Posted by: Barry Bickmore | November 1, 2011

Climate Change: What We Know and How We Know It

I did an informal presentation for the LDS Earth Stewardship group, which is now on YouTube.  If you can’t stand watching me talk, believe me–I understand.


  1. I have been thinking that one way that I might be of service to the Climate change issue in my own area is to do the leg work to get someone such as yourself to come to Grantsville and do a similar presentation in our community. Would you be willing to do that or do you know anyone of similar credentials as yourself that would?

    • Well, this presentation (I’m about halfway through as I write this and I think it is really good) allows Barry to scale.

      Consider maybe showing this very presentation (popcorn and large screen) and then if we coordinate many of these at the same time in many cities, we might at the end have a small panel to answer questions or something along those lines.

    • Kirt, for general-interest community talks, you should consider asking Greg Craven (see youtube, or, whose presentations are shorter & more geared to the general public & not as pure-science-oriented. Barry’s talk is more for people who really want to understand the science, more than just understand what the relevant issues & tradeoffs & concerns are.
      (I’m basing this assessment on the first half hour of this talk (which is standard climate physics) – Barry’s now getting into climate sensitivity, “the holy grail”)

      This talk of Barry’s is basically a lecture building from first principles, not a Randy Olsen-style “arouse and fulfill” style talk, or a “here’s what you need to know to be an informed citizen” talk.

      That being said, I am finding it’s nice to see/hear the science all slotted into context; but for people I know who haven’t been exposed to much climate science, I suspect it’d be too much to absorb.

      • Another good audience for this would be people who have a physics background yet don’t think climate change is human-caused; especially since they’re often local influencers, & so the effect of this talk would likely reverbrate through their communities.

        p.s. thank you Barry! both for giving the talk to your group, and for making it available online for the rest of us.

  2. Some notes & times from the talk –

    1-30 climate physics
    30+ sensitivity – models and paleo
    40 local v global temp
    44 is it happening
    47 Muller study
    48 no q that it’s happening, & how much it’s happened;
    If it stopped here, nobody would care that much;
    but if we do understand why the temp is rising, if we keep emitting GHGs it’ll keep rising

    50 is it us?
    52 temp started going up before the Industrial revolution, been increasing for 3-400 years; (over that period) there are natural factors going on
    Addressing “is it the sun” Q?

    57 volcanos? us 130x co2
    58 isotopes show co2 increase is us (isotope % graph goes down, so confuses)
    59 climate models – keep track of known natural forcings; temps match the projected temp change that includes human influence, not the “natural only” one
    1:01 SkepSci graphic “how we know we’re causing” – multiple lines of evidence
    1:02 should we care? it’s happened in the past, so what’s the problem?
    maybe we should just ride it out, in our SUVs
    IPCC models show uncertainty, but most of the uncertainty isn’t about models, it’s about what humans will do
    Above 2 degrees (C) it just gets worse & worse & worse – & right now we’re pegged at the high end of that

    1:05 our daily swings are so big, so why to care if avg temp goes up?
    At last glacial maximum (lowest temp; ice sheets over much of earth) temp was 4-7 (C)degrees colder
    400mya, a giant swamp world – 6degC warmer
    500mya we had 7k ppm CO2
    1:07 earth has experienced changes over time, but they’re tied to mass extinctions
    PETM 58mya?
    yes lifeforms can adapt, but can adapt better if the changes are slower
    1:10 risks for various temp changes – over at higher temps, BB sees the 4 horsemen – and statistically, it’s harder to rule out the higher end
    1:12 Back at the PETM – nobody knows why the huge spike there – under certain conditions the carbon cycle breaks down, at least for a while – can get some rapid changes, & rapid is bad
    1:13 addressing the “we can’t afford action anyway” objection
    freemarket think tanks econ analyses…
    argue that windpower cost/kwh more than coal
    1:15 yet cost of externalities of burning coal
    1:16 graph showing econ analyses – true cost of burning coal (including the externalities) is about the same as other energy sources, even not including effects of climate change. Then if you add them in…

    Questions. (some notes here are from audience comments) –
    1:18 “but china” are ahead of us in solar – but also building boatloads of coal plants
    1:19 historically we’ve emitted way more than them
    1:20 how we cut a deal with them if we don’t bring anything to the table?
    And we can do this (reduction agreements) incrementally.
    American Physical Society estimates cost/yr is 2-3%; seems reasonable as an insurance policy against the end of civilization
    (prospects of conflict)
    Cropland in many countries is w/in a few meters of sea level

  3. Some thoughts on the talk:

    Could you maybe provide links to where your graphics are available, online? I haven’t seen some of them (especially the “risks for various temp increases” one), & others I’ve seen but have trouble finding.

    It’d be good to revisit the difference between scientific and common usage of words:
    (I’d also include “significant”/ “substantial”, & for positive & negative feedback, escalating and damping)

    The “bathtub” metaphor here was used for atmospheric heat, not for atmospheric GHG concentration; (unless I missed the latter) which might confuse some.

    CO2 Isotope graph dropping down, to indicate increasing fossil-fuel-origin atmospheric CO2, requires audience brains to do extra work, & they’re working hard as it is.

    • And one more suggestion: Toastmasters. Not only do they give *great* feedback, but it’s also a wide community cross-section, to reach.

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