There was an extremely fine interview on KVMR's science show Soundings today with UCAR's Robert Henson, author of the Rough Guide to Climate Change; it's available as a podcast.
Note: Host Al Stahler found this report incomplete and unbalanced, so if you listen to the podcast, please be alert for points Henson made that I missed or misrepresented below - corrections and additions will be gratefully received.
(In retrospect, the disconnect is obvious - what I viewed as an interview, Al viewed as a conversation.)
Jan. 18 update: Al has responded with one such point - see below for details
From my (fallible) notes, Henson's points:
- Climate change will probably be the biggest environmental issue in our lifetimes;
- The CO2 we dump into the air is easy to overlook since we can't see or smell it, but it's a huge amount; imagine if it was like horse manure...
- About half of what we emit stays in the air, and the amount in the air increases every year (even though we're adding less with the economy down, we're still adding); the amount absorbed on land, e.g. by trees, is about 25%, but varies enormously - & with fires, the land can actually be a net *emitter*(source) of CO2;
- Past climate changes due to natural cycles show that the climate can change, and their temperatures have closely tracked CO2;
- Relative contribution to current warming of humans vs natural factors? [this Q wasn't answered directly; see bottom of this post for followup]
- There are lots of things in science that we'll never know exactly, but that doesn't mean we have no idea.
- [Fractional risk attribution study (link)] results from Stott et al looking at the European heatwave indicated that climate change had boosted the chance of such an event 3-fold; it's a matter of probabilities, like an underdog football team - you might expect the underdog to win a game or two, but not the championship.
- There are two separate issues, 1) what will happen if the climate warms up and 2) what we should do about it; too often, people conflate them, and allow their views on #2 to determine their views on #1; which is faulty since science should inform policy, not the other way around.
- With regard to policy, yes there are some iffy actions pushed by political interests, but we should certainly look at the most sensible steps & focus on those, there's so much low-hanging fruit;
- What we should expect - precipitation *is* changing, and in accordance with predictions; be prepared for extremes, expect - as we're seeing - intensification of both rains and drought - more intense flooding due to more water vapor , and more intense drought due to more evaporation.
- There's been intense loss of sea ice; Hudson Bay has 25% open water, when typically it freezes around Thankgiving, this is virtually unheard of;
- Arctic sea ice still hasn't recovered from sharp drop in 2007
- Extreme Arctic warmth - e.g. Canadian weather station reporting low temperatures that are 60 degrees (F) above the average low;
- Yet cold, snowy U.S. winters; should we expect more of these as Arctic ice melts? too early to tell;
- Jeff Masters analogy - "warm Arctic plus cold U.S./Europe/Russia" is like a fridge with the door left open; kitchen's cold, but fridge contents get warm
- ...but all we hear about's the cold, since so few live up in Arctic where it's toasty
- We'll have surprises in future; weather's variability plus added warming climate. It'll rain or snow harder, droughts more intense, heat waves more intense, expect heat wave mortality in cities not prepared for it.
- re glaciers, a study from last week (link?) suggested that (many?) small glaciers are likely to disappear w/in this century.
- Clouds are indeed a wild card, varying in effect whether they're high clouds(warming) or low (cooling); but there's strong reason to believe there'll be a net warming even in the best case;
- And "Uncertainty...is not a source of comfort", since it cuts both ways, things could just as easily go worse than expected;
- Why are so many weathermen skeptical about climate change? partly it's "seeing the forest(climate) vs the trees (weather)"; partly it's because weatherfolk aren't trained in climate dynamics; partly a culture clash, working weathercasters have bachelors degrees & climate scientists have PhDs - populist vs. elitist. Asking weathercasters about climate is like asking dermatologists about lung cancer, it's not their specialty.
- Tornados don't seem - so far at least - to increase with climate change, the # of severe ones has stayed constant; the connection between hurricanes & climate change isn't straightforward.
- What to do about policy? so much low hanging fruit (energy efficiency) ,e.g. car mileage; U.S. is behind in efficiency, lots of easy things we can do to catch up;
- Henson is Conservative on energy - fossil fuels are a gift; we should conserve them, not burn them all now.
- Alternatives have to be used, we've got to push in this direction.
- Though ultimately, we can't consume our way out of the problem; there will be conflicts with capitalism, consumption, and population growth. More consumption is not inherently better.
Some areas that weren't addressed during this interview - unavoidably, since it was under an hour - include:
- Ocean acidification
- The "adaptation/mitigation/suffering" triad - we will have some mix of the three, and by our actions, can influence what mix we get.
- The time effect - like investing for retirement, acting earlier makes more impact than acting later.
- Deniers vs. skeptics, and how to tell the difference
- The "bathtub" metaphors - where the tub's water level represents either atmospheric CO2, or earth's temperature. The "water level represents CO2" tub metaphor helps make clear that reducing our CO2 emissions won't reduce existing atmospheric CO2 until the drain is taking away more than the faucet puts in (or, for an alternative metaphor, "slowing emissions of carbon dioxide is somewhat like slowing credit-card spending" (*)). And the "water level represents temperature" metaphor, where the tub contains an active child, shows the [heat] sloshing around on top of the (increasing) average. ) And for economists, there's a bathtub-and-Tetris corollary.
- Longevity of atmospheric CO2 - much of the CO2 humans emit will continue to influence earth's climate for centuries (link). So what we do now, we do to, or for, our children and grandchildren, and for generations beyond.
- [Added Jan 13] As I recall, no mention of potential massive climate change effects on Sierra snowpack (& thereby Calif agriculture), & on wildfires; both of which are ominous. Also (again from memory) when Al brought up "Shasta's glaciers are increasing", did Henson mention that this is likely to be transitory? (warmer winter weather does increase snowfall *up to a point*, but further warming decreases it. And I'm a little beyond my expertise here, so take with some salt.)
Followup #1: Al had asked Henson how much of current warming is due to humans vs natural factors, but as I recall, Henson didn't give a direct answer. So I emailed him asking it again, & saying that I understood the answer to be "somewhere between 80 to 120% of the observed warming" (from climatologist Gavin Schmidt) - i.e., that while earth's internal variability may have had some influence - as likely downward as upward - on earth's temp in the last few decades, we know of no natural drivers that are currently acting to nudge earth's temp. upward.
(i.e., the orbital changes etc. that create natural global climate cycles aren't currently changing, at the rate that'd cause the (geologically) rapid temp. increase we're seeing.)
(Henson responded inconclusively - saying he didn't feel prepared to assign percentages (or ranges thereof) to human-vs.-natural, but agreed that we see no known natural climate change drivers at work. I then asked here (link) at RealClimate for references, & got several helpful replies (image, testimony pdf).)
On this "attribution" question, one apparent area of confusion is what other conclusions can be drawn, from the IPCC statement that the science indicates "Most of the observed recent warming is very likely (i.e., 90% probability) due to human influence"; some take this to mean that therefore "some of the observed recent global warming is no doubt natural".
Future IPCC statements would do well to clarify that this doesn't logically follow.
Followup #2, Jan. 18: I'd requested corrections & enhancements to this account (of Bob Henson's remarks), and Al has responded, saying:
"You heard Bob agree that climate scientists don't know yet whether the day- after-day of sunshine, the change in currents & change in winds that melted the Arctic Ocean ice in 2007 could be blamed on climate change, or had some other cause(s) - perhaps your readers would enjoy learning about this."I went back & listened to the recording, & my impression is that while Henson agreed we don't know why 2007's Arctic ice loss was particularly massive, he also didn't consider it among the more important points to convey.
At about 32 minutes in, Al made this "climate scientists don't know yet..." point; & Bob responded "that's the 64k question" - as a segue into talking about what the *consequences* of the Arctic ice loss might or might not be, for our winters - i.e., it was not clear that the "that" of "that's the 64k question" was with reference to Al's statement (since Henson didn't act as though it were the 64k question, moving on immediately), or to the more important points he was about to make, about how we still don't know whether a more ice-free Arctic will tend to cause frigid U.S. & European winters like the two consecutive ones we've had.
(Keep in mind the big picture, that 2007's ice loss was an anomaly in severity only: the Arctic has been losing sea ice for decades, in accordance with predictions from climate change.)
Another difference & clarification - in the introduction to the interview, listeners were told that while atmospheric CO2 goes up in general, it does not increase every year - something Henson did not appear to agree about. As you might be able to tell from this graph (of atmospheric CO2 at Mauna Loa, showing CO2 increasing year by year, zigging in the Northern Hemisphere summer and zagging in NH winter), this statement is literally true, although not helpful for conveying the big picture: in the year 1965, 45 years ago (when our CO2 emissions were lower), some of the measurements were lower than in the previous year.