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I had posted a while ago about what the carrying capacity of the planet and received an industrial cartesian well thought out answer. I would argue that natural systems don't function in a zero sum game. It is possible to heal the earth and feed ourselves (all of us) and reduce carbon emmissions. Mechanization is not the answer because it reduces efficiency in real terms. It is all about consciousness, humility and understanding our role amoung the other spieces on the planet.
Michale Pollan has done a better job of articulating the solution than I had done at that time. He describes in detail the ecological farming system used by Joel Salatin whom Chris M has interviewed. If you want to cut to the chase start the clip below at the 10 minute mark, though I think the whole thing is worth listening to.
Its not a technological problem that we face, its a change of consciousness. We know what we need to do to solve our problems, It's just a matter of rolling up our sleeves and getting it done. I think the most important way to make this happen is to lead by example. We have to be the cahnge that we want to see.
A botanist friend who has been studying evolutionary dynamics for a while claims that new species are evolving faster than old species have been going extinct. I don't know how to think about that. Could it be that new species are emerging in response to climate change?
Doug
Personally, I would doubt the claim of your botanist friend, Doug. At the rate we destroy and modify existing habitat, I don't think evolution could keep up.
As I understand it, evolution theory predicts about 1 extinction per million species per year. I would assume a roughly similar rate of new species. However, estimates of the extinction rate start at 100 times that background rate.
Tony
Mark,
I would think that you would take some comfort in the fact that ocean surface temperatures have taken 135 years to rise 0.6C. That says that the earth is responding to our CO2 in a low sensitivity fashion. In fact, despite the IPCC models' factor of 4 positive feedbacks, the earth is actually responding in essentially a zero net feedback way. Do you have any reason other than the obviously flawed IPCC models as a basis for believing that it is going to be worse in the next 135 years?
We have been over this territory before. See my post #573. You can cherry pick as many line segments as you wish, but in actual fact, sea level rose at a rate of 3 mm/yr in the intervals 1855-1895, 1940-1970 and about 1990 to present. However, the rate of rise has decelerated to about 2.5 mm/yr for the last decade. See my post #571. So ho-hum. Just why is this alarming now? Shouldn't it have been equally alarming in 1895 and 1970? If we can't cope with one foot per century, then we deserve to drown.
Stan
Interestingly enough the idea of the slow evolutionary change brought on by continuous mutations in the gene pool has been disproven. The fossil record shows quite the opposite, species go unchanged for millions of years and then suddenly at a sudden event millions of new species suddenly appear. The new theory, called punctuated equilibrium tries to preserve the earlier theory of evolution I feel quite unsuccessfully. I am not a creatationist by any means, but there is lots of room for new exploration of "the origin of species". I would be interested to hear any theoies your friend is kicking around. We may be at or near another such event with all that is going on, perhaps mankind is the new asteroid of past earth history.
I have been following the articles about energy and environmental issues put out by the Canadian Ecologist Paul Chefurka for a few years now. This is his latest assessment of our climate change predicament. J.
http://www.facebook.com/Bodhisantra/posts/10151362945723824
According to this article from Real Climate, last year, sea level rise has been accelerating for a long time, though the rate of acceleration has varied a lot and recent (last 30-40 years) rates are difficult to compute due to high level of uncertainty in the data. This chart of corrected data appears in the article:
Interestingly enough the idea of the slow evolutionary change brought on by continuous mutations in the gene pool has been disproven. The fossil record shows quite the opposite, species go unchanged for millions of years and then suddenly at a sudden event millions of new species suddenly appear. The new theory, called punctuated equilibrium tries to preserve the earlier theory of evolution I feel quite unsuccessfully. I am not a creatationist by any means, but there is lots of room for new exploration of "the origin of species". I would be interested to hear any theoies your friend is kicking around. We may be at or near another such event with all that is going on, perhaps mankind is the new asteroid of past earth history.
My friend is not an expert in genetics, he is currently learning from those who are. His specific classification is as a taxonomist, but of the old school. There are a number of plants named after him, but he is blown away by what the geneticists are doing to the old biological classification systems. It's all being turned upside down.
I have long been a bit skeptical of the extinction event we are supposedly in now. They seem to be extrapolating mostly based on habitat destruction or the wave of amphibian disappearances in the last couple decades. But, they identify very few actual species becoming extinct. That may be because they are extrapolating from estimated numbers of species based on what they think ought to be the concentration and diversity of species out there. IOW, there's a lot of guess work going on here.
But, what do I know. I'm still frustrated that I can't ID common trees in my neighborhood from bark patterns or twigs.
Doug
Tony,
If one takes that 0.06 mm/yr^2 acceleration shown at the end of your graph for 1970 and assumes that things remained at least that bad for the next 22 years, that would add 0.06x22 = 1.3 mm/yr to the 1.9 mm/yr that Mark was showing for 1970 (see his post #721). That would get the rate of sea level rise up to 3.2 mm/yr by 1990, in fair agreement with the 3.4 mm/yr shown below for the 1990s. But look at what has happened since then. It has been decelerating by about 0.05 mm/yr^2 for the past decade, thereby lowering the rate of rise to 2.5 mm/yr since 2001. How about extending your graph to about 2005 and putting that negative .05 mm/yr^2 on it and then reconsider what you should say about it.
Stan
Stan,
Note that the graph I posted showed acceleration when measured from the year on the x axis. As I mentioned, the data since the 60s is far too uncertain to state anything about acceleration when measured from the years from then until now. From Mark's chart, however, the actual sea level rise trend appears to be increasing.
Tony
Anyone who has read very many of the things that I have posted on this thread would know that I have a strong preference for real world data over climate model calculations. I also have a preference for plain language, which is masked by the term "climate change". If there is going to be any climate change due to anthropogenic greenhouse gases, it will be because they cause global warming.
So the most important thing that we want to know is how much of a global temperature rise would be caused by anthropogenic greenhouse gases, of which CO2 is the primary contributor. The agreed upon measure of climate sensitivity is the global average temperature change that would be caused by a doubling of the atmospheric CO2 concentration.
To answer that question, we need to know how much additional downwelling infrared radiation would be produced at the top of the atmosphere by the increase of CO2. For a doubling of the CO2 concentration, the UN IPCC modelers (and I agree) say that we should expect an additional 3.7 watt/m^2 due to CO2, which they call the "climate forcing". The question is, how much of a surface temperature change would this produce?
Historically, we have gotten a 33 C warming for a total forcing of all greenhouse gases of about 101 watt/m^2. That gives us a long term average, ice ages and all, of 0.33 C per watt/m^2. More recently, since pre-industrial times, we have gotten about 0.6C (out of 0.8C total counting solar contributions) for a forcing of about 1.8 watt/m^2. Again, this is about 0.33C / watt/m^2. Another way of looking at this is that we currently have about 239 watt/m^2 leaving the top of the atmosphere for 390 watt/m^2 radiated from an average 15C ( 288 K) surface. For 288 K, we get an additional 5.4 watt/m^2 for each 1 C rise of temperature. Thus if the outgoing infrared at the top of the atmosphere would be reduced by 1 watt/m^, then to maintain equilibrium with the incoming solar visible and ultraviolet radiation, the surface would have to radiate 390/239 watts/m^2. That would correspond to at temperature increase of (390/239)/5.4 = 0.3 C. So any way one looks at it, it seems that we should expect something like 0.3-0.33 C per watt/m^2.
With these preliminaries in mind, we can have a look at an analysis of some real world data here:
http://wattsupwiththat.com/2012/12/10/an-interim-look-at-intermediate-se...
The author, Willis Eschenbach, has taken five years of annual average surface temperature data and five years of CERES satellite measurements of downwelling infrared radiation and correlated them, using time-lagged correlations for 0,1,2 and 3 months. This was done cell by cell for a 1 degree X 1 degree grid of the whole earth. He did a linear regression on a gridcell-by-gridcell basis. Dataset size was limited by the length of the shortest dataset, which is the CERES dataset, about five years of monthly data. For each gridcell, he regressed five years of TOA (top of atmosphere) imbalance data against five years of surface temperature data for each of four time lags. Then using the best (highest R^2 - correlation coefficient) regression equation for each box, he calculated the temperature change for a decrease of 3.7 W/m^2 in TOA outgoing radiation.
These data showed three very interesting and somewhat unexpected results. First, there is no significant correlation at any time lag in the intertropical convergence zone near the equator. Second the global average climate sensitivity is less than 0.5C for 3.7 watt/m^2. Third, the sensitivity is actually negative for regions with ocean temperatures above about 28 C. This very strongly suggest that tropical thunderstorms control the surface temperatures in the tropical zones 18N-18S.
I strongly recommend that the article be read carefully by anyone who is curious about earth's climate sensitivity. It is based entirely upon real world data analyzed in a model independent way.
Stan
Tony,
I believe that if Mark used the same data and time scale that I used, his chart would be the same as mine.
Stan
Wow, lots of interesting thoughts....where to begin.
Extinctions of species are happening at alarming rates for a number of reasons from habitat destruction and invasive species to climate change. This isn't new news, Peter Raven, then President of AAAS (the largest scientific organization), stated:
as part of forward for the AAAS Atlas of Populations & Environment. We are literally wiping things out faster than we can name them in many places. If you want names though, here is a good place to start (link). I'm not sure how much faith to put in the back of the envelope calculations that half of all species are likely to be gone by 2100, but any way you slice it, it is a ridiculously high amount. This is a big part of the reasons why we are currently inhabiting a new geological period called the Anthropocene where we dominate biogeochemical cycles and most everything else.
Speciation happens in a variety of ways and at a variety of speeds. The dichotomy of either punctuated equilibrium (macro evolution) or gradualism (micro evolution) is another in a long line of simplistic but false choices. The ingredients for speciation are selection pressure (meaning a better chance of surviving if you are different), resource availability (something nothing else is already using or a chance to be better at it) and TIME. There are definitely periods of rapid speciation, unfortunately they generally occur shortly after large scale extinction events (Good bye dinosaurs, hello mammals) when there a lot of empty spots at the dinner table.
We are currently clearing the slate for what will come next. The last time the planet experienced a release of greenhouse gases (50+ million years ago) it was accompanied by another mass extinction event. Curously enough that was the worst extinction event for benthic foraminifera (little critters living sediments at the bottom of the oceans) but mammals came out quite well in the end. Note, we are talking a thousand odd years of extinction and thousands to millions of years of evolving species.
In the end all will be well, life will go on. Whether we will be part of it is still in question.
Mark
If I set my mind to it there will be an acceleration in speciation. Genetic engineering is tremendously jolly fun.
Especially if we can bio-engineer an organism that can convert water into hydrogen for use in our cars. When it escapes we lose the oceans. But look on the bright side, we get to keep our cars. Just like Thelma and Louise.
Stupid hairless ape. The first candidate for genetic modification will be you.
It seems inconceivable.
But recently I have been hearing that the rate of climate change has been greatly underestimated. I am now starting to believe that the added positive climate feedbacks are now accellerating the rate of global warming.
And the past few months I have been hearing that it would now be pointless to make any attempt to combat climate change. And in fact efforts to reduce greenhouse gasses at this point could acually make matters worse
If this author is telling it like it really is (and I suspect that he is), perhaps it really is the end of the World after all.
http://howtosavetheworld.ca/2012/12/20/preparing-for-collapse-non-attachment-not-detachment/
It seems inconceivable.
Well, the Mayans told us. In a few more hours you won't have to worry about 2050.
Stan.
Let's assume for a minute that it's 6C warmer by 2050. What would it mean in term of solar energy absorbed in 37 years? Is it even remotely physicaly possible giveen the thermal inertia of the planet? Ca you help out with the math?
Thanks!
SailAway,
Getting 6 C by 2050 seems farfetched unless we intentionally trigger to so-called clathrate gun. Even then, I am not sure that it is likely to happen that quickly simply due to the thermal intertia of the oceans and glaciers in Greenland and Antarctica. Roughly 90-95% of the incipient energy imbalance goes into warming or melting water. We've warmed by around 0.7C in the last 30 years or so. Getting an extra >5C in the next 40 years would require truly massive changes in greenhouse gases and Earth's albedo. This certainly wouldn't mean that all is well if we don't manage this incredible feat of climate suicide in 40 odd years. We may get there yet around 2100.
Such rapid warming would lead to greatly accelerated mass loss from the icesheets in Greenland, Western Antarctica and increases from East Antarctica. Melting those giant ice blocks would be a giant heat sink that would attenuate the rise in temperature but it would do so at the cost of flooding the worlds oceans very quickly. In other words, although we might not warm so fast the cost would be rapid sea level rise of several meters this century, flooding coastlines and yielding terrible storms. As things stand, most estimates are for 1-5 meters, which will make many, many cities untenable.
Some recent food for thought on that score came out in the last week in Nature Geoscience showing much of the western Antarctic icesheet is warming twice as fast as predicted (see BBC article here, and Bromwich et al 2012 abstract here))
The map is just correlation coeficients but the warming has been 2.4C between 1958 and 2010. While Greenland gets much of the press, the Western Antarctic ice sheet may be more unstable because most of it is currently grounded below the waterline. Basically the ice is frozen to the ground or still too heavy to lift but once the water level gets higher, then much of the sheet could rapidly float (just like an ice cube in your glass) and collapse with an ultimate 5 m sea level implication. The big brother in East Antarctica only has 30% below water line but that is another 20-25 m of sea level. Ultimately, if we somehow manage to stay on the 'business as usual' emissions path then over the next few centuries we will have changed coastlines world wide with 10s of meters of sea level rise (See Hansen new pdf).
Lest you think he is just a harbinger of doom touting positive feedbacks, Hansen and Sato (2012) see exponential increases in the rate of ice melting/sea level rise with a 5-10 year doubling time, they ultimately believe that once we reach about 1 m of sea level increase that strong negative feedbacs from all of the melting icebergs will dampen the temperature rise and hence slow the exponential rate of increased melting. I can't grab the figure from the pdf, but if you go to the Hansen and Sato pdf linked above and scroll down to Figure 9 you will see the future simulations with (left) and without (right) ice melt. As you can see the melting would lead to a much cooler North Atlantic and a moderate cooler Southern Ocean with an overall global amelioration of land temperature increases. If you think the ice will somehow hold off from melting, plan for a heck of a lot warmer near future.
Overall, if we manage to keep finding more and more fossil fuels to burn or accidentally release (melting permafrost etc) then we will have an atmosphere akin to what existed 32 million years ago before Antarctica froze up. It would take a while, hundreds to thousands of years, but we'd be putting an end to ice ages for the foreseeable future.
Mark
Thank-you Mark for taking the time to write this post. This is truly fascinating.
Here is a snapshot of the picture from the pdf document that you mentioned in your post:
Best Wishes and Happy New Year to all!
Fred
...
These data showed three very interesting and somewhat unexpected results. First, there is no significant correlation at any time lag in the intertropical convergence zone near the equator. Second the global average climate sensitivity is less than 0.5C for 3.7 watt/m^2. Third, the sensitivity is actually negative for regions with ocean temperatures above about 28 C. This very strongly suggest that tropical thunderstorms control the surface temperatures in the tropical zones 18N-18S.
Everyone agrees that the no-feedback warming is around 0.25°C/W/m² just from basic physics. The best evidence for feedbacks comes from palaeoclimate data. Hansen in numerous papers finds that fast feedback climate sensitivity for states between last glacial maximum and pre-industrial Holocene is 0.75 ± 0.125°C/W/m² (e.g. Hansen & Sato, 2011). This is derived from the relationship between slow feedbacks (ice sheets, vegetation, greenhouse gases) and temperature rise - basically, the orbital forcing is negligible, the slow feedbacks are a forcing of ~6.5W/m², temperature rise is ~5°C, hence fast feedback climate sensitivity (the net of cloud feedbacks, sea ice, water vapour and aerosols) is ~0.75°C/W/m². Surely this is a far more reliable figure than Eschenbach's 5 years of data? Also it gives us the slow feedback figure which must be around double the fast feedback climate sensitivity.*
EDIT: * I should say that this is the slow feedback for planetary albedo alone - the greenhouse gas feedback is expected to make this larger still, if we don't halt global warming before carbon cycle feedbacks really kick in.
Everyone agrees that the no-feedback warming is around 0.25°C/W/m² just from basic physics. The best evidence for feedbacks comes from palaeoclimate data. Hansen in numerous papers finds that fast feedback climate sensitivity for states between last glacial maximum and pre-industrial Holocene is 0.75 ± 0.125°C/W/m² (e.g. Hansen & Sato, 2011). This is derived from the relationship between slow feedbacks (ice sheets, vegetation, greenhouse gases) and temperature rise - basically, the orbital forcing is negligible, the slow feedbacks are a forcing of ~6.5W/m², temperature rise is ~5°C, hence fast feedback climate sensitivity (the net of cloud feedbacks, sea ice, water vapour and aerosols) is ~0.75°C/W/m². Surely this is a far more reliable figure than Eschenbach's 5 years of data? Also it gives us the slow feedback figure which must be around double the fast feedback climate sensitivity.*
Welcome to the discussion of climate change on PP, Icarus62. Tbis is one of the few internet forums where discordant views of the subject are discussed peacably. Thank you for reiterating my point about the no-feedback sensitivity. Perhaps having someone else state that it is just basic physics will help to convince the many that disagree. The only way that the climate models get large temperature increases for a CO2 doubling is by including large feedback factors. It is definitely a start in the right direction to try to examine historical climate records to see if these are justified, however, the Hansen study that you cited is so seriously flawed that it I give it no credibility. It is based on two assumptions that are simply wrong. First, it assumed the sun had no influence during the last deglaciation period. Second, it assumed that CO2 was the driver of the change and found that it would have to be aided by positive feedbacks of a factor of 3.
In view of the well established role of solar flux in the Milankovitch glaciation cycles, (shown in the second graph below for the last 400,000 years) I think that it is simply wrong to exclude solar influence. Consider the following comparison of solar flux at the start of deglaciation to present values. This plot is for solar insolation at 65 N latitude, with similar results for a southern latitude.
Note that the rapid deglaciation around 12000 years ago corresponded to very strong solar forcing in the summers. It is simply unjustifiable to neglect this influence.
Considering that temperature rises preceded the increases of CO2, it is pretty clear that increasing CO2 is an effect of warming rather than a cause. It should also be clear that the source of the CO2 is the oceans. The solubility of both CO2 and methane decreases with increasing ocean temperatures, accompanied by release of these gases to the atmosphere. These increasing greenhouse gas concentrations are among the more important positive feedbacks for the solar driver of the deglaciation. Note that there is no reason that any other terrestrial sources of these gases, such as volcanoes, should be correlated with Milankovitch cycles.
What Hansen and Sato did was to superimpose the temperature and CO2 charts on a scale that obscured precedence and then found that they could be apparently superimposed by multiplying the calculated forcing from the latter by a sensitivity feedback factor of 3. The methods that they used to determine forcings and to scale ice core temperatures into an equivalent "global temperature anomaly" are also questionable.
Finally, there is an important question that was not addressed at all. With such large positive feedbacks, why did the temperature ever stabilize? The obvious answer is that the positive feedbacks to whatever was driving the temperature increase had ceased to operate. Thus there is no reason to expect them to operate in the present deglaciated times. As I have noted in previous posts, they have not been operating in the warming from pre-industrial times to the present. I am all for the use of verifiable empirical data rather than relying on models, but the Hansen & Sato study doesn't pass muster.
Stan
Hi SailAway
Well, one way to get to 6C by 2050 would be to have the present global temperature anomaly of about 0.3C increase exponentially at a rate of about 8% per year. This is how it would look:
UGLY! when plotted on this time scale, isn't it? What's worse, it looks like we would hardly notice for 10 years. But don't let the graph fool you. There would actually be a temperature increase of 0.37 C in the next decade. That is more than twice as fast as temperatures rose in the most recent rapid warming period from about 1976-1997. That would definitely be noticed and alarm bells would be ringing loudly. But if that were to occur it is almost impossible to imagine that there would be any way of stopping some additional profound warming.
As for what might cause the temperature to rise that fast? That is a relatively simple, but interesting problem in heat transfer. The oceans are huge thermal buffers for the earth. The first 25 meters of the oceans has about ten times the heat capacity of the atmosphere. So if you want to increase surface temperatures it is absolutely necessary to heat the upper regions of the oceans. But to get the temperature to rise exponentially, it is also necessary that the heat be ramped up exponentially. Surprisingly, that can be done with a modest beginning of only about an extra 0.8 watt/m^2 meter impinging on the oceans surfaces. That is small potatoes compared to the 170 watt/m^2 presently impinging on them on average. From that modest beginning, you would have to increase the surface heating rate to more than 50 watt/m^2 by 2050, just to compensate for surface radiation losses. Additional heating would also be required to offset conduction losses to deeper parts of the ocean. For the amount of ocean that produces its present thermal lag of about a decade from surface condition changes, it would require an additional factor of about 2 on the heating rate at 2050. So my rough guess is that 0.8 watt/m^2 now, increasing exponentially to about 100 watt/m^2 by 2050 would about do it. Buy stock in air conditioner companies and bathing suit makers.
Stan
Can't lay my finger on it right now but there was some recent research that modifies earlier understandings about the CO2 release delay, in the past, and shows that the delay, if any, was small. However, it has always been understood that the release of CO2, by whatever means, worsens the warming. Today's situation is different from the past because humans are releasing that CO2 (and other greenhouse gases) through their actions thus initiating a warming and feedbacks which release more carbon are likely to exacerbate the warming.
The effects of solar irradiance variation has been looked at closely for the current warming and does not explain it. What does explain it is the release of greenhouse gases due to human behaviour.
The current issue is about what is happening this time. Though research into past climate can help us understand the workings, the human factor is unique in our case and needs to be a focus.
Tony
First,
Welcome aboard Icarus62 and thank you for providing information rich content! As Stan mentioned, this is a forum for discussion in the hopes that if we can openly debate climate change-related matters and provide clear and coherent explanations of our current understanding of what is a broad ranging and often complex subject.
Stan,
I do not think that you are fairly categorizing Hansen and Sato (2012). I assume that you are referencing the book chapter and not the link I had provided to the current pdf that is openly available "Update of Greenland Ice Sheet Mass Loss: Exponential?". Do you have access to the book? I do not so I cannot speak to all of your points. I seriously doubt that one of the most accomplished and respectable climate scientists ever claimed that the sun had no influence on climate changes for the last deglaciation, particularly in a book paying tribute to Milankovitch.
I know of no one who argues with solar energy changes during Milankovitch cycles (Earth's changing orbital relations to the sun for those new to the thread) as being the key initiator of glaciation/deglaciation cycles. Similarly though, no one can make a credible claim that these gradual and relatively small changes in solar irradiance could yield the massive climate transformation of the planet by themselves.
Please look back at (#633 Time to get something straight about climate feedbacks). As previously stated by myself and in the scientific literature for 20+ years, the solar changes preceed the increases in CO2 by on the order of 1000 years. You correctly note that the source of the outgassing CO2 is the oceans as water temperature increases reduce the gas solubility. The released CO2 mixes in the atmosphere across the planet and starts acting to globally amplify the slowly increasing solar signal. Where you have gone astray is incorrectly inferring that the major global temperature increase occurs before the CO2 increases. More than 90% of glacial-interglacial warming happens 'after' the CO2 increases.
The sequence, therefore, is initiated by changing orbital cycles. In the case of deglaciation, small increases in solar energy begin to heat the oceans, particularly near the equator. The warmer waters slowly outgass, increasing quantities of CO2 that acts in its greenhouse gas capacity to trap more solar energy for longer periods, thereby accelerating warming of the planet. This amplification is increased over time as both water vapor and CH4 increase in concentration within the atmosphere as well. As ice sheets collapse, the changed planetary albedo reinforces the positive feedback in the warming process. The process continues until a new stable (relatively) climate state is reached. What we are currently doing is analogous to cranking up the volume on the solar gain.
Hansen and Saito's point in the online pdf is that the ice melt in Greenland and Antarctica is an exponentially increasing process that yields very different implications than the frequently used linear extrapolations. From the sample pages that I can access in the book chapter it is clear that they are using paleodata to indicate that we are within 1C of the warmest interglacial period ever and that to blithely shoot past that level is the height of folly and fraught with unimaginable risk.
Happy New Year to all,
Mark
Thanks Stan. Hansen certainly acknowledges the cause of the glaciation/deglaciation cycles of the past few million years - the large change in high northern latitude summer insolation is the main driver, reducing or increasing the extent of ice sheets and thereby altering planetary albedo. Greenhouse gas changes are a feedback to that forcing, amplifying it by about a factor of two. Globally averaged orbital forcing is a small fraction of a Watt. I don't see Hansen arguing anywhere that greenhouse gas change is a forcing in these cycles; quite the contrary. Just as one example, from 'Climate Sensitivity Estimated From Earth's Climate History':
Hansen acknowledges that his conclusions hinge more on an accurate determination of global temperature change between glacial minima and maxima than on anything else :
You ask: "With such large positive feedbacks, why did the temperature ever stabilize?" - surely because the forcing (not the feedbacks) ceased to operate - as shown in your graph of 65°N insolation.
EDIT: If I remember correctly, Hansen again acknowledges the change in high latitude summer insolation as the main driver of Milankovitch cycles when he points out that the gradual decline in Holocene global temperature is consistent with the ~8,000 year decline in that orbital forcing, and crucially that on this basis we would expect global cooling to be continuing for thousands of years into the future, whereas we see rapid global warming instead. Other papers say the same thing, e.g:
Recent Warming Reverses Long-Term Arctic Cooling Darrell S. Kaufman1,*, David P. Schneider2, Nicholas P. McKay3, Caspar M. Ammann2, Raymond S. Bradley4, Keith R. Briffa5, Gifford H. Miller6, Bette L. Otto-Bliesner2, Jonathan T. Overpeck3, Bo M. Vinther7, Science 4 September 2009: Vol. 325 no. 5945 pp. 1236-1239 DOI: 10.1126/science.1173983 http://www.sciencemag.org/content/325/5945/1236.short
http://guymcpherson.com/2013/01/climate-change-summary-and-update/
The climate situation is much worse than I’ve led you to believe, and is accelerating far more rapidly than accounted for by models. Ice sheet loss continues to increase at both poles, and warming of the West Antarctic Ice Sheet is twice the earlier scientific estimate. Arctic ice at all-time low, half that of 1980, and the Arctic lost enough sea ice to cover Canada and Alaska in 2012 alone. In short, summer ice in the Arctic is nearly gone. Furthermore, the Arctic could well be free of ice by summer 2015, an event that last occurred some three million years ago, before the genus Homo walked the planet. In a turn surprising only to mainstream climate scientists, Greenland ice is melting rapidly.
Ocean acidification associated with increased atmospheric carbon dioxide is proceeding at an unprecedented rate and could trigger mass extinction by itself. Already, half the Great Barrier Reef has died during the last three decades. And ocean acidification is hardly the only threat on the climate-change front. As one little-discussed example, atmospheric oxygen levels are dropping to levels considered dangerous for humans.
An increasing number of scientists agree that warming of 4 to 6 C causes a dead planet. And, they go on to say, we’ll be there by 2060. The ultra-conservative International Energy Agency, on the other hand, concludes that, “coal will nearly overtake oil as the dominant energy source by 2017 … without a major shift away from coal, average global temperatures could rise by 6 degrees Celsius by 2050, leading to devastating climate change.” At the 11:20 mark of this video, climate scientist Paul Beckwith indicates Earth could warm by 6 C within a decade.
Hello Doug --- and everyone else,
Sorry to be so scarce of late but I am going to be largely out of circulation for at least another few weeks.
Just saw this post and thought I better reply quickly. Things are bad but not as catastrophic as this. McPherson generally presents the worst case but what I have seen has generally at least been a credible representation of it. This bit on dropping oxygen levels being dangerous for humans is pure nonsense though.
Here is the link to the actual research (link). Yes, oxygen levels are dropping as a function of fossil fuel combustion but the effect is tiny. Here are the graphs that the hype is derived from.
What the fearmongers are not cognizant of is units of measure. Rising CO2 levels are measured in parts per million (ppm), oxygen levels in the atmosphere are measured in percent (%), which could also be termed parts per hundred. In our case it is 21%. Currently CO2 is about 394 ppm. In the same units oxygen (O2) is 210,000 ppm. CO2 is a trace gas (meaning small fraction).
While the researchers do say:
They follow that up with:
Also following up some of the other misrepresented materials. Yes there was a time in the 'prehistoric' past when oxygen levels reached potentially as high as 35%, that was a geologically brief period and the subsequent drop to 21% had nothing to do with our activities. Note, at 35% O2, fires are almost unstoppable. Even 'Nomex', the fire-resistant materials used by firefighters would burn. The wettest swamps could burn as well. Not too surprisingly, there is a lot of charcoal deposition at that period of high O2.
Climatically things are serious but everyone can at least breath easier about the oxygen levels. Where oxygen levels are a problem is in the oceans where increased temperature and stratification of the water layers, combined with fertilizer runoff, is creating dead zones of very low dissolved O2.
Mark
All,
For those interested in either seeing or participating in the latest 4 year U.S. NCADAC Report, see below. It is basically a U.S.-centric mini version of the IPCC climate assessments. The full draft report or sections of interest can be found here (scroll to the bottom of the page). This is a work in progress, so if you want to see it before it is 'official', or even have your comments about aspects of it addressed, here is your chance. Note, I am in no way associated with this report and have not yet had time to read it though I imagine that it is a similar to, though more current than, the 2009 report.
Mark
Thanks for the heads up regarding oxygen, Mark. I do have a criticism of Guy McPherson regarding his use of the research or opinions of other scientists (and some non-scientists), in that he will often cite them as though they were facts. However, in his defence, he doesn't say, explicitly, that they are facts, or even credible but, certainly, using them in his talks and writings, in this way, gives the impression that they are credible. He may even continue to use some "fact" after it has been pointed out that it's no longer valid.
Anyway, overall, Guy is on the right track and most of what he writes/says is spot on, I think.
Regardless of one's point of view about global warming, it is useful to understand opposing viewpoints. A good summary of the reasons for expecting less than catastrophic warming in the short term is presented here.