclude something other than global warming and CO2 may be behind recent ice pack trends in the Arctic.
Observations over the past decades show a rapid acceleration of several outlet glaciers in Greenland and Antarctica1. One of the largest changes is a sudden switch of Jakobshavn Isbræ, a large outlet glacier feeding a deep-ocean fjord on Greenland’s west coast, from slow thickening to rapid thinning2 in 1997, associated with a doubling in glacier velocity3. Suggested explanations for the speed-up of Jakobshavn Isbræ include increased lubrication of the ice-bedrock interface as more meltwater has drained to the glacier bed during recent warmer summers4 and weakening and break-up of the floating ice tongue that buttressed the glacier5. Here we present hydrographic data that show a sudden increase in subsurface ocean temperature in 1997 along the entire west coast of Greenland, suggesting that the changes in Jakobshavn Isbræ were instead triggered by the arrival of relatively warm water originating from the Irminger Sea near Iceland. We trace these oceanic changes back to changes in the atmospheric circulation in the North Atlantic region. We conclude that the prediction of future rapid dynamic responses of other outlet glaciers to climate change will require an improved understanding of the effect of changes in regional ocean and atmosphere circulation on the delivery of warm subsurface waters to the periphery of the ice sheets.
Arctic Sea ice continues to retreat – this appears part of a long term trend that in fact pre-dates things like, say, man’s production of substantial amounts of CO2
Actually, in 1850, the atmospheric concentration of CO2 rose above 285ppm (data, graph) for the first time in perhaps a thousand centuries. This increase in CO2 concentration is unequivocally anthropogenic. So the trend shown in your first image does not predate the rise in atmospheric CO2 concentrations, but is coincident with it.
Any change in temperature up to 1950 is not anthropogenic…the IPCC even agrees with that. And after that we have added less than 12% to the ppm count. The world temp has risen .7 degC in the last 150 yrs. Up until a few yrs ago the oceans were warming (releasing Co2). If you check the real data you will see we are now cooling on land,and sea plus the sea level has started to drop. So many from the AGW crowd need to do their homework and look at the real facts that are everywhere if you bother to look.
Any change in temperature up to 1950 is not anthropogenic…the IPCC even agrees with that
Incorrect. CO2 did not suddenly become a greenhouse gas in 1950.
And after that we have added less than 12% to the ppm count.
I am sure you are trying to imply that 12% is not much. Given that for about ten thousand years until 1850, natural variation was no more than about 2%, 12% is a large change. The temperature rise from a 12% rise in CO2 concentration is climate sensitivity * forcing = 0.75 °C/W/m² * 5.35 ln (1.12) W/m² = 0.45°C.
Up until a few yrs ago the oceans were warming (releasing Co2).
At no point since measurements began have the oceans been a net source of CO2
If you check the real data you will see we are now cooling on land,and sea plus the sea level has started to drop.
It is not possible to claim that ‘we are now cooling’. There is no evidence that the warming trend observed over the last 35 years has changed or reversed. Similarly, although Usain Bolt has yet to break his 100m world record, there is no evidence that he is getting slower at running. Sea level hasn’t dropped.
So many from the AGW crowd need to do their homework and look at the real facts that are everywhere if you bother to look.
Doesn’t look like you did any homework before posting all those incorrect claims.
And I just noticed that you were also wrong about 12%. The actual increase in atmospheric CO2 concentration since 1950 has been ~25 per cent.
I trust that before you post again you will do your homework and look at the real facts that are everywhere if you bother to look.
This question of Phase 1 vs. Phase 2 of 20th-century temperature increases often appears in this blog, but I do not see it raised elsewhere. I tend to believe that GW/Scientist/Steve is right on his description of his camp’s view of this issue. My impression is that the thought of mainline Global Warming Pessimists is that increases in CO2 emissions, emerging with the industrial revolution, have impacted temperatures for over a hundred years. This mainline thought continues to say that the aerosols of the mid-20th century temporarily halted temperature increases which began again around 1979. Of course, there are legitimate questions and issues with this proposition, but I do not believe that it is fair to misstate their position. Request for citation: For those who charge that Global Warming Pessimists see pre-1940 warming to be natural and post-1979 to be man-made, please refer to some papers that hold that view. Also, how about a citation from the other side? – that pre-1940 warming was anthropogenic.
Meanwhile, the Steve’s citation for continued increases in sea levels actually shows decreasing levels for over two years, and some could make a case that the drop has been going on for about five years. Obvious points: (1) 2 to 5 years does not make a climate trend. (2) I reserve the right to be cautious about a 2 millimeter measurement taken by satellite miles away on a surface characterized by waves, tides, and occasional turbulence. And (3) increases in sea levels started long before CO2 emissions were significant, and papers theorizing increasing rates are FAR from convincing.
Also, a comment on CO2 levels: It does not appear that a stable CO2 level for pre-industrial times is a settled science. Apparently, ice-core samples support that view, but Thomas B. van Hoof and others cite research that chemical analysis of leaves of land plants preserved in peat and lake deposits show wide variation in CO2 pre-industrial. I am not sure which side benefits from his research. I trust that Steve would recognize that the coefficients in his climate sensitivity equation are controversial.
Also, how about a citation from the other side? – that pre-1940 warming was anthropogenic – how could it not be? CO2 was rising then, after all. But if you want a paper, how about Callendar’s “The Artificial Production of Carbon Dioxide and Its Influence on Climate” – Quarterly J. Royal Meteorological Society, 1938
actually shows decreasing levels for over two years
I don’t think that statement is tenable. Looking at the last two years I see repeated ups and downs, and I would find it impossible to say, from the data, whether there was any non-zero trend. It’s also easy to find other two year segments in which the trend is not clearly upward. As you say, this is a good indication that two years is not a long enough period from which to derive a trend.
and some could make a case that the drop has been going on for about five years
Only if they took the highest measurement from 2003 and the lowest from 2008 and drew a line between them. Such a case obviously does not stand up to scrutiny.
Also, a comment on CO2 levels: It does not appear that a stable CO2 level for pre-industrial times is a settled science.
Depends what you mean by stable. It’s certainly settled science that concentrations now are higher than they’ve been for a very long time, and that they are higher because of fossil fuel burning.
I trust that Steve would recognize that the coefficients in his climate sensitivity equation are controversial
Controversial? No, that is not an adjective that could reasonably be applied. Each term has an error associated with it, but there is nothing controversial about any part of the equation.
Just another example of blind faith….the temp and sea level graphs clearly show a sustained drop. If You choose to ignore facts you are deluding yourself. Callendar and the others of his period picked a figure out of the air and now the IPCC fudge their models with positive feedback factors that are very controversial(not proven). Recent science suggests a neg feedback, once again do your homework its all out there, and above all keep an open mind.
The PDO and AMO are moving into their cool phases as is the Sun….all indications are pointing to a cooling. Give it a couple more years and the argument is dead. Its obvious that CO2 is a very small player if at all.
There is a new video on youtube called Global Warming Or Global Governance?
In eight parts it gives great inside in the AGW hoax and the politics associated with that.
I find “What is normal” better as it is shorter, Global Warming Or Global Governance? goes more in detail and covers all aspects of AGW hoax I know off.
http://www.youtube.com/watch?v=drfqbdEGi8Q&feature=related
Steve,
Isn’t the gist of the graphs shown in this link
that there was very little anthropogenic forcing prior to 1950? These graphs are from the ICPP.
If you’re interested come see how the hockey stick graphs are faked.
http://noconsensus.wordpress.com/2008/10/11/will-the-real-hockey-stick-please-stand-up/
John M – those graphs plot temperature anomaly, not forcing. Checking the source tells me that the anomalies are defined as being relative to the 1901-1950 average. Hence, between 1901 and 1950 they will be close to zero.
It’s very easy to estimate the CO2 forcing, with the standard equation ΔF = 5.35 ln (C/C0), where C0 is the reference level of CO2. From Law Dome CO2 data, CO0 is about 285ppm. In 1950, the concentration was about 335ppm. Today it’s about 387. So, forcing in 1950 was 0.86 W/m². Forcing today relative to pre-industrial is 1.64 W/m². Comparing the two, you can see that it would be quite wrong to suggest that there was very little anthropogenic forcing prior to 1950.
Thank you, Steve and John M, for responding to my question.
Likely, Steve did not understand my request (which could have been clearer) for a citation on pre-1940 (or pre-1950). I was not looking for a citation that the theory existed pre-1940, but rather an IPCC-type citation that pointed out that warming pre-1940 was just as anthropogenic as post-1979 warming. I believe that John M provides information that enlightens me on the position of several “global-warming optimists” on this blog. When anthropogenic forcings are added to the models, the explanatory power of the models does not increase pre-1950. Natural forcings are just as explanatory for temperature trends in the first phase of 20th century warming as natural plus anthropogenic forcings. Naturally, that conclusion is an eye-ball observation which has limitations.
Lots of information here enabling those who wish to educate themselves with some of the scientific facts and papers, including recent work on mans contribution to CO2.
http://epw.senate.gov/public/index.cfm?FuseAction=Minority.Blogs&ContentRecord_id=84e9e44a-802a-23ad-493a-b35d0842fed8&Issue_id=
Steve
It is true those graphs show anomalies, but they also show model hind-casts with and without anthopogenic forcings. As An Inquirer points out, the pre-1950 model curves with and without anthropogenic forcings are quite similar, indicating to me that the IPCC considers there to be very little non-natural forcing in that time period.
John M – as with the temperature, the output of the models will obviously be scaled so that the 1901-1950 mean is zero, both for the anthropogenic and non-anthropogenic forcing cases. This is so that a meaningful comparison can be made. It does not imply that there was no anthropogenic forcing before 1901-1950. You can see that from the equation I gave, and the Law Dome CO2 data.
By the way, saying ‘the IPCC considers’ is incorrect. The IPCC does not do the considering. It just reports the considering that has been done by others.
An Inquirer – the IPCC’s report makes frequent mention of anthropogenic warming since 1750, since the industrial age, and similar phrases. The idea that CO2 only began to affect the climate in 1950 is something I’ve only ever seen on this blog.
Steve,
Please look again at the graphs in my original link. Please answer this specific question:
Can you tell me why the red curve in the graph labeled “Anthropogenic and Natural Forcing” is so similar to the blue curve in the graph labeled “Natural Forcing Only” prior to 1950?
Looks like my previous comment got dumped. Hope this doesn’t end up being a duplicate.
Steve,
Please look again at the graphs in my original link. Please answer this specific question:
Why does the red curve in the graph labeled “Anthropogenic and Natural Forcings” look so similar to the blue curve in the graph labeled “Natural Forcing Only” prior to 1950?
John M – look more closely. The model output and the observations are all expressed relative to the 1901-1950 average, and so during that period they will all be close to zero. But you can see there are differences. For the non-anthropogenic forcing case, it looks to me like the anomaly during 1901-1950 ranges from -0.2 to 0.1. Models including anthropogenic forcing have a larger range – again, just from inspection, it looks like -0.3 to 0.2.
From the Law Dome data I gave, and the CO2 forcing equation, you can see that CO2 concentrations increased by about 5 per cent between 1901 to 1950, and that that corresponds to a forcing of 0.26 W/m². Climate sensitivity is generally estimated to be 0.75°C/W/m², so that CO2 increase would account for a 0.2°C temperature rise.
So, the simple fact that the graphs plot anomalies relative to 1901-1950 means that they look similar at first glance during that period. But there is a difference, if you look a bit more carefully.
Steve,
I thought this whole discussion was relative to whether CO2 could account for glaciers starting to recede in mid 19th century. If CO2 only led to about 0.2C temperature rise 1900 – 1950, how much could it have increased temperature when glaciers started to recede?
I’m not arguing that there NO effect from CO2. I don’t see how 0.2C can lead to any large climate changes, including glaciers starting to decrease.
0.2 is the change in global mean temperature. There is always polar amplification so the temperature change in the arctic would be larger. And even a small temperature change will make a big difference. A glacier obviously melts at its terminus, so the ice temperature there will be close to 0°C, and a small increase will make it recede.
So Steve,
I just want to make sure there is no misunderstanding.
ANY temperature chance greater than +0.000001C can cause a glacier to recede, and since CO2 can lead to a temperature increase and has gone up since the beginning of the 19th century , all glacier losses since 1800 have to be due to CO2.
Thanks for the education.
John M – no. You’ve missed the point entirely. Your tone makes it obvious that your lack of understanding is a conscious affectation, so there’s really no point me saying anything else.
Great!
Steve,
I went back to the 4th IPCC Report, and looked at FAQ 2.1 Figure 2 from IPCC Working Group I Fourth Assessment Report, 2007.
As you indicated, the IPCC goes back to 1750 to note human influences on climate — the impact did not start with Phase II of 20th Century warming. However, the more I looked at this Figure 2, the more suspicious I have become. The Figure is stating that since 1750, human and natural changes have increased radiative forcing (thereby the temperature, of the Earth) by about 1.6 Watts per square meter, with about 95% of this coming from human activities. That seems to be saying that if not for human activities, we still would be in the Little Ice Age. Something seems to be amiss with a theory that says that climate change is driven by radiative forcing, for the last 260 years it has been humans in the driver’s seat. I come from four generations of farmers, and we have a good handle on what has been the climate we have faced — how that climate has oscillated over the decades, not a monotonic trend accompanied by small variations. Of course, one anecdotal farm does not disprove global trends. But our anecdotes can be repeated thousands — indeed, millions of times. A theory should make sense in light of anecdotes and in light of the global experiences. By saying that 260 years of climate change has been vitually all human-induced, credibility is threatened.
An Inquirer – I’m not sure I quite follow you. Why should something be amiss with a theory that says that climate change is driven by humans? Why should credibility be threatened by the finding that anthropogenic forcings have dominated, and whose credibility is it that is threatened? Remember that that diagram you refer to only shows the net forcing since 1750, and that many of the individual components will have varied significantly during that time. There is no implication in the diagram that there has been a monotonic trend.
Steve,
Over 20 years ago, I was willing to accept the idea that “current” climate change is driven by humans. Development of the human species, impact on land use, and use of fuels have been so widespread that AGW made sense. Now, as I see the developments of the last twenty years, I have begun to wonder. Other factors must be strong enough to offset the human impact — at least in the short run. Now, I am reading AGW literature that says the sun variation has been infinitesimally small over the past century, and Figure 2 from IPCC, 4th Report, says that human contribution has been 20 to 30 times any natural variation since 1750. In other words, we would still be in the Little Ice Age if not for human use of fossil fuel. I have a hard time believing that. It is true that Figure 2 does not say that the impact has been monotonic. However, most of the glacier retreat has been monotonic, and much that retreat took place in the 18th & 19th century. It is hard to believe that humans caused that early retreat of glaciers. It seems far more plausible that our understanding of climate drivers has high degree of uncertainty than to say that variations in climate since 1750 has been human driven whicht is what Figure 2 is saying to me. Climate varied before 1750 (and the retreating glaciers confirm that); it hard to believe that the climate would have gone stable after 1750 if not for anthropogenic impact.
First a couple of misconceptions: no-one has ever said that solar forcing has been infinitesimal. It’s not as large as CO2 forcing, but it’s certainly not infinitesimal. And no-one ever said the climate would have ‘gone stable’ after 1750. The rest of your statement expresses an inability to believe things, with no explanation as to why you find these things hard to believe.
we would still be in the Little Ice Age if not for human use of fossil fuel. I have a hard time believing that – the Little Ice Age was a phenomenon restricted to northern temperate regions. But for the 40% increase in CO2 concentrations, global temperatures would be about 1.5°C lower than they are, but there is no reason to think that local climate variations would not have been substantial.
It is hard to believe that humans caused that early retreat of glaciers – why? Basic physics tells us that an increase in CO2 leads to an increase in temperature. CO2 began rising in the late 18th century.
It seems far more plausible that our understanding of climate drivers has high degree of uncertainty than to say that variations in climate since 1750 has been human driven – why? It is not plausible at all to suggest that you can increase the concentration of a major IR absorber by 40% and not raise the temperature.
Ignoring the soot from the coal that was burned as a significant forcing is foolish.
Thinking that temperatures measured from 1750 are accurate to a meaningful extent is even larger.
The idea that a few factories in Europe in the 1750’s was a significant driver of the world climate is laughable on its face. It asks to ignore great forest fires, volcanic activity, changes in vegetation and land use, and the natural cycles.
And falling back on the little ice age while Mann still pretends there was no prior warming period is so rich in irony.
AGW proves over and over to be just a particularly popular apocalyptic cult.