It is irrational to extrapolate the next 50 years of sink based on the previous 50 years. The distance from historic specific flora range and range made more robust by enhanced CO2 increases yearly, as flora can’t spread as fast as its potential range will allow – particularly around different obstacles like basins and ranges.

But, that’s all pretty much irrelevent to the question at hand as apparently few here save our host:
http://tinyurl.com/on9n8
understand that Dubya can’t do a *thing* about the future emissions of China and India et al.

Call me a cynic, but I doubt this administration’s ability to put together a realistic plan for anything.

Thanks very much for commenting. (Though I think that this comment was intended for another thread.)

You write, “We labored hard to ensure that nothing in the brief carried political tone or intent. This brief is about risk, of what we know and what we don’t know, in relation to anthropogenic climate change.”

The submisison of an amicus curiae brief is fundamnentally a political act. There is nothing wrong with politics, it is how we get done the business of society.

Science becomes pathologically politicized when political acts are (mis)characterized as scientific. Judgments of value, which you have clearly and in my opinion convincingly made, are not something to pretend do not exist.

I do not have a problem with scientists serving as advocates. The problem is serving as an advocate but hiding behind science.

Thanks!

You write, “All this discussion is academic.”

No, if technologies (such as solar cells and fusion) are truly capable of generating emission levels near 1-2 GtC before the end of this century, it would almost certainly limit the temperature rise in this century to approximately equal to or below 1 degree Celsius. (Unless the sun gets a lot stronger, which seems unlikely.)

“Injecting some reality that precludes any quantitative analysis here, we don’t know how much flora is going to spread (nor at what rate) due to increased CO2. All we know is that it will, correct? I don’t believe that is even considered by anyone here, also correct? That will increase natural sink by some unknown amount, so that 450 ppm may indeed be possible by mid century…”

Actually, we *do* have a very good idea how the natural sink is likely to behave in the next 50 years. We can simply look at how it’s behaved in the last ~50 years.

The airborne fraction of CO2 has averaged almost dead on 58% for the last ~55 years. So the natural sink has averaged almost dead on 42% of emissions for the last ~55 years. See slide #4 of James Hansen’s Keeling Lecture:

http://www.columbia.edu/~jeh1/keeling_talk_and_slides.pdf

So it seems very likely that natural sinks will average about 40-50 percent of emissions for the next 50 years.

It’s unlikely that the atmospheric CO2 concentration will be below 450 ppm in the year 2050. (I estimate the probability somewhere between 5 and 50 percent.)

http://markbahner.typepad.com/random_thoughts/2006/04/complete_set_of.html

Mark

I suggest that interested readers should consider reading the Amici Curiae brief and determine for themselves if the discussion is about scientific knowledge and associated uncertainty, or whether it is a “disingenuous” “political” piece as Roger Pielke writes. Perhaps Prof. Pielke might carefully reread the brief. We labored hard to ensure that nothing in the brief carried political tone or intent. This brief is about risk, of what we know and what we don’t know, in relation to anthropogenic climate change.

The relevant section of the Clean Air Act is about risk too, that’s why Congress inserted the language “may be reasonably anticipated to endanger” as the trigger for regulation. It is a scientific judgement, not a political statement, as to whether greenhouse gas emissions pose that kind of risk. It is not “insincere or calculating” (the definition of “disingenuous”) for scientists to address this question–if not scientists, then who should do it?

The reader might be surprised that the brief connects CO2 reuglation most directly to the decision to remove lead additives from gasoline. At the time the ban was set into motion in the 1970’s, there was good scientific evidence of harm from lead emissions, but the impact was far from certain or precise. One could argue many different ways as to costs and benefits of leaded gasoline.

Only now, 30 years later when blood lead levels in the US have dropped by factor ~6, can the damages to health be clearly assessed. The net benefits of banning lead additives were many, many billions of dollars, plus better health and longevity for tens of millions of people. As noted in the article cited in the brief, the damage to health was far worse than thought at the time of the ban.

Climate change affects the whole globe and cannot be reversed in a decade like airborne lead pollution, in fact, reversal is essentially impossible. Does the reader think the risks of unrestrained emissions of greenhouse gases are bigger, or smaller, than for lead emissions?

Thanks for your comments. We welcome your input. I’ve got no problem with people arguing with me, criticizing my posts for their logic or even their tone. That is why we put ideas and arguments forward — to stimulate discussion and to learn from each other. All of this is fair game. Where it become counter-productive is when people begin focusing on trivialities (e.g., definition of “feature” anyone?;-) or start slinging insults, which I am sensitive to becuase in the past on this site they have gotten quite out of hand, and I won’t let that happen again.

If you honestly believe that I’ve treated Mr. Hamilton unfairly, then say so and explain why. Hijacking the post to prove a point is not productive in my view. In the end it is fine for particfipants here to agree to disagree and leave it at that!

From my perspective, Hamilton’s comments sill make no sense. And neither did your comment early in the post. When it was clarified that I, and the article I cited, were discussing carbon dioxide only and not a basket of gases, perhaps that cleared up the confusion in your comments about exceeding 450 for a few decades. This still doesn’t get Hamilton off the hook. Maybe he was misquoted. Maybe he thought the article was going to be about a basket of gases. Who knows? I still find the seeming reflexive opposition to policies not yet announced quite telling. I would think that if any president announced a commitment to 450 ppm at any timescale the environmental community would be dancing in the streets . . .

Thanks.

There are two reasons that I often post about what I see as contradictions between your expressed beliefs and your exhibited reasoning. The first is that many of your post are of precisely this “gotcha” nature (tahis includes the current post and one that even used my own statements), and frankly what’s good for the goose is good for the gander. The second is that you hold other people to a much higher standard than you hold yourself. This thread being a compelling example.

You have seized on an isolated comment of David Hamilton’s about a hypothetical and ambiguous policy goal and tried to claim it shows something very base about his motives. I think that is pretty much the essence of a “gotcha”. When you are shown very clearly that there is nothing wrong with what he has said given one very reasonable assumption about what the unknown policy involves, you do not uphold the standard that you demand of others.

You may have more evidence that David Hamilton is simply anti-Bush no matter what Bush’s policies are, but you have definately not made your case here.

Best Wishes.

One tongue in cheek (maybe) comment though – this discussion is about the U.S. setting some arbitrary limit to atmospheric concentration. I guess that you are all assuming that the goal of Dubya is to take over the world, and that he will succeed…

You write, “As I said to Coby, we probably have far more relevant issues to discuss than 1GtC levels of annual emissions this century.”

Well…if you think that 1GtC of emissions this century is totally out of the realm of possibility, you probably should spend quite a lot more time studying energy technology and technological trends.

Let me give you an example. Currently, all energy sources (coal, oil, natural gas, nuclear, hydro, etc.) represent about 8% of the world economy. That’s from my memory of this seminar:

http://carolinafirst.unc.edu/ath/page18/page18.html

So…the current world economy is what…$60 trillion? (Again, from memory.)

So ALL energy is a $4.8 trillion business (again, that’s oil, coal, natural gas, nuclear, etc.).

Currently, photovoltaics is a $10 billion business, and growing at 40 percent per year. (From the announcement for the photovoltaics seminar I’m attending this afternoon. )

So that’s $10B/$4.8T = 0.2% of world energy spending. That’s trivial.

Let’s say that trend in photovoltaics growth continues indefinitely into the future. What sort of numbers would be produced?

2010 = $27 B (trivial)

2015 = $150 B (still trivial)

2020 = $790 B (starting to be important)

2025 = $4.3 T (a monster!)

2030 = $23 T (essentially ALL energy in the world)

Now, this is an extremely crude assessment. But there is no *fundamental* reason (e.g. lack of sunlight, environmental or other public opposition) why photovoltaics could not supply ALL the world’s energy. And that *could* happen by midcentury, and *could easily* happen in the second half of the century.

Now, back to real work,
Mark

Thank you much for reengaging on the substance. A few replies.

1. Lets get one thing out of the way up front. You say of my assertion, “This isn’t true.” We are not discussing truth or falsity here. My views on the ability of the world to reduce emissions below the natural sink is an _opinion_, as is everyone else’s perpective on emissions over 100 years. Let’s dispel of talking about the “truth” of such views. I find it implausible to think that annual CO2 emissions can be reduced below the level of the natural sink in the next 50-100 years, you disagree. Good. Time will tell. But for now we can certainly accept that we hold different opinions on this subject.

2. Going back to the first post on this thread, it makes little sense to try to divine the details of a plan that may or may not exist and for which we have no details. I’d much prefer to discuss something concrete, like Pacala and Socolow, as I did in an earlier post this week.

3. As far as the stabilization path mattering, I would agree that it does if we include methane and nitrous oxide, as well as other GHGs, as oppenheimer’s work argues and as discusssed in the DEFRA report. But discussing _CO2 only_ (which I have been doing all week), I do not believe that the exact path matters much if at all, as WRE 1996 argues. If you have a CO2-only citation that makes a different case on the importance of the stabilization path, please share it and I will read with interest. My current understanding of the science is that absent annual emissions dropping below the natural sink (which I completely discount, as I’ve said) or air capture (as I’ve argued), the effects of emissions reductions on stabilization will be minimal in any case.

Bottom line … debating the effects of reducing the final 2.5 GtC in annual emissions may be a fun theoretical exercise, but until there is evidence/reason to believe that the first GtC is going to be reduced, lets be clear that we are talking about angels on a pin.

Thanks.