all 107 comments

[–]KazmarovVeni, vidi, temperaret 27 points28 points ago

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Here's the summary [PDF] of the (gigantic) 2007 IPCC findings, made for politicians. It's nice because it has headlines of each section which are good summaries of the scientific consensus on various aspects of climate change.

Section 1.1 states:

"Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level"

Section 2.4:

"Most of the observed increase in global average temperatures since the mid-20 th century is very likely due to the observed increase in anthropogenic GHG concentrations.

It is likely that there has been significant anthropogenic warming over the past 50 years averaged over each continent (except Antarctica)"

So the evidence for warming of the planet is as strong as scientists can possibly state. The evidence of antropogenic (human-caused) warming is not absolute because there's a lot of variables at play, but it's still pretty damn good.

[–]palanoid 14 points15 points ago*

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If you look at the climate skepticism as phenomenon, it turns out to be very Anglo Saxon phenomena. Study: Poles Apart: the international reporting of climate scepticism

From my European perspective, the question has not been about scientific evidence for long time. It's about politics and PR. Question should be: Why there is controversy and what fuels it?

[–]sailing_the_internet 1 point2 points ago

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The controversy is fueled because global warming was turned into a political issue. This happens all the time. Just look at gay marriage, creationism, welfare, etc. The only reason these are controversial issues is because the state can base policy off them and different people want different things.

Keep in mind that European countries are much smaller than the US. They are closer in size to American states. Viewpoints within a state are much more homogenous than viewpoints across America, thus issues within a state are not nearly so polarizing as country wide issues. I imagine that for European countries, the larger controversial issues spring from policy dictated by the EU.

[–]palanoid 0 points1 point ago

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Then what explains Britain?

[–]greysands 2 points3 points ago

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Perhaps because the usual solution for climate change is a restructuring of energy consumption away from gas/oil. This makes the US unhappy, and an unhappy US is no good for the UK; the US accounts for the UK's largest single export market, buying $57 billion worth of British goods in 2007. (http://en.wikipedia.org/wiki/United_Kingdom%E2%80%93United_States_relations#Trade_and_investment). This would make sense since China, the other mass consumer of oil, seems about as excited to do something about global warming as the US.

[–]sailing_the_internet 0 points1 point ago

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What do you mean?

[–]palanoid 0 points1 point ago

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The study I quote finds that climate skepticism is Anglo Saxon phenomena. It happens mainly in US and UK.

[–]sailing_the_internet 0 points1 point ago

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Ah, I see... I was trying to answer your question as to why global warming is a controversial issue in the US. The size of a demographic isn't a hard rule, but in general the larger a population the more diverse it is. I would imagine climate change is similarly controversial in the UK because it's a political issue. Maybe there is more of a local divide on that sort of topic in the UK. The article you linked also mentioned that India has a lack of skepticism due to a lack of political influence.

[–]carac 10 points11 points ago

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IPCC has indeed a very good description of the current scientific consensus while on the other side you have just 'myths' that are completely incoherent and often contradict one another - here is a good list of such myths with a good debunking on each one:

http://www.skepticalscience.com/argument.php

[–]dr_gonzo 12 points13 points ago

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The theory that the planet is warming, and human activity is to blame, has been undergoing scientific scrutiny since the 1970s.[0] Since then, thousands of different studies and billions of observations have supported the theory of anthropological global warming. For example, recent observations of polar ice cores demonstrates that earth is undergoing traumatic and abnormal change[1], these observations support the hypothesis that humans are causing the planet to warm. We have many observations on the recent effects of climate change including the effects on plankton and glacial erosion.[2] Scientists test the theory of AGW in small steps, like positing that if the planet has been warming, plankton would be migrating. Climate science is the sum of all kinds of different observations like these.

It's often impossible for scientists to prove causation, but the scientific method allows scientists to draw causative conclusions by allowing a hypothesis to be tested repeatedly. We can't prove directly that gravity is caused by mass, but we have made enough observations on how objects with mass behave that we accept the theory of gravity, and apply it in engineering projects every day.

The same is thing is true of climate change. Scientists have spent decades generating thousands of independent studies on wildlife, our oceans, air, soil, and even snails[3], that confirm a theory that has been under evaluation for decades. Like gravity, AGW is a scientific truth.

It's linked elsewhere in the thread, but the 2007 IPCC report on climate change is a good high level summary of some of the key evidence we have. This article provides a more accesible summary of the same evidence.

Worth noting that climate skeptics often challenge IPCC reports on the grounds that because they are aimed at politicians and policy makers, they're inherently biased. It might be reasonable to reject the policy implications from IPCC, but that's no basis to object to the scientific conclusions summarized an IPCC report. In any case, the evidence that the planet is warming and humans are to blame is pretty overwhelming.

[–]mooli 2 points3 points ago

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The theory that the planet is warming, and human activity is to blame, has been undergoing scientific scrutiny since the 1970s.

I would dispute that phrasing somewhat. It's been subjected to scientific scrutiny since the 19th century, and it took until the 1970's for a broad consensus to emerge that this was indeed likely to be happening, a consensus that has only grown in the subsequent decades. Indeed, it is important to stress that the theory stems from radiative physics, and that the predictions preceded observations by half a century or more.

[–][deleted] 14 points15 points ago

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http://www.youtube.com/user/potholer54?ob=0&feature=results_main#g/c/A4F0994AFB057BB8

I was a strong skeptic (not a denier, but a skeptic) prior to seeing these. Oddly enough, I think I've become a much better scientist and more rational person for having watched most of potholer's videos, so I suggest them to anyone who has the time to spare.

[–]giblet_head 1 point2 points ago

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Thank you for this link I greatly enjoyed this series.

[–]mind_grapes 17 points18 points ago

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I'm not sure what you're asking to see here. There's a clear consensus that human activity is very likely responsible for the majority of warming since the mid-20th century. (Those are carefully chosen words).

If you're uninterested in the actual scientific debate (the "small cadre of climate scientists [who] believe it's not an issue" -- and yes there are some), and you're tired of seeing politicians misrepresent the science, then perhaps you could clarify what you'd like to see discussed.

[–]AngrySkillzz[S] 7 points8 points ago

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Anything as long as people can post the evidence to back it up. If the skeptical climate scientists have meaningful results using reliable methodologies, those would be nice to see as well. The science is the important part here, not the politics.

I realize that the scientific consensus is on anthropogenic climate change, but it's difficult to tell that to politicians and deniers (note the word deniers, not skeptics) when the vast majority of public dialog on the issue is hyperbolic and uncited. It's difficult to wade through the misinformation and actually get to the core scientific findings.

[–]rainfaint 11 points12 points ago

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Correct me if I'm wrong, but it would seem that broad consensus within the scientific community carries more weight than peer review in terms of the actually scientific process. If a skeptic is unconvinced by scientific consensus, what quality and quantity of peer reviewed articles do you think they should be presented with before their continued skepticism requires that they be re-labeled as a denier? If you're looking for "proof" of climate change, a politics-oriented subreddit is probably exactly the opposite of where you should go looking. If, on the other hand you're looking for techniques on how to convince the deniers and the skeptics that global warming is real, I would paraphrase doctor House in saying that, "if deniers could be convinced by science, there wouldn't be any deniers."

[–]AngrySkillzz[S] 5 points6 points ago

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Point taken. I figured it would be a reasonable conversation to have though, since it's an important political issue and the information is often misrepresented or presented in a biased way.

[–]scashman 9 points10 points ago*

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There are three basic questions I see as being most relevant.

  1. Is the earth warming, and if so by how much? Are warming trends going to accelerate, decelerate, or stay constant?

  2. How much of this warming is caused by human activity?

  3. What effects will this warming have on human interests, and on the wider world. Will the sum of effects be a net positive or negative?

Edit:

  1. If climate change is happening (whether caused by humans or not), and if it will have net negative effects, what can be done to slow or reverse it?

[–]celoyd 9 points10 points ago

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Given my answers to these (basically, (1) a lot, (2) most of it, and (3) really bad), I want to move on to a fourth question:

What do we do now?

What are the highest priorities? For example, given that there’s only so much political will at the moment, is it better to concentrate on preparing for climate disasters, or to cut our emissions ASAP? Is geoengineering wise?

[–]Gemini4t 1 point2 points ago

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Could you elaborate on 3? I haven't really seen many arguments about how climate change would actually impact us negatively.

[–]candeewolf 10 points11 points ago

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Rising temperatures and more CO2 impacts biological systems on Earth, which, in turn, will eventually greatly negatively impact humans.

On land, frogs and other animals will not be able to adapt to the rising temperatures (some already can't), and die out. On a broad scale, this allows other animals who might have been in competition or been prey/predators to these animals to either boom in population, or die out as they have no food. Eventually, this leads to food that we eat being decimated. We still rely entirely on farming to eat, and the collapse of biological systems will lead to a collapse for humans. As independent as we have become with technology, we are still deeply connected to biological systems around us.

Secondly, CO2 in the atmosphere is absorbed by the oceans. Its one of the main reasons that we don't see as big of a problem in our atmosphere with CO2. However, the oceans can only hold so much before they are negatively impacted. With rising CO2 levels in the oceans, the pH of the saltwater is growing increasingly acidic. While some larger sea life (mammals, sharks, large fish) could handle these small increases, the smallest life, and the basis for the food chain in the oceans cannot. Plankton and other food for the worlds oceans reacts negatively to the small increases we are seeing and expect to see. Their shells break down as this ocean water become more acidic, leading to a decimation of the population. Once it starts there, it leads up the chain until eventually ocean life is decimated as well. If you want to know how that affects humans, just think of all the seafood we eat.

Additionally, the oceans will get worse at absorbing the CO2 as they take in more and more of it. This will lead to temperatures rising globally at an increased rate than even now. We don't fully know if there is a cap on this effect that can result in a rubber-band-like snapback effect, but do you really want to test whether humans can deal with extremely high temperatures?

Lastly (on this short, generic list), is the issue of rising water levels. Glaciers are indeed melting/receding, and this leads directly to higher global water levels. While this doesn't seem that bad, this can wipe out islands in the Pacific, and decimate the coastal regions of the world. Obviously, some will have their take on how bad that really is when it isn't a major part of the worlds population being affected, but its still a negative impact on humans.

[–]RickRussellTX 0 points1 point ago

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When talking about effects on the ocean, don't forget the problem of methane clathrates. Just a small increase in temperatures at the seabed could result in a massive release of hydrocarbons into the atmosphere.

[–]celoyd 7 points8 points ago*

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Sure. More or less at random, here’s a report from the International Food Policy Research Institute claiming, among other things:

By 2050, the decline in calorie availability will increase child malnutrition by 20 percent relative to a world with no climate change. Climate change will eliminate much of the improvement in child malnourishment levels that would occur with no climate change.

Note that this isn’t a peer-reviewed science paper. But the IFPRI is generally well-regarded, and as far as I know is not considered to have any reason for bias on this particular issue.

Although it’s projected that global warming will lead to more extreme weather, it’s not the dramatic events like hurricanes that have the largest human cost. It’s chronic effects on water supplies, grain agriculture, and the potential for serious disruption of marine food.

It’s often pointed out that warming will open new areas to agriculture. This is true; it will have some significant local benefits. However, it appears that, at the global scale, desertification and increased climate instability will more than cancel them out.

Edit: Wikipedia has an entire article on climate change and argiculture. Looks pretty well cited in parts.

Second edit: Someone downvoted the question! For shame, NeutralPolitics. It was a completely reasonable thing to ask.

[–]Carnivalhalla 1 point2 points ago

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1) Those that forget the past are doomed to repeat it.

Diamond suggested that cannibalism took place on Easter Island after the construction of the Moai contributed to environmental degradation when extreme deforestation destabilized an already precarious ecosystem. [24] Archeological record shows that, by the time of the initial settlement, the island was home to many species of trees, including at least three species which grew up to 50 feet or more: Paschalococos -possibly the largest palm trees in the world at the time, Alphitonia zizyphoides, and Elaeocarpus rarotongensis, as well as at least six species of native land birds. Barbara A. West wrote, "Sometime before the arrival of Europeans on Easter Island, the Rapanui experienced a tremendous upheaval in their social system brought about by a change in their island's ecology... By the time of European arrival in 1722, the island's population had dropped to 2,000 – 3,000 from a high of approximately 15,000 just a century earlier." [25] By that time, 21 species of trees and all species of land birds went extinct through some combination of overharvesting/overhunting, rat predation, and climate change, the island was largely deforested, and it did not have any trees more than 10 feet tall. Loss of large trees meant that residents were no longer able to build seaworthy vessels, significantly diminishing their fishing abilities. This was further exacerbated by the loss of land birds and the collapse in seabird populations. By the 18th century, residents of the island were largely sustained by farming, with domestic chickens as the primary source of protein.

2)more on environmental degradation.

[–]archiesteel 1 point2 points ago

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Skeptical Science has a nice breakdown of the positives and negatives of global warming. It's a sobering read.

[–]scashman 3 points4 points ago

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My understanding is that 1 has a clear answer (yes), two has a more debated but generally accepted answer (a good chunk), and three is a matter of speculation.

I think the question you added is so important that I edited my post to include it.

[–]elphinstone89 0 points1 point ago

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Bear with me on these answers I do not have access to the scientific journals I used to gain this knowledge so I cant be exact.

So question 1, Is the Earth warming, howmuch and at what rate?

Yes it is warming, we can see this by looking at the fossil records, ice cores etc. These show the Earth temperature fluctuates through glacial (ice age) and interglacial (now) periods. The glacial period is the standard period for the Earth and Ice ages last longer the the times between. These temperature shifts take thousands of years, but it does fluctuate up and down during these periods and climate change deniers often point to times when the planet cooled in around the end of the 80s beginning of 90s (I think, cant remember exact dates) to say that its not really happening. However, we are currently warmer than we should be at this point in an interglacial period. Looking at a graph showing global temperatures over a time period of millions of years we can see the increases in temperature from the last 200 years on this graph. (I will try and find the graph and post it later). The rates of change I cant remember off the top of my head but will look it up and add it later.

Question 2. How much is human activity causing it?

So if we look at CO2 in the atmosphere we find a dramatic increase in the last 200 years, since around the time of the start of the industrial revolution. We can match this to a sharp increase in the planets temperature that has been increased since then.

Before Q2 we need a question that you did not ask but many do that is linked to yours is: How do we know CO2 is the cause?

Well for this we can look at pollen records and silt cores that show increases in CO2 correlating with an increase in temperature.

Question 3 I might find hard. Effects on Human interests and the wider world?

Well I have already pointed out the temperature of Earth fluctuates between glacial and interglacial. The base temperature in at a glacial period. One fear of this climate change is that the a new base will be formed at a higher temperature. More pressingly is the matter of water. Water is essential for us to live. If the planet heats up there will be less clean drinking water as the glaciers that hold our water supplys are melting so there is less water for our expanding population. Couple this with the melting of the ice caps and the ice sheets on Greenland, Canada Russia, etc and we get sea levels rising. If this happens many island nations in the Pacific and Indian oceans will be submerged so couple the rising population with decreased water and decreased land.

We also need to talk about the fact that deserts are increasing. Now I cannot remember exactly how this works because I wasnt paying attention in this class but, increasing temperature causes the deserts to expand, this makes it harder to find land to produce food for our growing population.

So to summarise; looking at fossil record, pollen records, icecores etc we can see that the planet is heating up and the the most likely cause is man made CO2. This will effect our drinking water, food supply and cause the oceans to rise.

[–]Deviator77 7 points8 points ago

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You can't blame Al Gore for not backing up his comments. He wrote a book with good, solid data. It was later politicized by opponents.

[–]kethas 4 points5 points ago*

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Edit: The Economist's December 2009 special report covered climate change from numerous angles (the science, the economics of climate change mitigation, the politics and game-theory of a country setting a climate-friendly agenda unilaterally vs. worldwide consensus and enforcement). It's worth reading in its entirety:

http://www.economist.com/specialreports?year[value][year]=2009&category=76984


The Economist had a special report on climate change a few months ago that I thought was very well-written and impartial. It laid out the train of thought behind climate change decisionmaking, something like:

  1. Has the Earth been warming in the past?
  2. If so, was it man-made?
  3. If so, will it continue?
  4. If so, will future warming be a net problem for humanity?
  5. If so, is it within our power to stop or slow future warming?
  6. If so, are the resources required to slow or stop future warming best used to that end, instead of, for example, subsidizing rebuilding efforts farther inland, or researching more heat-resistant crops?
  7. If so, can we trust that climate-preservation efforts on our (e.g. the U.S.) part will be reciprocated by others (e.g. China), instead of them taking our climate preservation efforts as license to continue expanding and polluting, resulting in no long-term reduction in climate change and a loss of relative industrial power on our part?
  8. If so, can we assemble the political will to initiate, and stick to, a climate-preserving agenda?
  9. If so, what's the best such approach?

I'll see if I can find the Economist article.

[–]archiesteel 6 points7 points ago

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Good luck keeping this politically neutral...

[–]AngrySkillzz[S] 7 points8 points ago

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Hopefully if any of them show up they'll live up the the name 'skeptics' and make valid points instead of being straight-up deniers and propagating misinformation. I'll give them the benefit of the doubt.

[–]this_barb -2 points-1 points ago

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Sadly, I'm unwilling to accept random faceless Redditors as skeptics. Either they preface their retorts with their academic history in climate science or they don't respond at all.

[–]dr_gonzo 6 points7 points ago

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I'm not sure why you got downvoted for pointing this out. Maybe people didn't follow your link.

This practice of spamming another subreddit from a clique subreddit is pretty obnoxious, and I wish people pointed out more often when this was happening. (Even better, I wish comments and submissions had trackbacks to other reddits.)

[–]archiesteel 2 points3 points ago

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I'm not sure why you got downvoted for pointing this out. Maybe people didn't follow your link.

Rather, I got here before the folks at /r/climateskeptics did, and they're voting me down out of spite.

[–]RAPES_GRAPES 0 points1 point ago

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I think the most interesting question is cross-disciplinary with a large economic component. Namely, what is the optimal amount of resources to be allocated to reduce AGW?

Meta-complaint: Saying that "the general consensus is X" without proof is an appeal to authority, and really the writer's credibility in my eyes. When making an assertion believed to be common knowledge, please simply state it.

[–]Kar98 0 points1 point ago

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There is a good set of videos by a BBC journalist here: http://www.youtube.com/user/potholer54?ob=4#p/c/A4F0994AFB057BB8

[–]Will_Power -4 points-3 points ago

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I am a skeptic, and here's a brief list of items that summarize my position:

  • CO2 is a greenhouse gas. This is not disputed.

  • A doubling of atmospheric CO2 from preindustrial levels (i.e., from 280 ppm to 560 ppm) will increase mean global temperature by about 1°C. This is rarely disputed.

  • Estimates for climate sensitivity (how feedbacks from the original CO2 radiative forcing) are all over the place, but the figure one most often hears from warmists is 3°C per doubling. There is no consensus on this point.

  • IPCC scenarios that suggest more than 560 ppm atmospheric CO2 do not take into consideration physical limits to extraction of fossil fuels at all.

As to the original question, both sides have some things right, but grounds for alarming predictions are incredibly thin.

[–]archiesteel 8 points9 points ago

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Estimates for climate sensitivity (how feedbacks from the original CO2 radiative forcing) are all over the place, but the figure one most often hears from warmists is 3°C per doubling. There is no consensus on this point.

"Warmist" is a politically-charged word.

There is quite a bit of support for a 3C climate sensitivity, both from models and from observatins.. James Annan made a great case for the figure:

http://julesandjames.blogspot.com/2006/03/climate-sensitivity-is-3c.html

The fact there may not be a consensus is exactly why the value is estimated to be between 2 and 4.5C. The 3C value is the best guess, but it could be lower or higher, which is why AGW is a real threat.

As for not having enough fossil fuels to go beyond 560ppm, I have yet to see a comprehensive, evidence-supported study that confirms this. I think it's quite optimistic, given the huge reserves in Canada's oil sands, as well as the US' vast reserves of natural gas. If you have links to peer-reviewed study about this I'd be interested in reading it.

In any case, the point you bring up tends to suggest transitioning away from fossil fuel is a necessity due to other factors (in this case, Peak Oil). This means that, following your logic, whether or not AGW is real the result is the same: we need to move on from fossil fuels. Opposing AGW theory then becomes rather pointless, doesn't it?

[–][deleted] ago

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[deleted]

[–]KazmarovVeni, vidi, temperaret[M] 2 points3 points ago

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Not in this thread. Have your pissing contest elsewhere.

[–]Will_Power -3 points-2 points ago

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Fair enough. I'll delete that comment. I've responded to the rest of his post in another comment.

[–]Will_Power -4 points-3 points ago

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The fact there may not be a consensus is exactly why the value is estimated to be between 2 and 4.5C. The 3C value is the best guess, but it could be lower or higher, which is why AGW is a real threat.

Please see the following comment where I discuss why the 3°C figure is too high:

http://www.reddit.com/r/climateskeptics/comments/q5el3/steven_hayward_why_the_climate_skeptics_are/c3uz6l2

As for not having enough fossil fuels to go beyond 560ppm, I have yet to see a comprehensive, evidence-supported study that confirms this.

I cite several in this post: http://www.reddit.com/r/climateskeptics/comments/mkg1w/fossil_fuel_limitations_to_carbon_emissions/

This means that, following your logic, whether or not AGW is real the result is the same: we need to move on from fossil fuels.

Yes. I've always said so.

Opposing AGW theory then becomes rather pointless, doesn't it?

No, because I believe in maintaining integrity in science. I'm not an "ends justify the means" kind of guy. (I'm not implying others feel differently, by the way.)

[–]stronimo 6 points7 points ago*

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I've downvoted you. I wouldn't regards links to your own comments in other subreddits as evidence of anything.

[–]Will_Power -1 points0 points ago

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Did you read the links?

Is it preferable to copy/paste portions of comments in this subreddit? (Honest question.)

[–]stronimo 3 points4 points ago*

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Wall of text copy-pasta isn't evidence, either. Show us your impartial sources, preferably peer-reviewed academic sources, but well-written new articles are fine, too. Wikipedia isn't acceptable.

See the FAQ.

[–]KazmarovVeni, vidi, temperaret[M] 2 points3 points ago

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Please let us moderators instruct members as to what is and what is not acceptable.

[–]Will_Power -1 points0 points ago

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Please follow my second link. I cite three peer-reviewed papers with links to several more in that post.

[–]archiesteel 6 points7 points ago*

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Please see the following comment where I discuss why the 3°C figure is too high

I'm not interested in going to re-read climateskeptics threads, but I did check that one to humor your. Unfortunately, you discuss it, but you don't present any actual evidence that 3C is too high, or that the methodologies are wrong. All you seem to do is disagree about the right-hand tails and such.

The fact of the matter is that, when doing a survey of various climate sensitivity values (and not just looking at the ones that indicate a low sensitivity), the best guess is still 2 to 4.5C, with a likeliest value of 3C.

I cite several in this post:

Many of these seem to be behind paywalls.

No, because I believe in maintaining integrity in science.

Well, in this case it's both, because the current state of the science is that climate sensitivity is about 3C. Now you may not like this, but until you come up with actual peer-reviewed papers supporting your position I'm going to go with the currently accepted CS value, as uncertain as it may be (even with your best intentions, you are not a climate scientist, and your claims have not been reviewed by scientists - in fact, the only climate scientist in /r/climateskeptics, counters, does offer a convincing rebuttal to your claims in that first link you gave).

So, unless you can show me conclusive evidence that, when one considers all lines of evidence (and peer-reviewed articles on the subject), the likeliest value for CS is between 2 and 4.5C, with a best guess at 3C. Sure, it's a guess, but right now there's no reason to be certain it will be under this - if we can't be certain, then we simply can't take chances (especially when you already agree about what must be done).

Further arguments in favor of a 3C sensitivity can be found here, for the people here who might be interested in learning more about the science:

http://www.skepticalscience.com/climate-sensitivity-advanced.htm

[–]nuclear_is_good 7 points8 points ago

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A doubling of atmospheric CO2 from preindustrial levels (i.e., from 280 ppm to 560 ppm) will increase mean global temperature by about 1°C. This is rarely disputed.

This is just a "lie by omission" - that is what would take place in an imaginary world with zero water vapor.

The actual scientific consensus is that the overall short-term sensitivity is in the range of 3C for a CO2 doubling. The long-term sensitivity when including albedo changes from ice loss could reach a value as high as 6.

To this date the only peer-reviewed papers suggesting unexpected negative feedback have been Lindzen2009, Spencer2011 and Lindzen2011 - all very weak papers based on just cherry-picking special intervals and partial data on the amount of heat in the ocean, and which have been all addressed in many peer-reviewed papers (and in the case of Spencer2011 have also resulted in the resignation of the editor accepting that paper).

[–]Will_Power -2 points-1 points ago

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You need to look up the definition of consensus.

[–]archiesteel 6 points7 points ago

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The consensus isn't that Climate Sensitivity is 3C, rather that CS is very likely to be within 2 and 4.5C, with the "best guess" being 3C.

Now, you may claim that some studies show a lower value (though those that show a lower value than 1.5C, including Lindzen's and Spencer's, have indeed be shown to have severe shortcomings), and that's legitimate, however there are studies that show higher values. This is how the 2 to 4.5C range has been determined, considering the various lines of evidence (both from models and observations) regarding climate sensitivity.

Now, you could very well be right, and CS could be slightly lower than 2C (or even 1.5C, though that seems extremely unlikely). However, it could also be higher than 4.5C (though again unlikely), which means that it could be anything from "unpleasant" to "very bad". It is precisely this uncertainty which means we must start making efforts to mitigate the threat and transition away from fossil fuels (preferably to renewables, though there's a case to be made for some nuclear as well, if Thorium reactors reach the required level of maturity and solve the remaining problems with new reactor designs).

[–]nuclear_is_good 2 points3 points ago

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[–]Will_Power -1 points0 points ago

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Agreed, but to claim consensus for 3°C as the best estimate for climate sensitivity is false.

[–]nuclear_is_good 2 points3 points ago

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Maybe I should have mentioned the range, but (since that is a lognormal) it would have suggested a mean higher than 3 which is the median (for which is a consensus). The IPCC graph would have been the easiest thing to 'say' :)