Flirting with Disaster: Greenhouse Gas Report

We need to reduce greenhouse gases in the atmosphere, and we need to do it quickly. The main ones increased by humans are carbon dioxide (CO2), methane (CH4, the main component of natural gas), and nitrous oxide (N2O).

How are we doing?


Let’s start with CO2. Here’s the atmospheric concentration (in ppm, or “part-per-million”) according the the atmospheric observatory at Mauna Loa:

The black line shows the concentration, and reveals a regular up-and-down pattern each year; a seasonal cycle of CO2 at Mauna Loa. The red line show what we get when the seasonal cycle is removed.

Of course we’re most interested in what has happened lately. Here’s the data since the year 2000:

The black line shows the CO2 with the seasonal cycle removed. The red line is a straight-line fit (by least squares regression), which rises at a rate of 2.15 ppm/year. But the data don’t follow that straight line perfectly, especially recently. Here are the residuals, what’s left over if we subtract the straight-line values from the oberved values:

There was a sharp increase of about 2 ppm on top of the already existing trend right around 2016. Part of that is temporary, due to the strong el Niño, but it hasn’t subsided so much of the increase remains.

Bottom line: we haven’t stopped CO2 growth, we haven’t even slowed it.


What about methane? Here’s the atmospheric concentration measured at Cape Grim in Tasmania, Australia:

Here’s what’s happened since 2000:

It had levelled off during the early 2000s, but started rising again about 2007. Lately, there’s no sign of stopping or even slowing.


What about nitrous oxide? Here’s the data from Cape Grim:

Since the year 2000:

Again, no sign that we’ve stopped increasing or even slowed down.


There is, as yet, no sign of any slowdown in the growth of greenhouse gases. That emphasizes how hard this is going to be. But it’s worth it to stave off destruction, destitution, injury and death. That’s what’s at stake.


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17 responses to “Flirting with Disaster: Greenhouse Gas Report

  1. we are talking the talk quite seriously.

    • I’m not sure about the graphic, Doc. Subliminally, it might be saying vote RED for climate. Isn’t red associated with Republicans? Of course, the line is a bit more nuanced than that, as Tamino has pointed out before but, in general, this would be the wrong message.

  2. Thomas Everth

    An interesting correlation of the CH4 uptick: It started with the beginning of the Fracking boom… Coincidence?

    • rhymeswithgoalie

      I thought so, too. Increasing permafrost melt might be another contributor.

      I also noticed the CO2 rate dip below linear ~2008, the start of the worldwide recession.

  3. Surely, the Keeling cirve demonstrates that atmospheric CO2 levels have been accelerating, and if emissions are a reasonable gauge of the atmospheric rise, that acceleration has been continuing through most of the period 2000-to-date. Emissions today are some 40% higher than they were in 2000, 50% if you look at FF emissions and ignore LUC.
    Is it then appropriate to put a straight line through the data?

  4. Jim Hansen’s latest missive (PDF) suggests that a way to look at the warming rate is to look at the rate implied by joining the current La Niña (which has just bottomed out) to, separately, previous La Niña minimums. That method appears to show the most recent rate is double the long term rate.

    This seems too simplistic to me. Is it a reasonable way of doing it? Hansen says it’s better than El Niño maxima, since they are more variable.

  5. “This seems too simplistic to me. Is it a reasonable way of doing it? ”
    No, determining a trend by picking two endpoints is silly regardless of who does it. It’s kind of disappointing to see this from Hansen.

    Tamino’s “The Global Warming Signal” post from a week ago is a far more sensible analysis of the warming rate and changes in the warming rate over time.

  6. Hi Mike Roberts,

    If Hansen’s graph shows that warming has doubled since 1995, then I suppose we should expect something just shy of 0.4C/decade in the coming decades?

    I’d be willing to bet against that.

    Here are two linear trend segments starting and ending at two different La Nina periods of similar magnitude:

    http://woodfortrees.org/plot/best/mean:12/plot/best/from:1995/trend/plot/best/from:1988/to:2008/trend/plot/best/from:1973/to:1989/trend

    The segments are:

    1973 to 2011 slope= 0.185986 per decade
    1984 to present slope = 0.206798 per decade

    Each segment is > 30 years so I suppose they should largely show climate rather than weather. The two segments cover 45 years in total. It looks like there is an acceleration, but nowhere near double.

    Anyone want to bet that the coming decades will warm at twice the rate of the previous?

    Lerpo

    • Anyone want to bet that the coming decades will warm at twice the rate of the previous?

      No, because the more I were correct, the less likely I’d be to collect, due to the failure of societal resources or perhaps your personal ones, should climate change affect your finances adversely.

      On the other hand, when Hansen writes “We expect global temperature rise in the next few months to confirm our analysis,” I wouldn’t bet against that, either.

      No, determining a trend by picking two endpoints is silly regardless of who does it. It’s kind of disappointing to see this from Hansen

      Well, I don’t believe it was meant as anything more than illustrative. And to be fair, at least he’s picking endpoints via a reasonable criterion which is apparently a priori to the ‘desired’–or at least anticipated–result. But at best, it’s fitting a curve based on just 4 data points.

    • Given the way things are going, I think there is a fair chance of a further doubling within a few decades but betting on it seems to be trivialising the issue. The long term trend that Hansen shows is for a 48 year period. As Doc Snow mentioned, I’m sure Hansen’s point fitting is to illustrate that the rate may well be rising significantly over the long term trend. If the current La NIna minimum trend is 0.38C per decade, then 0.4C per decade in the coming decades would be a near certainty.

      Of course, if we reached that rise (or even if we stayed at 0.38C per decade) then 1.5C is already an impossibility.

  7. 20 days to US midterns.

  8. Hi Doc Snow,

    You said: “No, because the more I were correct, the less likely I’d be to collect, due to the failure of societal resources or perhaps your personal ones, should climate change affect your finances adversely.”

    We could pay up-front and have the money invested in a sensible (interest-bearing) place and controlled by a trusted third party who would eventually also judge the bets.

    But before you pony up too much money, consider what conclusions Hansen would have drawn in 2012 using the same methods. If you draw lines from the troughs of historic La Ninas to the 2011 La Nina you would (incorrectly) conclude that global warming was coming to an end: https://i1.rgstatic.net/profile/John_Fasullo/publication/259533764/figure/fig12/AS:272669211885582@1442020814729/The-five-ensemble-members-of-the-ORAS-4-ocean-reanalysis-OHC-for-0-700m-and-full-depth_W640.jpg

    Lerpo

    • I was mostly kidding! I don’t remember when I last made a bet in earnest, though I’m pretty sure it would have been with my wife, and for stakes amounting to small change.

      And I agree with you and Mark B that this is clearly not a robust method for detecting trends. As I said above, nothing “more than illustrative.”