Arctic Ice Loss Driven By Natural Swings, Not Just Mankind, Says Study (reuters.com)

Alister Doyle, reporting for Reuters: Natural swings in the Arctic climate have caused up to half the precipitous losses of sea ice around the North Pole in recent decades, with the rest driven by man-made global warming, scientists said on Monday. The study indicates that an ice-free Arctic Ocean, often feared to be just years away, in one of the starkest signs of man-made global warming, could be delayed if nature swings back to a cooler mode. Natural variations in the Arctic climate "may be responsible for about 30-50 percent of the overall decline in September sea ice since 1979," the U.S.-based team of scientists wrote in the journal Nature Climate Change. Sea ice has shrunk steadily and hit a record low in September 2012 -- late summer in the Arctic -- in satellite records dating back to 1979. The ice is now around the smallest for mid-March, rivaling winter lows set in 2016 and 2015. The study, separating man-made from natural influences in the Arctic atmospheric circulation, said that a decades-long natural warming of the Arctic climate might be tied to shifts as far away as the tropical Pacific Ocean.

Comments

I smell a rat...or alternative facts

[passionplay]

Why does it take 37 years to show nature is responsible? Something doesn't smell right.

Re:I smell a rat...or alternative facts

[Khashishi]

Nature is responsible for 30-50%. That still leaves 50-70% responsibility to mankind.

Re:I smell a rat...or alternative facts

[Dr_Terminus]

Just a bad summary... this article is better: https://www.sciencedaily.com/r...

"Anthropogenic forcing is still dominant -- it's still the key player," said first author Qinghua Ding, a climate scientist at the University of California Santa Barbara who holds an affiliate position at the UW, where he began the work as a research scientist in the UW's Applied Physics Laboratory. "But we found that natural variability has helped to accelerate this melting, especially over the past 20 years." ...

"In the long term, say 50 to 100 years, the natural internal variability will be overwhelmed by increasing greenhouse gases," Ding said. "But to predict what will happen in the next few decades, we need to understand both parts."

Re:I smell a rat...or alternative facts

[Gadget_Guy]

Guestimation of ranges based on no science what-so-ever. Good one.

What? It's based on the study that is being discussed here. Based on the article, I don't have enough details about the study to find how they came up with those figures, but neither do you have enough information to say that it was based on "no science what-so-ever".

Re: I smell a rat...or alternative facts

[NatasRevol]

I think you mean arguing against facts, because that's all that xkcd comic was. Which sounds exactly like something an anonymous coward would do.

Re:I smell a rat...or alternative facts

[khallow]

Sorry. We just can't muster the energy to effect climactic changes on that scale, short of having a Nuclear War.

A nuclear war doesn't involve that much energy either. Every bit of heat generated on Earth's surface is radiated to space in short order. I would guess within a couple of weeks. We don't freeze to death because solar power and to a much lesser extent geothermal heat continues to heat the surface of Earth.

What increased levels of CO2 change is the amount of infrared frequency heat radiated to space. This is why the "greenhouse effect" got its name. CO2 and a number of other "greenhouse gases" are transparent at visual light frequencies, the peak energy frequencies of solar energy hitting Earth, but more opaque to the infra-red frequencies, which are the peak energy frequencies of heat on Earth radiated to space. So more CO2 means that some heat is absorbed by the atmosphere instead of being radiated to space. That is the mechanism of global warming.

As I recall, the amount of heating at present levels of CO2 concentrations in the atmosphere is thought to be 1.5 C per doubling of CO2. As you may notice, this is far from the IPCC's claimed 3 C per doubling of CO2 in long term heating. That is based on assumptions about positive feedback effects which the IPCC has yet to fully demonstrate (though two commonly mentioned mechanisms are reduced snow cover (which reduces the Earth's albedo at mid to high latitudes) and methane release from warming tundra and clathrate deposits in oceans).

So to summarize, global warming is not due to human activity directly heating the Earth. Instead, it's due to CO2 and similar gases hindering the cooling of Earth as well as significant alleged positive feedback. Humans produce a lot of those gases, and unlike most of the natural processes, it's a large net release with a slightly different isotope mix than decaying plant matter. So we do have a significant increase in the last couple of centuries in CO2 with some supporting evidence that it is mostly due to human activity.

We also have some crude radiative models that explain most of the current warming by themselves. So it is not a stretch to say that we have evidence that human activity is responsible for at least a significant portion of current warming, perhaps even most of it.

Re:I smell a rat...or alternative facts

[Namarrgon]

See here.

Re:I smell a rat...or alternative facts

[Gadget_Guy]

The article doesn't need to prove anything, other than cite the study, because it isn't science. It is just news about the science. I am sure that the study itself, which was made by scientists and published in a scientific journal, would actually show their workings; otherwise they would not get published. But the fact that we haven't seen the study is not itself evidence that the figures were based on "no science what-so-ever".

If you walk into a room with your eyes closed, you cannot definitively say that there isn't a red ball in the room. All you can say is that you can't see a red ball. Similarly, if you haven't read the paper, you can't say that the percentages are unproven. All you can say is that you haven't seen the proof.

Should the original poster have read the study before discussing the percentages? If this were an academic discussion or an official policy document then absolutely. But this is just a forum on the internet, occupied by deniers who make no effort to prove their own claims. Regurgitating figures from the article is a step up for a lot of people around here who never get past reading the headlines.

Scary stuff

[reginaldo]

I have some future oceanfront property in Kansas if anyone is looking. One question I have is: At what point does global warming become so evident that there is no more argument as to whether it is occurring, and the argument becomes what do we do about it? I'm pretty sure we should already be there, but we aren't.

Re:Scary stuff

[SpankiMonki]

what do we do about it?

Move to higher ground.

Re:Scary stuff

[Computershack]

One question I have is: At what point does global warming become so evident that there is no more argument as to whether it is occurring, and the argument becomes what do we do about it? I'm pretty sure we should already be there, but we aren't.

Harldy anyone disputes the fact there is global warming. The dispute is over how much of it we're causing and whether or not its actually abnormal given that in the history of the planet it has been far warmer many many times over the millennia. Then there's what we should do about it and given how almost every other month something new is being found out about our climate and what affects it I hardly think we're in a position to be deliberately messing about with it. Sure reduce/eliminate what we put in the air etc but when you start doing things like schemes to reflect the sun, artificially forcing rain etc then we may find we're doing more harm than good.

Re:Scary stuff

[Rob Y.]

How about a partial solution (increased efficiency) that would be relatively painless while there are still low-hanging SUV's to be picked, and might buy us some time to figure out how to really solve the problem without bouncing us into the dark ages? Nobody's saying to simply stop using fossil fuels right now - but certainly we can use less of them - and pollute the environment less while doing it. But of course, folks like you will raise red herrings about the dark ages as an excuse to do nothing. So why would you want to do nothing, again? Is your last name Koch? Why would even Koch want to do nothing, come to think of it...

Re:Scary stuff

[beelsebob]

I mean, there are plenty of bits of progress that don't take us back to the dark ages being proposed.

For example, lets invest heavily in solar, wind and nuclear power.

Even those are opposed by the coal/oil drilling nut jobs.

Re:Scary stuff

[Archangel Michael]

certainly we can use less of them

I can't tell you how many liberals I know use Amazon Delivery for something they forgot at the store ... because they are too lazy and can't wait till the next time they drive by.

Rich Liberals who love to tell us the world is burning/melting because of AGW, but still fly around the world on private jets to private islands and gated communities, who arrive in three car SUV entourages.

The only authentic liberal I know of is Ed Begley, who lives like he preaches. I don't agree with him on much, but at least he does what he says.

Re:Scary stuff

[demonlapin]

FWIW, air conditioning in hot climates is substantially less energy-intensive than heating in cold ones.

Re:Scary stuff

[Vrekais]

Delivery is a red herring though, having items delivered is likely a more efficient use of fuel than using a car to get items for single household. A delivery driver can server a 1 or 2 dozen families a day for approximately 6-7 hours of driving. If at a low estimate 12 families instead drove themselves to the shop (or possibly several shops) with an average round trip of an hour that's already more fuel burned and 12 times as much traffic capacity taken up. I don't have a car though so delivery is often a necessity for me, there's a limit to what I can carry.

I agree that people can be lazy and after instant gratification, and the SUV fashion is getting out of hand considering how often I see them being driven as a daily commuter vehicle with a single occupant.

Re:Scary stuff

[Penguinisto]

Delivery is a red herring though, having items delivered is likely a more efficient use of fuel than using a car to get items for single household.

Where I live, population density is 14/sq mi. It's more efficient in my case to drive into town once a month or so in a larger vehicle, load up on everything I need for the month, come back, and not burn any fuel after that (I work remotely). If I missed something, I do without it until the next time I go out (barring actual emergencies, e.g. a suddenly dead well pump or a solar inverter that goes on the fritz, though I do keep spares on-hand for both).

In GP's assertion, a 1 lb. item burns an impressive amount of fuel-per-pound for that UPS/FedEx/Whatever truck if it's just the one item, even if the truck were to only go a block out of its way... even worse when its cumulative, which was his point.

PS: I don't own an SUV.

Re:Scary stuff

[khallow]

They all like to disguise the argument "we do nothing, and fuck everyone that isn't me" as "well, the evidence really isn't very strong, I mean, I'm not convinced it's really happening"

I agree those people exist. But we also have people who want to fuck over billions of people to show how much they care about the environment. Those people tend to wax poetic about how much future harm they're supposedly preventing.

Re:Scary stuff

[neilo_1701D]

I mean, there are plenty of bits of progress that don't take us back to the dark ages being proposed.

For example, lets invest heavily in solar, wind and nuclear power.

Even those are opposed by the coal/oil drilling nut jobs.

Q: What did South Australia have before candles?

A: Electricity.

Have a look at the South Australian experiment in renewable energy: http://search.abc.net.au/s/sea...

Re:Scary stuff

[ThosLives]

I think the bigger issue is that some people can sacrifice basically their entire standard of living and it still won't guarantee a particular outcome. And this isn't even on the backs of the "wealthy fossil fuel barons" - this is just the average everyday person.

So it boils down to "absolutely everyone must do something" and the backlash of "who are you to tell me what I should do."

So then you get into "since everyone isn't doing it, I'm not going to sacrifice..." and nothing happens. Basically you have to accept forced behaviors or penalties - which a substantial portion of the population (not just in the US, by the way) takes issue with.

Re:Scary stuff

[narf0708]

propose a solution that doesn't bounce us into the dark ages please.

Nuclear energy. It's clean, it's safe, and it would be cheap if it weren't for paranoid over-regulation. Yes, some safety regulation is needed, but the nuclear industry has far more than it needs, which only restricts its much needed development.

Re:Scary stuff

[Koby77]

That XKCD comic WOULD be very scary, if it was accurate. But it is not. The hockey stick runaway temperatures since 1900 never happened.

http://notrickszone.com/2017/0...

Re:Scary stuff

[Orgasmatron]

Did you not notice that the hockey stick nearly disappeared a some years ago? One day, it was everywhere you looked. Now you rarely see it except in deep disguise, like that comic strip turned sideways.

That's because a couple of statisticians disproved it, back in like 2003 or so. And by "disproved it", I mean into tiny pieces that were then burned and the ashes dropped into a volcano. Several members of the Hockey Team (their term for themselves) then destroyed what was left of their credibility by attempting to un-disprove it

Climate "science" is, apparently, done by guys that sorta half remember the one stats course they took in high school. Every time you look around these days, you find that someone else with a post-secondary knowledge of statistics has peeled back another sheet of faux-brick wallpaper they've been using to make their styrofoam outhouse look like a stone castle. See, Patrick Frank for an excellent example. Or click around a bit on this site to see what the Statistician to the Stars has to say.

Re:Scary stuff

[tbannist]

Did you not notice that the hockey stick nearly disappeared a some years ago?

No, actually I didn't really. You might not see it because "climate skeptics" have largely conceded that the fight against the Hockey Stick has been resoundingly lost. If your main sources of information on climate science disagree with the consensus, they are naturally going to avoid reminding you that they resoundingly lost that battle.

One day, it was everywhere you looked. Now you rarely see it except in deep disguise, like that comic strip turned sideways.

Wait. You think "deep disguise" is rotating something 90 degrees?

That's because a couple of statisticians disproved it, back in like 2003 or so. And by "disproved it", I mean into tiny pieces that were then burned and the ashes dropped into a volcano.

Actually, Steve McIntyre and Ross McKitrick showed that the statistical methods used were not the best methods and that the choice of methods contributed a small bias to the graph. The graphs were redone with different methods and the results were almost identical. From Wikipedia:

More than two dozen reconstructions, using various statistical methods and combinations of proxy records, have supported the broad consensus shown in the original 1998 hockey-stick graph, with variations in how flat the pre-20th century "shaft" appears. The 2007 IPCC Fourth Assessment Report cited 14 reconstructions, 10 of which covered 1,000 years or longer, to support its strengthened conclusion that it was likely that Northern Hemisphere temperatures during the 20th century were the highest in at least the past 1,300 years. Over a dozen subsequent reconstructions, including Mann et al. 2008 and PAGES 2k Consortium 2013, have supported these general conclusions.

If I'm reading that correctly, the Hockey Stick graph has been re-affirmed and shown to be essentially correct by no less than 26 subsequent papers from a variety of authors, using a variety of data sources and statistical methods. On the other hand, the number of papers that did the research and didn't get a hockey stick graph appears to be zero.

I guess that means your position has been cut into "tiny pieces that were then burned and the ashes dropped into a volcano."

We know this, everyone in the world says.

[Anonymous Coward]

The natural swings are evident with the seasons, periodic shifts based on geo-solar geometry, probably sun cycles and everything else in the universe - *BUT the base/background temperature before those variations *IS* increasing *AS* we have measured C02 and greenhouse insulating gases, methane etc, reaching historic (in paleological terms, during all of human civilization and a long time before that, millions of years) proportions of our atmosphere. We know we've caused some acidifying of the oceans, which with warming dissolves further frozen/captured methane and such gasses at the bottom of the ocean and brings that into our atmosphere in a positive feedback loop which we can never control...

What of this one study exonerates BILLIONS of tailpipes in the world and TRILLIONS of tons of coal burned ongoing? None of it.

But watch them try to run with this deliberate, intentional misunderstanding of what actually was confirmed by this study. Watch and see.

Re:We know this, everyone in the world says.

[reginaldo]

I agree. This is something of a glass-half-full study. So 30-50% of arctic ice cap melt is natural. What of the other 50-70%? It is already misunderstood. It's interesting how different media sources are covering this study: http://www.dailymail.co.uk/sci...

percentages

[OlRickDawson]

Finally a study that shows percentages.The politicals have have claimed that climate change is either 100% man-made or 100% natural, depending upon which side of the argument they were on. Reasonable people knew that it had to be a bit of both, but there never seemed to be any studies that showed what the percentages of each it was.

Re: percentages

[Anonymous Coward]

People don't understand distributions. It has to either be all or nothing. If humans contribute 40% to global warming and nature contributes 60%, the majority of people will fall into "well nature is doing it too" BS, deflecting the significance of their own contribution.

I'm all for honest reporting but I don't trust trust the average US citizen for reading, interpreting, and reacting to study results--nor do I trust media outlets with agendas that could care less about the environment. I can see the Fox headlines now "Nature contributes 60% of global warming, Obama cover up to kill coal" never discussing the significance of the other 40% side of the story.

Re:percentages

[quantaman]

Finally a study that shows percentages.The politicals have have claimed that climate change is either 100% man-made or 100% natural, depending upon which side of the argument they were on. Reasonable people knew that it had to be a bit of both, but there never seemed to be any studies that showed what the percentages of each it was.

Globally almost 100% man-made is accurate because natural climate variations simply aren't that fast enough to be a big contributor.

However, local climates are more variable, particularly the Arctic, so percentages come into play. From the article it sounds like previous research simply didn't have enough data to make useful percentage estimates.

Snow storm?

[number6x]

Very low rates of commenting today. Could it be the blizzard on the east coast keeping everyone busy?

Good to see it's not all robots posting here.

Back on topic, it's an interesting read. 30-50% may be natural climate trend and the rest man made (50-70%) man made.

It may be good science, but showing 50-70% man made probably won't go down well with the current administration. <sarcasm> Prepare to have the budget cut for this "U.S.-based team of scientists", unless they get their alt-facts corrected.</sarcasm>

Re:Snow storm?

[Midnight_Falcon]

I'm pretty sure I learned in high school (graduated 2002) in Earth Science (1998, freshman year) that global warming was part of a tropical age-ice age cycle, an ice age being defined as there being ice at the poles of the Earth. That said, I was also taught that climate change is due to greenhouse gases etc causing this to accelerate far faster than the historical record for transition into a tropical age.

So, I don't know what's new about this theory aside from the fact it can be diced up into "alternative facts" that say hey! look! climate change (somewhat) natural! ... but we've known all along manmade climate change is most of the problem.

Re:Snow storm?

[number6x]

Great comment.

I think a lot of the scientific debate has been about the models that project the changes into the future. I'm amazed at how accurate the Shell Oil researchers were with their predictions.

Re: Snow storm?

[orlanz]

I was thinking that a 20% uncertainty was kind of shitty. They could have said 30% natural, 50% man made, and 20% unknown. That's pretty bad for an analysis.

Re:Snow storm?

[cbeaudry]

The problem is you graduated in 2002. If you had graduated in 1972, this propaganda had not yet been introduced to the education system.

Re:Snow storm?

[phlinn]

I wonder if the previous post was thinking of Marcott's statement about the paper rather than the paper itself. "Our global paleotemperature reconstruction includes a so-called “uptick” in temperatures during the 20th-century. However, in the paper we make the point that this particular feature is of shorter duration than the inherent smoothing in our statistical averaging procedure, and that it is based on only a few available paleo-reconstructions of the type we used. Thus, the 20th century portion of our paleotemperature stack is not statistically robust, cannot be considered representative of global temperature changes, and therefore is not the basis of any of our conclusions. "

not alt-facts, just a reasonable statement.

[number6x]

Read the article...

30-50% of the warming is due to natural, not man made, effects.

Or, as scientists have been saying for decades, the majority of the warming (50 - 70%) is due to man made effects.

This includes scientists at shell oil and Exxon-Mobil. I remember debate class in high school, fall of 1979, our team was 'pro' nuclear power. We used research from oil companies about the dangers of global warming as one one the arguments in favor of expanding nuclear power use. We won the debate, despite the fact that the 3 mile island accident happened in spring of '79. That made it a very tough debate to win the pro nuclear side of the argument.

Re: not alt-facts, just a reasonable statement.

[Immerman]

Not hardly.

Picture a gerbil in a ball running back and forth up the slopes of a skateboarder's half-pipe - that's your "natural contributions" - there is no steady long-term push in either direction, at worst you get a few decades or centuries of climate anomalies before whatever forcing factor is causing it subsides. The gerbil's never going to be able to make it up that slope.

Now picture what happens if you start building a bunch of fans or something that blow up one side of the half-pipe hard enough to push the ball 70% of the way up the slope. That's the human contribution, and the gerbil is now going to be able to get a *lot* further up the slope than it would on it's own.

And if you keep adding more fans, and the wind-assisted gerbil manages to make it to the top? Well that's the tipping point - the climate enters a runaway greenhouse process, as it has many times in the past, and we leave the ice age that has gripped the planet for the entire history of our species and transition over the course of a few millenia to a tropical/desert "warm Earth" state, as it has many times in the past. And that transition period is going to be a bitch.

Direct link to paper

[Namarrgon]

Ding Q, J. M. Wallace, D. S. Battisti, E. J. Steig, A. J. E. Gallant, H. J. Ki, L Geng: Tropical forcing of the recent rapid Arctic warming in northeastern Canada and Greenland, [PDF] Nature, 509, 209-212, (2014)

Re:Direct link to paper

[the phantom]

This is not the paper described in the summary, but rather an older paper with some of the same authors. The paper referenced in the summary was published online yesterday in Nature Climate Change. I'm sorry that I can't give a direct link to a .pdf (yay for paywalls keeping all of the non-ivory tower plebs out! huzzah!), but for those with access, the paper can be found at Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice. For those without access to an academic library, the first author provides an email contact. One presumes that a polite request would yield the full text of the paper.

Re:Climate "science" has never been consistent.

[Gadget_Guy]

Care to specify which sentences, or are you going to just continue to vaguely decry it as lies without actually addressing anything head on?

Ah, but that would be feeding the trolls. But if you look at the one bit of evidence that was provided (the link to Wikipedia article on global cooling), you find that this is the second sentence:

This hypothesis had little support in the scientific community, but gained temporary popular attention due to a combination of a slight downward trend of temperatures from the 1940s to the early 1970s and press reports that did not accurately reflect the full scope of the scientific climate literature, which showed a larger and faster-growing body of literature projecting future warming due to greenhouse gas emissions.

This directly contradicts the timeline presented that the science lacked consistency. The other massive claim is that there has been no real action to cut down on emissions. This ignores that we are moving to energy efficient products (even to the extent of banning the non-efficient versions). It ignores the construction of renewable and low emission power plants and the phasing out of old, dirty plants. It is such a stupid claim, and an obvious troll.

The rest is just the usual denier bullshit that has been addressed time and time again.

Science versus politics

[Okian Warrior]

I think you mean arguing against facts, because that's all that xkcd comic was. Which sounds exactly like something an anonymous coward would do.

As much as people like to insult and deride the other side, there are valid concerns there. The concerns are so large and looming that the "correct" side has lost a lot of credibility. I think a lot of the public is noticing the elephant in the room, and this is giving the deniers leverage in the minds of the people.

Rather than continue to insult and deride, perhaps it's time to address the credibility gaps.

Point 1: Scott Adams pointed out that when asked the question "how much of global warming is caused by humans, and how much is natural" in debates and televised interviews, no scientist had an answer. Specifically, Bill Nye, who is the global warming champion, didn't have an answer to that question.

Point 2: Another Scott Adams observation is about the models. Why is there more than 1 model? Shouldn't scientists agree on the best model and just use it? Shouldn't scientists agree on the best *data* and just use it?

Point 3: Also from Scott Adams is the observation that NO other complex model has ever had predictive value, and why should we believe that this one does?

Point4: From my view, climate change is closely tied with the actions that "we must do to save ourselves!", and those actions are always a) part of the liberal agenda, b) involve reducing our standard of living, and c) negatively impact most people while further lining the pockets of the rich and powerful.

Nowhere do we see proposals that make more electricity available to more people, nowhere does anyone point out that 85% of all resources are used by industry (therefore reducing home electricity consumption is less effective), no one proposes solutions for a decentralized grid, or reducing consumption by giving everyone fast internet access (doing things online generally uses much fewer resources than in person), or changing tax rules to promote telecommuting, or any of a hundred other easy changes that would make our lives better while being more efficient. It's always about enduring more hardship.

Point5: From my view, the "correct side" has lost a lot of credibility simply by their actions over the last 3 months.

If "that side" will riot over the outcome of a fair election, headline unsubstantiated lies, leak secret information for political assassination, call for literal assassination, how is it that they have any credibility over other issues?

Leonardo DiCaprio flies an eyebrow artist 7,000 miles to do his eyebrows, and we're supposed to believe him about global warming?

It's not that I don't believe in the science behind global warming, I do.

I just don't believe in the politics of global warming, that's all.

Re:Science versus politics

[Immerman]

If all you've heard is "we need to lower everyone's quality of life", then I suspect you've been listening primarily to sources contributing to the smear campaign, because I've heard a great deal of things along the lines of "let's promote transitioning to other energy sources" and "Let's move government subsidies from fossil fuels to emerging alternatives".

The science of anthropogenic global warming itself is actually quite simple - adding more insulation slows heat loss, and the planet has to get hotter until it resumes radiating heat as fast as it's getting it from the sun.

Crude back of the napkin calculations ignoring all subtleties and knock-on effects (the vast majority of which will make things worse): water vapor and CO2 combined are responsible for the vast majority of the greenhouse effect. There's about 10x as much water vapor in the atmosphere as CO2, so assuming both molecules are similarly potent infrared scatterers, CO2 is responsible for about 10% of the total planetary insulation. Human activity since the industrial revolution is clearly responsible for about 25% of the CO2 in the atmosphere, meaning we've increased total planetary insulation by about 2.5%. To restore the energy balance, the planet must therefore radiate about 2.5% more energy. Thermal radiation increases with the 4th power of temperature, so we can therefore expect planetary temperature to increase by a factor of (1.025)^(1/4) = 1.0062, or 0.62%. Current average temperature of the planet is 289K, so that translates to an increase of 1.8C, or 3.2*F, possibly not enough to be devastating on it's own, but quite sufficient to potentially allow normal variability to push things past a tipping point so that the planet transitions back to a tropical/desert state, probably killing most life in the process (a warm Earth is potentially more hospitable, but the transition periods have generally not been kind). And of course that's also only the expected change if we managed to completely halt the increase of CO2 today, which is all but impossible.

Where the model gets complicated is trying to make it predictive in the face of a chaotic system - there's *lots* of different forces in play, and to actually become meaningfully predictive you have to take into consideration at least the overwhelming majority (by effect weight). You don't need any of that to know that "doing X is going to be very bad", but you *do* need it if it's clear that "doing X" will continue despite your warnings, and you want to be able to predict what exactly "very bad" is likely to mean so that you can start preparing for it.

Basically, most of the climate science for the last few decades or so has had little to do with proving human responsibility - that was already done many decades ago and the observations are continuing to support those crude predictions relatively well. Current research is trying to make the model usefully predictive so that we can pinpoint where exactly the tipping point is (have we passed it already? Is there realistic hope for avoiding it?), as well as giving us as much warning as possible as to what we need to prepare for.

For example, over a decade ago I attended a talk by a group who had run by far the most detailed simulation of expected climate change effects in California over the next few decades - which predicted that within ~30 (50? I forget) years California would no longer have any substantial snow pack, meaning their water would come almost entirely as floods. Their recommendation was to start building dams immediately since due to the engineering and political challenges, dams have an expected 20+ year lag between when the decision to build them is made, and when they're actually completed. Got to start the process today if you want to have them finished in time to be useful. Thus far, their predictions seem to be holding up fairly well.

As for DiCaprio's hygiene choices - so he's a hypocrite, so what? So am I for that matter, though I don't have the resources to be nearly so excessive

Re:Science versus politics

[pointybits]

Point 1: Scott Adams pointed out that when asked the question "how much of global warming is caused by humans, and how much is natural" in debates and televised interviews, no scientist had an answer.

Getting your climate science from people yelling at each other on TV (or Scott Adams for that matter) is a bad idea.

From IPCC AR5, back in 2013: It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together. The best estimate of the human-induced contribution to warming is similar to the observed warming over this period.

Re:Science versus politics

[pointybits]

Point 1: Scott Adams pointed out that when asked the question "how much of global warming is caused by humans, and how much is natural" in debates and televised interviews, no scientist had an answer.

The answer is 50-70% according to this latest research.

Don't confuse the effects on Arctic ice with global warming. This research is saying that 50-70% of the ice melt is caused by the temperature increase from global warming. Our current best estimate is that 100% of global warming is caused by human activity.

Re:Science versus politics

[religionofpeas]

Why has natural variation in temperatures ceased just because we are on the scene?

You are quite correct, it hasn't. Natural variation accounts for -10%, and human contribution is actually 110%.

Re:Science versus politics

[tbannist]

Gosh, that is quite hilarious. Presumably you have heard of Ice Ages large and small and the Holocene optimum. Why has natural variation in temperatures ceased just because we are on the scene?

Because you apparently don't know this: the long term natural trend is towards lower temperatures. Looking at the historical record, we see a significant upwards spike at the end of each glacial period followed by a slow decline (10-20 thousands years) into the next glacial period. Our post-glacial spike period ended thousands of years ago and the earth has been in a slow slide into the next glacial period since then. While there is some natural variability, over relatively short time scales (20 years) that variability tends to negate itself, and the longer term variability is actually currently net negative, meaning it's cooling the earth and slowing down climate change.

So when the natural factors are a net negative trend then human activity, by elimination, is responsible for 100% of the net positive trend. That's not even science, it's just math.