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Christopher Johnson

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Christopher Johnson  asked the Naked Scientists:
   
I am a huge fan of your show, and I have a question about climate change and global warming.  
 
I consider myself an environmentalist.  I am concerned about the amount of pollution we generate, the animals we push to extinction, and the resources we exhaust.  However, I don't believe that we are the driving force behind global warming.  It concerns me that whenever we hear about the effects of global warming, it is always mixed with the message that we are irrevocably destroying the earth.
 
It can hardly be disputed that the earth is warming and the percent of greenhouse gasses in the atmosphere is increasing.  I would like to know, what evidence is there that humans are contributing to this significantly?
The earth's temperature rises and falls cyclically, and it has been on the increase since before the industrial revolution.  We currently are not near the highest temperature that we know the earth to have reached.  The polar ice caps have melted several times before.  So, what percentage of the current warming trend are due to humanity and what percentage is natural?
 
Thanks,
Chris Johnson
West Virginia
United States

What do you think?


 

Offline frethack

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What proportion of global warming is attributable to humans?
« Reply #1 on: 21/07/2009 19:11:08 »
It would be, at this point, impossible to state with any accuracy what the human induced portion of climate change is.  The only accurate statement that can be provided is "less than we thought it was 10 years ago." 

As far as humans contributing significantly to the level of greenhouse gasses in the atmosphere, this I would say is undoubtedly true.  Soil and oceanic outgassing are contributors, but from all evidence that I have read, humans are responsible for the lionshare.  Not just through carbon emissions, but also through mass deforestation.  This does not necessarily mean that GHG's are the only contributor to climate change, though.

My area of research is in connections between solar variability and decadal/centennial scale migrations of the Intertropical Convergence Zone (ITCZ).  The research conducted in this topic is fairly recent and has not yet been widely considered in General Circulation Models, nor by the IPCC.  By way of explanation, Ill post my term paper from last semester...keep in mind that it is written for a climatology class and may not be wholly self explanatory (The figures would not transfer, so I included them at a the bottom, but without captions):

Solar Forcing and Atlantic Climate during the Holocene
     The sun is by far the dominant supplier of energy to the Earth’s climate system, and being a variable star, its energy does not remain constant.  As far back as the 17th century, sunspot activity was thought to foretell the intensity of summer and winter temperatures, the length of the growing season, and the onset of disease.  Though these claims would today be viewed as tenuous at best, the modern era has seen researchers beginning a more rigorous test of solar influence on climate.  Trends can be detected between solar flux and paleoclimate records, possibly affecting even the rise and fall of ancient civilizations (Zhang et al. 2008), but the physical mechanisms influenced by the sun, that are internal to the climate system, remain almost wholly undiscovered.  A proposed mechanism of solar influence, the effect of the Intertropical Convergence Zone (ITCZ) on Gulf Stream transport variability, will be discussed in this text.
     To interpret long term climate trends and solar influence, it is necessary to look at Northern Hemisphere (NH) temperature proxies and to very briefly discuss their methods, strengths, and weaknesses.  There is some debate within the climate community on the temperature variability between the Medieval Warm Period (MWP) and the Little Ice Age (LIA), and how those two periods compare with the current warming trend.  Two NH temperature reconstructions will be discussed, Esper et al. 2002 and Moberg et al. 2005, and were chosen because of their use in Poore et al. 2003/2004, Richey et al. 2007, and Lund et al. 2006.
     Though generally considered as temporally accurate proxies for temperature reconstructions and radiocarbon production, researchers have had difficulty preserving low frequency climate signals in tree-ring chronologies.  As a tree ages, it tends to create narrower growth rings that can obfuscate the climate signal contained within them, so sets of mathematical growth functions are applied to each individual ring-width chronology to detrend the signal over the tree’s life span. This has a tendency to remove not just the growth regressions as a tree ages, but because an individual tree’s life may span 200 to 400 years or more, it also compresses and effectively loses the long term climate signal over the life span of individual trees (Esper et al. 2002).
     In an attempt to preserve low frequency trends in tree ring based temperature reconstructions, Esper et al. 2002 used a Regional Curve Standardization (RCS) method.  After dividing tree ring chronologies into groups that exhibit linear and non-linear growth trends, an average growth function was fitted to detrend the groups of data as a whole rather than being fitted to individual ring-width records.  The two independent chronologies, showing similar peaks and troughs, were then stacked to form one tree ring record.  Low frequency trends were preserved, and a MWP and LIA were clearly evident from the data (see figure 1).  Esper acknowledges that a lack of robust data sets from 800 to 1200 ybp may still contribute to a regional bias in the data, and that further individual ring-width sets need to be developed to strengthen our understanding of this era.
     A separate multiproxy technique, wavelet transform (WT), was employed by Moberg et al. 2005 that included high resolution tree ring chronologies, as well as lower resolution sediment cores, ice cores, and borehole measurements.  These data are calibrated, weighed, and stacked to produce an age independent NH temperature record that preserves centennial and millennial scale variability.  Critics of this technique assert that WT overestimates the height and depth of low frequency temperature variability, and though Moberg has put forth some evidence to the contrary, no consensus has been reached on the effectiveness of this method.
     Though the amplitude of paleo-temperature change is still under debate, many individual regional proxy reconstructions, much like the two widely cited NH temperature reconstructions previously discussed, show general agreement in a thermally elevated MWP, a cooler LIA, and a current modern warming period.  Some researchers have cited variances in heat transport to northern latitudes via the Gulf Stream as one component that may be affecting Atlantic regional paleotemperatures.  Lund et al. 2006 provides a detailed estimate of Gulf Stream flow over the past 1.2 ka.
     Approximately 31 Sverdrup’s (Sv) [1 Sv = 1 x 106 ms-1] of water are transported from the Gulf of Mexico (GOM), through the Florida Straits, and into the North Atlantic (NA) via the Gulf Stream.  This contributes a large portion of the warmth received in the northern latitudes in the Atlantic Basin.  Using  delta-18O of foraminiferal assemblages from a sequence of transecting, high resolution sediment cores, the density structure and discharge volume through the Florida Straits was able to be ascertained, at depth, for the past 1.2 ka.
Lund’s findings showed an overall transport reduction of ten percent throughout the LIA, with the largest percent reduction in benthic waters associated with the Antarctic Intermediate Water (AIW) (see figure 2).  The AIW is the return flow for the North Atlantic Deep Water (NADW) and can be used to infer the strength of the Meridional Overturning Circulation (MOC).  Given that the Gulf Stream presently supplies about 1.3 x 1015 W of heat to the NA (Lund et al. 2006), a ten percent reduction is a considerable amount of energy lost by the northern latitudes, and could explain at least some of the cooling during the LIA.
     It has long been known that seasonal insolation differences drag the ITCZ toward the northern or southern hemisphere during their respective summers on intra-annual time scales, but until recently, little serious effort has been made to qualitatively and quantitatively measure the effects of long term solar variability on the average position of the ITCZ.  Sediment cores from the GOM, the Cariaco Basin, and Lake Miragoane all show some agreement that the average position of the ITCZ has migrated on decadal and centennial scales.  This phenomenon is also seen in speleothem records from China (Zhang et al. 2008; Yancheva et al. 2007).  Though orbital parameters are thought to be the principal forcing agent on the consistent southward migration of the ITCZ throughout the Holocene (Haug et al. 2001), the mechanism controlling the centennial scale fluctuations remains in question.
     As the Yucatan Current enters the Caribbean and flows into the Gulf of Mexico (GOM), it bifurcates into two currents, the Florida Current and the Loop Current.  While the Florida Current continues along the arch of Cuba and through the Florida Straits, the Loop Current pushes with varying degree into the GOM before rejoining the Florida Current to form the Gulf Stream.  This varying incursion of the Loop Current on centennial time scales is related to the latitudinal position of the ITCZ, with a higher average ITCZ position corresponding with deeper Loop Current penetration (Poore et al. 2004). 
     A box core taken from the northern GOM in the Pygmy Basin region (MD02 2553) provides a high resolution record that exhibits sensitivity to Loop Current position, and by extension ITCZ position, over the past 5000 years.  The planktonic foraminifer Globigerinoides sacculifer can be found in many tropical regions around the world, but in the Atlantic portion of the Western Hemisphere Warm Pool, the foram rides the currents out from the Caribbean Sea, making their relative abundances in the northern GOM dependent upon Loop Current vigor (Poore et al. 2003/2004).  As total solar irradiance increases, the ITCZ and the westerly trade winds are drawn to slightly higher northern latitudes.  Because land generally accepts and radiates heat more readily than the oceans, this northward migrating effect of the ITCZ shows an exaggerated refraction over continental masses.  This effect can be demonstrated by the NH summer and NH winter positions of the ITCZ in figure 3.  As the NH rotates toward the sun during summer, the trade winds are effectively pulled across Central America, strengthening the Caribbean surface currents and pushing the Loop Current into the northern GOM.  This effect allows G. sacculifer to enter the Pygmy Basin region and therefore become a proxy for general ITCZ position, trade wind strength, and Loop Current vigor.
     Loop current strength in the GOM exhibits some correlation with proxies of NA climate, containing troughs that match well with ice rafted debris (IRD) events reported in Bond et al. 2001 (see figure 4).  Most of the IRD events over the last 5 ka can be traced to large drops in northern GOM abundances of G. sacculifer, with paired events at about .4 and .6 ka, 1.1 and 1.5 ka, 2.9 and 3.2 ka, and 4.1 and 4.6 ka over the past 5000 years (Poore et al. 2004).  In Bond et al. 2001, many NH cooling events are correlated to decades of heightened 14C production, indicating extended minima in solar activity, commonly called grand minima.  If the findings of Lund et al. are taken into account, lower abundances of G. sacculifer might signify less overall Gulf Stream transport, which could translate into lower NA temperatures (Richey et al. 2007) resulting in IRD events.
Plotting G. sacculifer abundances directly against proxies of solar activity, such as 14C production, shows strong correlations over the past 1.3 ka.  The MWP, lasting from about 1.2 ka to .8 ka, is noted to have extended periods of high solar activity with a single major punctuation event, a grand solar minimum called the Oort minimum, at about 1.1 ka.  Abundances of G. sacculifer follow in good agreement throughout the MWP, dropping off during the Oort minimum and returning to previous levels when solar activity increases.  The LIA is generally accepted to have begun around the onset of the Wolf minimum at around .8 ka, with two successive grand minima sending solar activity into depths that are not matched in Holocene solar records.  The Spörer minimum is by far the longest of the recent grand minima, beginning between .7 and .6 ka, and lasting close to one hundred-fifty years.  During this time period, Loop Current vigor exhibits a deep low, once again beginning recovery as the Spörer minimum comes to a close.
     The first of the grand minima to be visually observed and recorded is the Maunder minimum, beginning at about .4 ka.  This third successive minimum did not last as long as the Spörer minimum, the Maunders duration being about seventy years, but it is associated with the coldest period of the LIA.  Relative abundances of G. sacculifer reached their lowest levels during the Maunder minimum and again began a recovery as the grand minimum ended.  Throughout the LIA, Loop Current strength showed a general decline, agreeing with the aforementioned study by Lund, but the strengthening of Gulf Stream transport during the current warm period seen in Lund et al. 2006 cannot be corroborated because the Loop Current record in Poore et al. 2004 ends at around .2 ka.
Thus far, IRD events have been the only evidentiary link offered to connect wind and surface currents in the GOM with northern latitude climate in the Atlantic basin, but there are other NA proxies that are in agreement with these studies from the subtropics.  Research reported by Richey et al. 2007 asserts that though fluxes in sea surface temperatures (SST) in the northern latitudes are decoupled from SST in the subtropical GOM, sea-salt-sodium (ssNa) from the GISP2 ice core still show a well correlated shift from more negative values to more positive values at about .6 ka, corresponding with a similar change in abundances of G. sacculifer and delta- 18Ocalcite from a second box core from the Pygmy Basin, GOM (PBBC-1).  Changing atmospheric circulation and intensified winter winds from the Icelandic Low (IL), a dominant low pressure region in the North Atlantic, pick up sodium from sea spray and carry it inward toward Greenland, increasing the levels of ssNa in glacial ice deposits.  As a climate proxy, ssNa is used to represent the intensity of the IL, which at higher values indicates heightened NA storminess.  If this link can withstand continued rigorous testing, it would mean that fluctuating Gulf Stream transport into the NA, induced by solar activity, would be a major contributor to the variable climate of the northern latitudes. 
     Though a link between solar activity and climate has been debated for many years, modern technology has only recently allowed us to begin exploring these correlations in earnest.  Radioisotope proxies have extended the limited knowledge of solar flux from the visual sunspot record of about three hundred years, to a more substantial time, spanning into the Wisconsin glaciation.  Still, the cause of our sun’s variability remains elusive.  It is understood that sunspot cycles such as the ~22-year Hale cycle, composed of two ~11-year Schwabe cycles, are solar magnetic reversals, but the mechanism governing the variable length and intensity of these cycles is not known.  Even less is known about the rhythms of the longer solar cycles, the ~87-year Gleissberg and ~210-year deVries/Suess cycles. At least one study has attributed the 1470 ± 500 year periodicity reported by Bond et al. 2001 to harmonics in the overlapping Gleissberg and deVries/Suess cycles (Braun et al. 2005), but this periodicity is only very weakly correlated to the paleoclimate record, if at all.
     There is a growing body of evidence from the GOM, as well as evidence from the Asian continent not discussed in depth here, that variability in solar insolation may have a pronounced effect on the average position of the ITCZ over decadal and centennial time scales.  As with any area of paleoclimatology, questions seem to multiply exponentially.  Aside from increasing the robustness of the present data, scientists might also ask why the ITCZ does not remain in a fixed, seasonal position.  Seasonal migrations come from a change in the focus of the sun’s maximum radiation from the northern hemisphere to the southern hemisphere as the earth revolves yearly.  Aside from minute changes in precession and obliquity, orbital forcings have largely remained the same since the MWP.  Why would the sun, giving its maximum insolation to approximately the same latitude year in and year out, draw the ITCZ variably north in the GOM?  Do centrifugal forces or Coriolis forces attempt to shift the ITCZ back toward the equator or is there some other mechanism at work?
     Though grand maxima and grand minima have a tendency to group together in solar reconstructions, researchers will continue to ask if there is any other underlying periodicities.  Even if a loose periodicity is found, how do such small changes in total solar irradiance, on the order of less than 0.2 Wm-2, have sweeping effects on the climate system as a whole?  It seems that additional feedback loops are necessary to explain the variability in the data.
     Much of the world depends directly on the predictability of the monsoons, and by extension the ITCZ, for their very livelihood.  Paleoclimate records show that what was once lush and productive land can turn to desert in the span of a century, or even just a few decades.  The sun and the ITCZ are each separately important factors in our climate, our agriculture, our water supply, and our culture.  Evidence correlating the two creates an importance in understanding how an ephemeral monsoon linked with a stochastic sun will affect natural resources, and possibly even the rise and fall of civilizations, into the future.

Figire 1


Figure 2


Figure 3


Figure 4


Figure 5


Figure 6

« Last Edit: 22/07/2009 14:03:48 by frethack »
 

Offline cjohnson

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What proportion of global warming is attributable to humans?
« Reply #2 on: 24/07/2009 16:26:25 »
Thanks for your response frethack.  This is what I had in mind.  Everyone hears about global warming, but rarely do we hear evidence.  Everything I have seen online would lead me to believe our contribution is small.  I am very interested in hearing the other side of the argument.  Anyone seen any estimates on:
1.  The contribution of the Greenhouse Effect to current climate change
2.  The contribution of carbon emissions and deforestation to the greenhouse effect as compared to soil and oceanic outgassing.

Thanks again,
Chris
 

Offline Karsten

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What proportion of global warming is attributable to humans?
« Reply #3 on: 25/07/2009 15:50:36 »
One thing seems to be clear: We are running out of the stuff that may contribute to/cause global climate change. I am afraid the effects of not having fossil fuels any longer will be much more dramatic than global climate change.
 

Offline frethack

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What proportion of global warming is attributable to humans?
« Reply #4 on: 25/07/2009 23:08:12 »
One thing seems to be clear: We are running out of the stuff that may contribute to/cause global climate change. I am afraid the effects of not having fossil fuels any longer will be much more dramatic than global climate change.

I whole heartedly agree with you...renewable resources are key to sustaining our energy needs.  Even if it is proven beyond a shadow of a doubt that the current climate change is mostly from natural effects, there is still urgent need to move to energy sources that do not feed social, political, and economic tensions (I know that statement is pretty broad, but, being in a science forum, Ill stop there).

Everyone hears about global warming, but rarely do we hear evidence.  Everything I have seen online would lead me to believe our contribution is small.  I am very interested in hearing the other side of the argument.  Anyone seen any estimates on:
1.  The contribution of the Greenhouse Effect to current climate change
2.  The contribution of carbon emissions and deforestation to the greenhouse effect as compared to soil and oceanic outgassing.

There is plenty of evidence that the earth has been warming for over two centuries, but I am assuming by "...but rarely do we hear evidence" that you mean evidence that GHG's are the cause of the warming.

Be careful what you read online.  There are ideologues on both sides of the debate that feed a lot of misinformation. 

As to the contribution of the Greenhouse Effect to current climate change, no one will be able to say for certain because we still do not know all of the natural processes affecting the climate.  There is still a LOT of research to be done in this area (future job security for me!).  Ill root around and see if I cant find any peer reviewed papers over natural vs. manmade carbon emissions. 
 

Offline Karsten

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What proportion of global warming is attributable to humans?
« Reply #5 on: 26/07/2009 19:47:27 »
Having written that the effects of running out of fossil fuels will have a huge impact on our society (it will probably bring the collapse of modern North American living), I prefer to err on the save side in regard to the effects of burning fossil fuels. We know it is bad (just turn on you car inside you garage with you in it and see how long you live), it is just a matter of scale. If it is disadvantageous to do it, why do it? Why do it if getting it wrong can cause so much mayhem?

My friends in Europe and Canada have a difficult time believing how many people in the USA still cling to the perception that humans have very little to do with the problem. They find it laughable.

One thing seems to be clear: We are running out of the stuff that may contribute to/cause global climate change. I am afraid the effects of not having fossil fuels any longer will be much more dramatic than global climate change.

I whole heartedly agree with you...renewable resources are key to sustaining our energy needs. 


Sorry to disagree. There is no way that renewable resources without the help of fossil fuels will allow us to continue living as we are now in the USA/Europe/Australia. Nuclear power maybe if we construct a bunch more nuclear power plants and learn to live with the waste and accidents. If you just take a look at the food production, the current human population basically "eats" oil. Once it is gone, the people will suffer and millions will starve. Fossil fuels drive our agriculture and construction and mining industry. Wind, solar, and hydro power don't work without fossil fuels.
 

Offline frethack

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« Reply #6 on: 27/07/2009 00:37:17 »
Quote
My friends in Europe and Canada have a difficult time believing how many people in the USA still cling to the perception that humans have very little to do with the problem. They find it laughable.
,

Laughable as they may believe it to be, there is plenty of evidence that both current and past climate change have a large natural component, and I do not know a scientist who can state with certainty the portion allotted to natural and anthropogenic factors.  Climate science is comparatively a very young field and we have a fairly rudimentary understanding of how climate works in the long term.  Erring on the side of caution is admirable, and I very much respect your position, but there is another side to the coin.  What if we spend this money on cap and trade and carbon cuts for very little effect on regional or global temperatures? (a good number of nations that have signed the Kyoto protocol have missed their promised marks)  The money spent would go a long way to building African infrastructure and improving their quality of life, as well as preparing for, if a large natural component exists, the inevitable effects of natural climate change in areas sensitive to sea level rise such as Bangladesh. (Historically, there have been many beneficial effects to currently underdeveloped regions during past climate optimums as well, but the effect of sea level rise in Bangladesh would be particularly catastrophic) 

Quote
Sorry to disagree. There is no way that renewable resources without the help of fossil fuels will allow us to continue living as we are now in the USA/Europe/Australia. Nuclear power maybe if we construct a bunch more nuclear power plants and learn to live with the waste and accidents.

Im not sure why we have disagreement on this point.  The switch to a majority renewable energy economy will likely take many decades to achieve, if not till the end of the century.  I do not expect a magical change from fossil fuels to renewable fuels.

Please understand that I mean no disrespect to you in my opinions.
« Last Edit: 27/07/2009 00:41:39 by frethack »
 

Offline Karsten

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What proportion of global warming is attributable to humans?
« Reply #7 on: 31/07/2009 15:27:34 »
Don't worry, I don't feel disrespected. And I hope you don't either.

My disagreement relates to the term "renewable resources are key to sustaining our energy needs". We cannot SUSTAIN our energy needs or life style without fossil fuels. The transition may be smooth if we begin now but as much as I would LOVE to see people beginning to live in ways that are sustainable, I fear that the transition will be rather rough, maybe even terrible. People have gotten used to waiting for miraculous technology solutions. People are not changing fast and I can understand why.

Erring on the side of caution is admirable, and I very much respect your position, but there is another side to the coin.  What if we spend this money on cap and trade and carbon cuts for very little effect on regional or global temperatures? (a good number of nations that have signed the Kyoto protocol have missed their promised marks)  The money spent would go a long way to building African infrastructure and improving their quality of life, as well as preparing for, if a large natural component exists, the inevitable effects of natural climate change in areas sensitive to sea level rise such as Bangladesh. (Historically, there have been many beneficial effects to currently underdeveloped regions during past climate optimums as well, but the effect of sea level rise in Bangladesh would be particularly catastrophic) 

You are talking about getting more people stuck on fossil fuels and dependent on technology that functions only with fossil fuels and maybe nuclear power. Whenever someone says "improving quality of life" it seems to relate to the good quality of life as understood by Americans or Europeans. This is unsustainable. It will be better for a few decades and then it will be worse than now. Some areas on this planet cannot support many humans and in some of those places it will get worse. People will have to move. Better do nothing? I don't know. I am glad though that I am not in power to make such big decisions.

If burning fossil fuels is dangerous locally (your closed garage, your town, your country) and maybe globally AND if it results in a boost in population in places that cannot support this population without fossil fuels AND if fossil fuels are non-renewable, will not be affordable in a few decades (give or take a few), and there is no true replacement in sight, it seems to be reasonable to stop using them and unreasonable to worry about money and the end of development for some places. Development will stop in some places in any case. The artificial boost (based on cheap fossil fuels) some areas have experienced will not continue forever. Either because we will focus on the transition into the age of no fossil fuels at home or because we will run out of fossil fuels. Whichever comes first. One's own survival is often expensive for others.



 

Offline frethack

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« Reply #8 on: 07/08/2009 14:15:13 »
Quote
We cannot SUSTAIN our energy needs or life style without fossil fuels. The transition may be smooth if we begin now but as much as I would LOVE to see people beginning to live in ways that are sustainable, I fear that the transition will be rather rough, maybe even terrible.

I still dont think that there is disagreement between us.  There will come a time, possibly in the next century, when fossil fuels will no longer be a necessity to create energy, but for the foreseeable future they will remain our staple energy source.

Quote
Whenever someone says "improving quality of life" it seems to relate to the good quality of life as understood by Americans or Europeans.

I am certainly not advocating a "Western" way of life for any other culture.  When I say "improving quality of life" I mean providing means for clean drinking water to villages, sustainable food production, reducing the occurrence of malaria, and drastically slowing the spread of HIV.

Quote
People will have to move.
Quote
...it seems to be reasonable to stop using them and unreasonable to worry about money and the end of development for some places.


You are correct...people will have to move.  This costs money...money that poor populations do not have.  Bangladesh will also have to build a series of dikes and levees to prevent much of their coastal land from flooding entirely (millions of people live on this land and there is no room for them to just pick up and move).  This will also cost money that they do not have...and will take time to build.
« Last Edit: 07/08/2009 14:41:54 by frethack »
 

Offline Karsten

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What proportion of global warming is attributable to humans?
« Reply #9 on: 10/08/2009 05:19:14 »
You are certainly much more positive and optimistic than I am. We both agree that fossil fuels will not be used in the future. I just think that without fossil fuels as the convenient source for energy and resource for petrochemicals we will not be able to create as much energy as we are now. Cleaner forms of energy, energy factories, and many materials that are needed to create them and maintain them are not possible without fossil fuels.
So, while I can see the need for all those things you mention, I doubt that the energy for it will be there. Our technological abilities will be much less in the future. "Less" in the sense of "powerful". What do you do if you cannot operate large construction machines any longer? What do you do without concrete, steel, copper, glass, etc.? How do you maintain nuclear/water/solar/wind power plants without concrete or steel? How do you feed a world population when the industrial food production depends on oil to such a large extend? There are so many things we cannot do with electricity alone. Right now we cannot even make electricity with electricity alone at a large scale. And while we will one day have to learn how to do this (and I wish we would begin now while we still have the luxury of fossil fuels available), I fear that the areas that are not great for humans now will be worse in the future no matter what we do now. Water purification plants are a good thing. I have the feeling though that they would be constructed using fossil fuels and could not be repaired any longer in, say, 50 years. Same for levees and dikes. And this is assuming we can create food for 8 billion people without fossil fuels, the machines it operates and the fertilizers it allows us to create. Without the food we do not need to worry about the safety of large cities.

... for the foreseeable future [fossil fuels] will remain our staple energy source.
I am pretty sure that we will experience the decline of cheap fossil fuels at a significant level soon. One might say that we are already experiencing it if one looks at the high oil prices despite the fact that we are in a global economic recession and the oil producing countries WANT us to buy it. Just wait what happens when we feel good about our economy again. I would not rely that fossil fuels will be available as a "stable" energy source at all. But that depends on what you mean by "foreseeable". ;)
 

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« Reply #10 on: 07/09/2009 06:41:19 »
The one ace in the hole, technologically speaking, regarding the problems associated with fossil-fuel energy, is nuclear. It is by far the most capable alternative technology. The big obstacle is the waste problem, but that can be largely eliminated by using breeder technology and re-using the waste plutonium to generate more energy. The obstacles to that are chiefly political, not technological.
 

Offline Bored chemist

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« Reply #11 on: 07/09/2009 19:48:00 »
One thing seems to be clear: We are running out of the stuff that may contribute to/cause global climate change. I am afraid the effects of not having fossil fuels any longer will be much more dramatic than global climate change.
You may wish to discuss that with the populations of, for example Bangladesh or Tuvalu.
 

Offline Karsten

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What proportion of global warming is attributable to humans?
« Reply #12 on: 08/09/2009 20:57:27 »
One thing seems to be clear: We are running out of the stuff that may contribute to/cause global climate change. I am afraid the effects of not having fossil fuels any longer will be much more dramatic than global climate change.
You may wish to discuss that with the populations of, for example .

Would a discussion with me change the science or the data or the predictions? Would a discussion change anything for the people who live there? Or would it merely change HOW it is said and how I will FEEL about their predicament? And how would that matter to the people in Bangladesh or Tuvalu?

Some areas will experience global climate change more dramatically (and sooner) than others. Right now we all (or at least some) seem to be searching for (and possibly offering) technology solutions and those solutions all require fossil fuels to come into existence and to function in the future. And now imagine the situation in 30 years with no more fossil fuel powered machines and fossil fuel materials to alleviate the situation. People will (have to) move.
 

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What proportion of global warming is attributable to humans?
« Reply #13 on: 08/09/2009 20:59:05 »
The one ace in the hole, technologically speaking, regarding the problems associated with fossil-fuel energy, is nuclear. It is by far the most capable alternative technology. The big obstacle is the waste problem, but that can be largely eliminated by using breeder technology and re-using the waste plutonium to generate more energy. The obstacles to that are chiefly political, not technological.

You currently cannot build and maintain nuclear power plants without fossil fuels.
 

lyner

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What proportion of global warming is attributable to humans?
« Reply #14 on: 08/09/2009 23:10:10 »
Karsten
Fossil fuels will be available for a long time, yet. the 30 - 40 year oil limit has been the figure which has been quoted for at least the past 30 years as I recall. That would give us 10 -20 years, if it had been correct.
In addition, there is a fantastic amount of coal down there  (decades and decades, I have read). Whatever we do to the atmosphere, we don't really need to think in terms of running out of fuel.

As for who's to blame for the rising temperatures. Even that's not 100% certain. I still think we should assume it's down to us, though.

 

tuttut

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What proportion of global warming is attributable to humans?
« Reply #15 on: 09/09/2009 01:00:45 »
Hasn't this topic strayed from the original question?

The only answer so far that does the job is this by Frethack
"It would be, at this point, impossible to state with any accuracy what the human induced portion of climate change is.  The only accurate statement that can be provided is "less than we thought it was 10 years ago."  "

yes man has contributed to climate change but we don't know the percentages and we will not know them for many years, if at all. What is a concern is that many weather events arebeing blamed on CC/AGW when there is no real evidence. The recent and ongoing fires in the USA and the heat in Australia are being used to promote CC when there is no evidence for it. Yet there is good evidence that it is cyclical. If scientists/weather presenters and the media keep insisting on blaming individual events on CC then many more people are going to become sceptics.

And for those who doubt what effects a degree or two increase in temperature can have, then you only need to look at the heat in Australia to see what 2 degrees above the seasonal average can result in.

As for running out of fossil fuels. This is many years down the line. Even the UK has 100 plus years of coal reserves and they will be mined again once the economy makes it viable. Even if/when we start to run out don't think for one minute thatwe won't start mining and drilling at the poles. The current push toward renewable energy by your local electricity producer has more to do with fooling the green consumer (sucker) than any concern for the environment or their carbon footprint.
 

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What proportion of global warming is attributable to humans?
« Reply #16 on: 12/09/2009 13:20:12 »
As for who's to blame for the rising temperatures. Even that's not 100% certain. I still think we should assume it's down to us, though.

Absolutely!

Global Warming is occurring at this point in our planets history.
There is a grey area about to what degree human activity is responsible for current global climate change.

Therefore, there are four future scenarios:
1. Global Warming isn't predominantly anthropogenic & WE do nothing.
2. Global Warming is    predominantly anthropogenic & WE do nothing.
3. Global Warming isn't predominantly anthropogenic & WE squander our resources.
4. Global Warming is    predominantly anthropogenic & WE seriously tackle it.

I hope it is self-explanatory as to the likely numbers for human mortality & suffering in each case.  So, without wanting to appear callous, the question of risk-versus-resources should be analysed statistically.

So, with present CC-causation models (assuming one doesn't believe that they are a further tool of a green conspiracy) it would seem prudent to assume (as SC infers) that mankind is to blame.  Of course, plenty of (unbiased) funding is needed to improve our climate models and thus, our strategies be reshaped as required. culpability of mankind's influence is revealed as exaggerated.
 

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What proportion of global warming is attributable to humans?
« Reply #17 on: 12/09/2009 14:03:52 »
Additionally, I am compelled to express my belief that not one of us (scientists, engineers or society in general) can afford to wonder blindly into a future of the 'green band-aid' solutions currently being sold to us by our governments or big business every day.

This will lead to an even worse case scenario:
Global Warming HAPPENS & our resources are squandered pretending to fix it.
 

Offline SkepticSam

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What proportion of global warming is attributable to humans?
« Reply #18 on: 12/09/2009 19:39:12 »
Peppercorn:
"This will lead to an even worse case scenario:
Global Warming HAPPENS & our resources are squandered pretending to fix it."

Climate change is happening. Worst case scenario; is it's cyclical and AGW is so insignificant that all our resources and effort were a waste of time.
 

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What proportion of global warming is attributable to humans?
« Reply #19 on: 13/09/2009 00:22:21 »
Peppercorn:
"This will lead to an even worse case scenario:
Global Warming HAPPENS & our resources are squandered pretending to fix it."

Climate change is happening. Worst case scenario; is it's cyclical and AGW is so insignificant that all our resources and effort were a waste of time.
Sorry, my mistake - for the overly literal of you out there - I should have stated 'preventable global warming HAPPENS'. I am in no way claiming that climate change is not happening or that it will not continue to happen (human intervention now can only, at best, limit these effects). I also, personally, would strongly support the proposition that human activity is extremely likely to be the predominant cause of climate change.

SkepticSam - I'm thinking you are claiming (via slightly ambiguous grammar) that human effects on global warming are not an appreciable factor in our climate's current instability.  This is quite a bold claim and I, for one, would be interested to see how you would substantiate it.

Personally, I think it would be lovely if we could say, beyond doubt, that global warming is completely unrelated to human activity; then we could get on with surviving the effects without the worry of trying to fix it.  However, in the world of practical science, the answers are not usually so clear cut.
« Last Edit: 13/09/2009 01:01:49 by peppercorn »
 

Offline SkepticSam

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What proportion of global warming is attributable to humans?
« Reply #20 on: 13/09/2009 23:03:16 »
What I think people need to know, and what the press just can't get right is that there is a difference between a changing climate and (AGW) climate change.

I am all for a nice neat green option, but please don't shove it down my throat with the threat of fines if I don't recycle enough of my household waste.
Don't tell me that we only have 5 years (less than that now) before we reach the tipping point of no return.
Don't show me pictures of ice sheets collapsing and tell me that we can stop this and even maybe reverse it if we cut down on fossil fuel usage.
Don't tell me that we need to get back to CO2 levels of 1990, like it's a magical number whilst giving the air industry longer to reach their level of emissions.
Don't tell me that all disasters :Katrina: LA Fires: Hurricane Activity: Tornado activity and so on are all a result of climate change.

There is far too much that we still don't know. It's only recently that we figured out El Nino and La nina plus other oceanic movements.

Even at this stage we can not say with any certainty that any event is a result of climate change. Why is it that when one region has a statistically cooler yearly temperature that it's just a statistical anomaly and within the range of variation. Yet when the next year there is a warming event it is a result of climate change?

We need honesty, and unfortunately most people get their information from the "popular press". They are well known for publishing half truths or variations to suit the own thinking or that of their readership.

I know that Al Gore, Heidi Cullen and James Hanson, to mention just a few, have been invited to a friendly set of climate discussions and engage in open debate with so called skeptics. They have refused at every invitation. Why?

"What proportion of global warming is attributable to humans?"

We just don't know, but lets not kid ourself that all we need do is "Act on CO2". It's just not that simple.
Take in to account how we have changed the local and global environment by deforestation and covering the area with concrete and tarmac. Our use of domesticated cattle. The way we have changed the course of waterways and our use of dams. Diverting water to deserts (Las Vegas for example) and depriving the areas up stream or up pipe of the water they should have.
And that's just for starters.

And at the end of the day, those that say climate change is mans fault are in a no lose situation. AGW turns out not to be a factor/happening. Well that's because of the action taken as a result of the data presented by climate scientists reversed the situation. AGW is real and we end up screwed, see told you so.

Here are a few links: Nothing heavy or full of science but it may, just may, make you think.

http://www.guardian.co.uk/environment/blog/2009/jun/22/greg-craven-climate-change [nofollow]
http://voices.washingtonpost.com/capitalweathergang/2009/09/a_skeptical_perspective_on_glo.html [nofollow]
http://blogs.chron.com/sciguy/archives/2009/09/the_more_i_study_climate_science_the_more_confused.html [nofollow]
http://www.accuweather.com/video-on-demand.asp?video=37129475001&channel=VBLOG_BASTARDI&title=Debunking%20Global%20Warming%20%20in%20California's%20Wildfires [nofollow]

At the end of the day all most people can do is read and learn. THis should be encouraged, but read from both sides or the argument and don't be fooled by statements that attribute one event or one yearly set of records to AGW climate change.
 

Offline peppercorn

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What proportion of global warming is attributable to humans?
« Reply #21 on: 16/09/2009 17:19:53 »
I am all for a nice neat green option, but please don't shove it down my throat with the threat of fines if I don't recycle enough of my household waste.

I am sorry you equate local government's efforts to enforce recycling policy (in what, I hope, is a fair scheme) with shoving green issues down your throat. Recycling has more to do with good regional-resource management as with fighting global warming.  Also, what is the nice neat green option you are for, if not recycling for example?

Don't tell me that we need to get back to CO2 levels of 1990, like it's a magical number whilst giving the air industry longer to reach their level of emissions.

I agree. Picking an arbitrary year for good CO2 levels is insulting to people.
Yes, it's deplorable to let industries (like air-travel) who can lobby the strongest off the hook.

Don't tell me that all disasters :Katrina: LA Fires: Hurricane Activity: Tornado activity and so on are all a result of climate change.  Even at this stage we can not say with any certainty that any event is a result of climate change. Why is it that when one region has a statistically cooler yearly temperature that it's just a statistical anomaly and within the range of variation.

I don't think anyone here (or, I hope, any politician worth a damn) is trying to claim any of these things. The key point is that there is a finite likelihood of cause and effect (importantly in maths, we can say that the probability of a link is a real number even if the means of calculating it isn't know).  In the case of global climate change there are a number of recognised models which factor in human influences, but none of them claim to be indisputable, just a model of likely outcome.

We need honesty, and unfortunately most people get their information from the "popular press". They are well known for publishing half truths or variations to suit the own thinking or that of their readership.
Again, I agree. If by the "popular press" you mean the tabloids and similarly dumbed down media then the only common motive would seem to be sensationalist reporting (good for punchy headlines) on either side of the argument.


{Al Gore, Heidi Cullen and James Hanson have been invited to climate discussions and engage in open debate with sceptics. They have refused at every invitation. Why?}

Definitely. More rational public debate should be encouraged as a large amount of misconceptions exist of both sides of the argument. I would suspect that a number of valid commentators from both sides have met for public debate over the years, but more needs to be done.

"What proportion of global warming is attributable to humans?"
We just don't know, but lets not kid ourself that all we need do is "Act on CO2". It's just not that simple.

Yes - To assume any fixed point of view is potentially dangerous: "Acting on CO2" & switching brain off.  Deciding it's nothing to do with us & switching brain off is even more so.
« Last Edit: 16/09/2009 17:32:36 by peppercorn »
 

Offline SkepticSam

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« Reply #22 on: 17/09/2009 00:47:11 »
Peppercorn:
I don't have too much free time to go in to detail in my reply, Sorry for that. But I will come back as and when time permits.
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I am sorry you equate local government's efforts to enforce recycling policy (in what, I hope, is a fair scheme) with shoving green issues down your throat. Recycling has more to do with good regional-resource management as with fighting global warming. Also, what is the nice neat green option you are for, if not recycling for example?
Recycling has more to do with local authorities trying to meet governments targets, and governments are trying to meet targets set by Europe. We are not running out of space for landfill, we are running out of licensed landfill sites and space. I have nothing against going green and recycling your household waste but lets start with the manufacurers of what you buy. Do they really need to pack your food with all of that plastic and cardboard? Why do fruit and veg, for example, need all that packaging? And don't mention things like Easter Eggs and other over boxed products. This is where legislation should start.
There is a real danger that there will be a green fatigue and a genuine backlash to being told what we can and can't do, and what action the local, regional and national governments will take against us if we fail to comply.
People mainly react to whats in their pocket. And many people need to see that they are benefitting from the actions forced up on them. Most can not see that the actions they do today will / could benefit their grandchildren. Instead of giving incentives to big industry, why not do little things for the little man? Can we not have a rebate on our council tax or rated depending on the volume by weight that we recycle in our bins?
Then we have the subject of forcing car manufacturers to increase fuel efficency to again save the planet. People don't want to lose their jobs or pay more for their car just because their government tells then what's what. It may seem a cop out but why are these ideas not packaged as a way for "us" to save money. Better fuel efficency means less at the pumps. More nuclear, wind and tidal power will lead to lower energy prices. Not the scare tactics of global warming, much of which is not understood by the public.
Quote
I don't think anyone here (or, I hope, any politician worth a damn) is trying to claim any of these things. The key point is that there is a finite likelihood of cause and effect (importantly in maths, we can say that the probability of a link is a real number even if the means of calculating it isn't know). In the case of global climate change there are a number of recognised models which factor in human influences, but none of them claim to be indisputable, just a model of likely outcome.
Unfortunately, these things are being claimed. It was claimed that the wildfires were a result of global warming. Other instances of claims where single events are a result of global warming. Hurricane Katarina it was claimed caused so much devistation to NO due to global warming. Again this was not true.
 
 

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What proportion of global warming is attributable to humans?
« Reply #23 on: 18/09/2009 12:55:20 »
We are not running out of space for landfill, we are running out of licensed landfill sites and space. I have nothing against going green and recycling your household waste but lets start with the manufacturers of what you buy. ... Can we not have a rebate on our council tax or rated depending on the volume by weight that we recycle in our bins?

Are you seriously suggesting that we should be increasing the number of licensed landfill sites? That's never going to fly.

"lets start with the manufacturers of what you buy" - An excellent point. Legislation should be radically tightened up on packing, as well as "food miles to market". Also, it seems sad that a whole generation has grown up with most not even knowing that fruit & veg is seasonal.  The days of 'anything you want any time you want' are numbered.

Although in a ideal world, we could have recycling-related rebates (or fines - the old carrot or stick argument) to encourage households.  In reality though, can you imagine the increase in fly tipping?

Better fuel efficiency means less at the pumps. More nuclear, wind and tidal power will lead to lower energy prices. Not the scare tactics of global warming, much of which is not understood by the public.

I think the government are wising up to this thought - Their 'Cut CO2' ads show a father who doesn't really care about 'green', but does care about lower bills!
 

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What proportion of global warming is attributable to humans?
« Reply #24 on: 18/09/2009 13:11:46 »
I consider myself an environmentalist.  I am concerned about the amount of pollution we generate, the animals we push to extinction, and the resources we exhaust.  However, I don't believe that we are the driving force behind global warming.  It concerns me that whenever we hear about the effects of global warming, it is always mixed with the message that we are irrevocably destroying the earth.

If our leaders are right about humans being able to counter GW then many less species and habitats will be lost in the long run.


Original question: What proportion of global warming is attributable to humans?

It is likely to be, at least a significant amount (say more than half). It is quite likely to be a majority share. Obviously, terms such as likely & quite likely are problematic - especially as the majority of voters will be inclined to look for any doubt if there is an implied cost involved.
 

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What proportion of global warming is attributable to humans?
« Reply #24 on: 18/09/2009 13:11:46 »

 

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