This post is about myths of global warming, but calling it that would be dull; it was going to be called Fables of the deconstruction
seemed better and perhaps more obscure. Partly, its a feeble attempt to gain wordshare by recycling some old posts, but there is some new stuff. To save time and space I haven't trawled for the evidence of people that believe these myths.1. In the 70's, everyone was predicting an ice age
: fairly common in disrespectable circles but comprehensively refuted by the excellent if over-long and byzantine http://www.wmconnolley.org.uk/sci/iceage/
, and more comprehensibly by www.realclimate.org/index.php?p=94
. Yes I know I mentioned this only recently (and JF picked up on it
).2. Its all the Urban Heat Island
: no it isn't: see The Surface Temperature Record and the Urban Heat Island
. In fact, recent evidence suggests less
UHI that reported by the IPCC TAR.3. The surface may be warming but satellites show the atmosphere is cooling
: not true: depending on how you built the satellite record, it shows a warming of between 0.08 oC/decade and 0.26 oC/decade, from 1979 to 2004 (ish). See http://en.wikipedia.org/wiki/Satellite_temperature_measurements
for the details. There is a kernel of truth to the myth: once upon a time (last in 1996) the satellite record did show cooling, but never as large as the warming it now shows.4. The hockey stick is broken and therefore the current warming is not unusual
: the MBH98 "hockey stick" graph was groundbreaking in its day, but there are now several other reconstructions: the best pic I know of is at http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png
. But... its by no means clear at the moment which (if any is correct); and all show the current temperatures and rate of rise to be unusual. Its also true that the hockey stick is not quite as important as the septics often like to claim: What If … the “Hockey Stick” Were Wrong?
at RealClimate is interesting.5. The current CO2 rise is natural, not man-made
: this one is totally absurd. To believe this, you have to believe that CO2 and other GHG's were stable at pre-industrial concentrations for thousands of years
, then suddenly, just as humans started emitting them, some natural process started emitting them, while at the same time removing from the atmosphere an equivalent quantity of the man-made GHGs (yes I know about the resident fraction...). This is the obvious argument; more complex ones from isotopic measurements can be made, e.g. at How do we know that recent CO2 increases are due to human activities? (update)
. BTW, notice I've used "man-made": I could have said "anthropogenic" but this is just man-made said in greek.6. Climate is always changing
. True, but so what? We care about the magnitude and speed of current and likely future changes; "climate is always changing at current rates" is definitely false; its all about timescales. See Why do people say... Climate change 'is the norm'?7. Global warming will cause cooling! Or, the "Day after tomorrow" effect; or Thermohaline shutdown
: people love this one because it appears paradoxical. The basic idea (twisted so badly by TDAT (as I understand it; I never watched the stupid movie) that its unrecognisable) is that GW will, by freshening the waters of the north atlantic, lead to a shutdown of the thermohaline circulation, a shutdown of the gulf stream, and therefore massive cooling over northern Europe. THC shutdowns have probably occurred in the past, as a result of freshwater discharges, but only while there are large ice sheets over north america. The Gulf Stream is not the same thing as the THC. And as far as can be told, the probability of a THC shutdown is not high: in fact, it doesn't happen "by itself" in coupled models runs, you have to force it to happen; what you get is instead a slight slowdown
and although there is a cooling tendency from the slowdown, the overall effect is warming, even over northern europe. The TAR, section 126.96.36.199 Thermohaline circulation changes
is good, as always.8. The ozone hole and climate change
. Not really a myth, just a confusion: the connections between ozone hole (or, better, ozone depletion) and GW is thin. They are: (a) ozone holes require very cold conditions; GW will warm the troposphere but (possibly confusingly) cool the stratosphere where the ozone is; hence, there will be a tendency for GW to cause more depletion. OTOH CFC levels are expected to decline. (b) ozone depletion represents a radiative forcing of the climate system, overall a net negative forcing: ie, it tends to cool the troposphere and surface (c) both GW and OD tend to cool the stratosphere; this cooling is observed but not as useful as it might be as a fingerprint of GW, because of the ozone changes.9. The greenhouse effect keeps greenhouses warm
: not so
.10. Nils-Axel Mörner has something useful to say about sea level rise
: fortunately, very few people believe this one... perhaps this
is why...11. Uncertainty
. Once the septics have run through about every other excuse they are down to pressing the virtues of uncertainty: that because we don't know in enough detail the effects and size of GW, we should do nothing yet. Of course they don't really mean "do nothing"; they mean "do nothing to reduce our emissions of GHG's". This seems to be the current position of the Bush govt
: obliged to admit the reality of the current temperature rises, and even describing it as "sharply rising" (thus stomping on the std.septics, but they keep quiet about that), the POTUS continues... We do not know how much our climate could, or will change in the future. We do not know how fast change will occur, or even how some of our actions could impact it.
. Well, this isn't really right: we do in fact know that emitting CO2 will warm the climate. But anyway, (as Michael Tobis has argued on sci.env better than I can, sadly I can't find it right now) uncertainty should make you feel unsafe, not be some sort of we-don't-know-its-ok cocoon.
Well, thats enough myths for now. If I've forgotten some, I hope you'll let me know.