So tell us Andrew, what percentage of the global warming of the last 25 years is anthropogenic? And what percentage is natural?

Then tell us why the fact that 47% believe there is solid evidence that humans are responsible is unacceptable. What should this number be, exactly?

Please give your answer here.

I suspect that if everyone actually looked at the evidence (as described in the IPCC report), the number would be much higher.  Obviously, some people are "closed books" and no amount of data will convince them, so it will never be 100%.  I suspect it might be 70-80%.

For anyone else, the short answer is that the present warming (about .6C since the beginning of substantial industrial emissions around 1850) is thought to be from a combination of natural factors (mainly volcanos and solar variations) and greenhouse gases.  The primary concern is with regard to future warming, which at this point is likely to be not less than about 2C, but possibly considerably more.  

For more information on this and other climate issues, the Pew Center is a good place to start.  For more detail on the science, Real Climate is the best source.  Finally, the new IPCC report I linked above should be read by anyone with an interest in the future of the planet.  There will be extensive discussion of the report, which is updated only once each six years, here and on Real Climate.  

Andrew, please provide a citation for this scientific conclusion.

> I suspect that if everyone actually
> looked at the evidence (as described
> in the IPCC report), the number
> would be much higher.  

Andrew, again, please provide a citation for this scientific conclusion. How much "higher?" Please be specific.

> Obviously, some people are "closed books"
> and no amount of data will convince them,
> so it will never be 100%.  I suspect
> it might be 70-80%.

Andrew, please provide specific citations in the scientific literature where these conclusions may be verified.

---

I'd like answers to all four of these questions, please.

If not, then please admit that you are talking completely out of your ass and you have no academic evidence whatsoever for numbers which you are making up as you go along, all for the sake of your "environmental" agenda. And then, for good measure, you can withdraw your assertions until you learn what true knowledge is composed of.

We are waiting.

I have merely asked for citations in the academic literature for Andrew's assertions. Is this such a sin?

Surely you believe that the conclusions expressed on this blog should be well-grounded in scientific study?

If not, let us know now, and we can easily and quickly dispense of you altogether.

Otherwise, I would like answers to my questions about Mr. Dressler's assertions. He has, so far, not given any, and I, for one, will not believe something merely because he asserts it.

If he cannot or will not provide such evidence, I shall be forced to conclude that Mr. Dressler exaggerates and imagines his data in order to back up his agenda. I'm sure, Mr. Bloom, that you will agree that such imagination is scant comparison to truly accurate and scientific data and conclusions. Yes?

You wrote:
> For anyone else, the short answer
> is that the present warming (about
> .6C since the beginning of substantial
> industrial emissions around 1850)
> is thought to be from a combination
> of natural factors (mainly volcanos
> and solar variations) and
> greenhouse gases.

Yes, yes, yes, we all know this. We have known it for at least five years, and some of us for more. But it does not answer my question, as I suspect you already know. The question is about this "combination." What percentage of this 0.6 C increase is anthropogenic, and what percentage is natural? Only after you or Mr. Dressler answers this question can we decide whether 47% is a legitimate number for the percentage of people who blame global warming on man.

I await your answer--with proper citations, of course.

I truly believe that it is much more complex than that.  First, Global Warming is an effect not a cause.  Global warming is what happens after you monitor years of data for CO2, methane and nitrous.  However, those three gases did not cause Global Warming by themselves, they are only reported as a few of the plausible candidates, since the computers  were very crude as to their inputs.

Aerosol is the wild card, and few people are even concerned about it - a notion I find very strange.  Aerosol is particulate matter, fine dust, smoke, and exhausts suspended in the air (even in outer space).  

• Elemental aerosol tends to reflect light and cool the atmosphere, not only by shading but by refraction as well (Global Dimming).

• Organic black carbon tends to absorb heat energy and warm the atmosphere (Global Warming).

It's some pretty complex stuff.

Onward through the fog

How do we know that recent CO2 increases are due to human activities?

Attribution of 20th Century climate change to CO2

You'll need to follow the various links for the details, and it may be helpful to use Google Scholar to check for any more recent research.  Have a lovely time!

My estimate that 70-80% people would agree if they understood the scientific evidence is my opinion based on years of following polls.  

There are lots of scientists who spend all of their time thinking about aerosols.  Over the past 5 years, our understanding of aerosols has increased dramatically.  In fact, we can now monitor them from space (with some caveats, of course), so we actually have a pretty good handle on their contribution.  While they are important, their dominant contribution is to cool the planet.  Well-mixed greenhouse gases, like CO2, are the dominant cause of the recent warming.

When the IPCC's 4th assessment report comes out in early Feb., you'll see how good our understanding of aerosols has become.

And you know this how?

Mark Bahner

   Unfortunately in much of America, the only voices heard are the corporate shills and the right wing media.  In most of the so-called "red" states, there is no real diversity of media opinion, no effective voices telling them that global warming is caused by human activity AT ALL (or contributed to).  So, they don't hear the science, and when they do, the science is carefully placed at an equal with "balancing"
opinions.

   Supposed you watched a show, and there was an expert on it saying that UFOs do not exist.  Immediately following, another "expert" explained that they do.  What would you believe?

   Remember the weapons of mass destruction?  Many people still believe in them, still believe in 9/11 Iraqi links.  A lot of the country is effectively under a media lock down tight enough that truth never penetrates.

   THAT is scary.

patrick

-Eric

> How do we know that recent CO2 increases
> are due to human activities?

> Attribution of 20th Century climate change
> to CO2

As I suspected -- you throw up a couple of extremely generic references and think your job is done. Hardly. These articles do not answer the question of what percentage of recent decadal warming is anthropogenic, and what is natural. That is the question we are discussing here, if you forgot. (I did not.)

> You'll need to follow the various
> links for the details, and it may be
> helpful to use Google Scholar to
> check for any more recent research.  

No. This kind of slippery talk won't wash here. You made specific assertions. That means, in a place where people care about the truth, that you will provide a specific scientific citation to back up your assertions, including chapter, page number, and quotations of specific sentences. Maybe you can throw off a couple of documents and convince the Greenpeace and Sierra Club people, but we have higher standards here. Much higher.

I await your response.

This hardly answers the questions I posed to your above. You made very specific assertions. I want to see very specific proof backing them up. That means you will provide chapter, verse, and page number.

You want to sound like a scholar? Then start acting like one.

> My estimate that 70-80% people would agree
> if they understood the scientific evidence
> is my opinion based on years of following
> polls.  

How did you come to this conclusion? What calculation did you do? Why is the number 70-80% and not 60-70% or 80-90%?

by Andrew Dessler

Let us also note that this is precisely what Grist is doing, although they're trying to raise fears, not doubts. They have a vested interest and they are spending money (by hosting this blog and paying people to blog on it). They are no different than any other interest group, and as this thread has made crystal clear, they will abuse science in order to present conclusions of dubious quality, for the sake of their agenda.

You asked for evidence that > 50% of the recent warming is caused by humans and I provided a link to a report detailing the evidence.  You clearly did not look at that link.

If you cannot take the time to read the table of contents and see that section E covers "The Identification of a Human Influence on Climate Change", then it's clear that you are a troll.  

I have, of course, dealt with people like you.  No matter what evidence I provide, it will not be sufficient.  I doubt we have much else to talk about.

Do you really think your demands warrant attention?

Who do you think you are?  Could you maybe consider that you're talking to humans who have better things to do than entertain trolls?  

If you want to debate, you have to at least show some respect for your opponents.  Otherwise, why should anyone respect you?

My apologies to all if this has been discussed elsewhere on Grist, but I'm compelled to ask d41295 a question.

d41295 wrote "... you have no academic evidence whatsoever for numbers which you are making up as you go along, all for the sake of your "environmental" agenda..."

Let us set aside the "disputed" numbers for a moment. You seem unwilling to look at them, so there is no point in discussing them with you. Instead, let's discuss agendas. You have chosen to attack the messenger and accuse them of pulling information out of their asses (to paraphrase you) in order to support their environmental agenda. Now it is easy to figure out how certain powerful corporations benefit from denying the reality of global warming. But how do scientists benefit from presenting false data?

More specifically, what sort of evidene do you have for the existence of an environmental agenda? A scientist who constantly presents false data will not get very far in an academic career. A scientist who presents false data will not benefit from the rising values of stock options. I cannot imagine how the Grist people benefit from pushing false data supporting global climate change. They are probably barely able to support their website, let alone make a living. They are smart folks who could earn much more money and ensure some financial security if they set aside morality and worked for one of the corporations denying global climate change. Please TELL us about the grand ENVIRONMENTALIST AGENDA. How do the scientists, environmentalists, Grist, and the people commenting here benefit financially?

Indeed, as a scientist involved in creating GMO plants, I should be thrilled by global climate change and eager to bring it on. I should be denying all evidence of global climate change and encouraging people to pump as much CO2 as they can into the atmosphere. It will secure my job for the rest of my life, as well as jobs of scientists who follow. The rapid and extreme fluctuations in climate that mark the transition will demand rapid and extreme measures to ensure an adequate food supply. GMOs will be important. So will research in agriculture. Moving beyond my own self interests, other scientific fields will require an influx of researches to create new technologies for coping with the changing climate. Moving beyond science, we will need a stronger and larger government to maintain an educated work force, repair infrastructure, and put new security measures in place as displaced refugees look for new homes.

Please... d41295... tell me about this enviromental agenda and exactly what the goal is. You apparently don't believe people are simply interested in saving the biosphere. Why would anyone make this stuff up?!

d41295's irritable poking should be ignored.  

Or how about this:  d41295, how about you provide Grist readers with some credible data that show that human activity definitely has not contributed to the recent increase in global temperature averages.

You do that, d, and then you can go back to your buddies and whine and complain about environentalists always "talking out of their asses."

Whatever, dude.  We all know that we don't know everything about climate change.  We never will know everything, even after it's just a chapter in some kid's history book.

But we do know, with absolute certainty, that things are definitely changing, like it or not.

This is an interesting topic because both the EU and US have major campaigns to reduce aerosol (PM-10 and PM-2.5 micron).  One might be able to make a case that as we reduce aerosol but do little about CO2, global warming would only accelerate.

I hope that made a little sense.  Thanks again for the message.  /sam wells

Onward through the fog

>Gar, you might want to take a look at the work of J.A. Krosnick et al., Public Understand. Sci. 9 (2000) 239-260. These general numbers (at least the 77%) haven't changed in 10 years.

On the reality of global warming you are right and I I have been citing those number for years. But the number who understand they are human caused is new. It used to be in the high 30's. 47% represents a real change in the U.S. It also means a majority of those who understand that it is real understand that it is primarily human caused.  Again, I predict that this is year in which we will see a majority of USAians understanding that global warming is human caused - which will puts us no more than a decade behind the rest of the world.

Me:  "And you know this how?"

"Because unfortunately we're going to pass 2x CO2 and not look back."

Two times the present ~380 ppm...so >760 ppm??  When do you think that's going to happen?

"I suspect something more like 3x will become inevitable by the time there are enough obvious impacts to motivate the sharp reductions needed."

3 x 380 ppm = 1140 ppm????!

Mark Bahner

If the reference is to pre-industrial CO2, are the temperature increases also with reference to pre-industrial temperatures?

Mark Bahner