Folks obsessed with language exploded in mockery when US officials coined a new phrase, “man-caused disasters”, to serve as an overarching paradigm for understanding everything from climate change (sorry, “climate disruption”) to 9/11.
What most people don’t appreciate is that there is, in fact, a link between climate change and the Islamist attacks of ten years ago.
No, I’m not kidding. As most of you probably recall, one of the most disruptive effects of the jihadist attacks was the immediate grounding of all air traffic in the United States. This went on for three days, resulting - in addition to millions of frustrated (and terrified) air travellers - in something which hadn’t happened since the dawn of the jet age: a complete absence of aircraft contrails over the continental United States.
According to the US National Air Traffic Controllers’ Association, there are roughly 5,000 aircraft in the skies over the US at any one time, and 70,000 flights carrying two million passengers originate or terminate in the US each day.(Note A) In September 2002 alone, the US consumed 48,262,000 barrels, or about 2.4 billion gallons, of aviation kerosene (Note B). That’s a lot of air traffic.
(For the record, the recession has significantly reduced consumption of aviation kerosene, just as it has reduced consumption of every other form of energy; the US consumed 43,702,000 barrels of jet fuel in September 2010, down about 10% from 2002, and the numbers for January-June 2011 are tracking last year’s statistics.)
That much air traffic produces lots of contrails - enough, it had been theorized, that their collective impact on temperatures ought to be noticeable. The problem was that while the effect of contrails on temperature could be modelled, it wasn’t possible to collect empirical evidence because it wasn’t practical to conduct an experiment - until Al Qaeda conducted it for us. Three scientists - David Travis, Andrew Carleton and Ryan Lauritsen - looked at what happened to daytime and night-time temperatures in the US for the three days that US skies were free of contrails, publishing their results in Nature magazine the following year. What they found was fascinating, but not at all unexpected. Contrails, like (some) clouds, reduce both incoming solar radiation and outgoing infrared radiation, making for warmer days as more sunlight reaches the Earth’s surface, and cooler nights as more heat is radiated to space. In the absence of contrails, the diurnal temperature range (DTR, or the difference between daytime and night-time temperatures) noticeably increased.(Note C)
Incidentally, this concurs with the IPCC, which - perhaps not surprisingly given its inclination in the direction of international controls on fossil fuel consumption - estimates a positive impact on radiative forcing for aircraft contrails (See AR 4, WG1, Chapter 2, Section 2.6 - the estimate is 0.30 Wm-2; note however that the error range for their estimated value is +/- 0.10 to 0.80, or in other words one-third to two and a half times their estimated value. This is scientist-talk for “we really don’t understand how this works”).
Why is the link between contrails and DTR interesting? Well, because it provided empirical confirmation of the obvious but difficult-to-demonstrate contention that clouds have a significant impact on terrestrial temperatures. The current suite of climate models do not incorporate clouds very well; even the IPCC admits to a “low level of scientific understanding” with respect to the forcing effect of clouds on global temperatures.(See AR 4, WG1, Chapter 2, executive summary). As I’ve mentioned in previous CoP messages, this is a rather serious weakness, as slight changes in cloud cover can vastly overwhelm even the grotesquely overestimated radiative forcing (RF) effect attributed to human greenhouse gas emissions. The word “grotesquely”, incidentally, is justified because while global CO2 concentrations have risen remorselessly over the past decade, global temperatures remain well below even the lowest outputs of model scenario runs simulating “zero increase” in emissions. In other words, the models demonstrably and vastly overestimate the role of CO2 in influencing temperatures. But we’ve known that for a long time.
These results are also interesting because they provide an empirical footnote to a paper that was published on 31 August of this year by seven physicists at the University of Belgrade.(Note D) These folks, whose names I’m not going to even try to spell or pronounce, did a study looking at the correlation between cloudiness and Forbush decreases. Those of you with a yen for this sort of thing might remember a CoP I sent out a little over a year ago, on 19 August 2010. Entitled “HAARP and the Climate Wars”, it discussed a number of related topics, one of which was the correlation between a solar coronal mass ejection (CME) monitored by HAARP on 4 August 2010, and a massive drop in cosmic ray flux monitored by the Moscow Neutron Observatory on the same day. This correlation, as I noted at the time, demonstrated the mechanism whereby increases in solar activity lead to reductions in cosmic ray activity - which, as Svensmark has proposed, and as the CERN CLOUD experiment has demonstrated, significantly affects cloud formation in Earth’s atmosphere. The CLOUD experiment, as I reported a few weeks back (“Rays and racists”, 29 August 2011) demonstrated the mechanism using a cloud chamber and a particle accelerator. What the folks at Belgrade U have done is locate empirical evidence for the mechanism in the real world.
A Forbush decrease (FD) is a massive drop in cosmic ray intensity as a result of magnetic activity following a CME - precisely what happened on 4 August 2010 (they’re named after Scott Forbush, a US physicist who studied cosmic rays in the 30’s and 40’s, and appear to have nothing to do with Nellie Forbush, the lead character in the Rogers and Hammerstein musical South Pacific). What the scientists at Belgrade U did was look at correlations between measured FDs and measured changes in cloudiness (note the word “measured”, as opposed to “modelled”). There is plenty of data on both, but only for the modern era; cloudiness data are available from satellite observations for the last two decades, while FDs are detectable principally through changes in cosmic ray intensity (the authors used data from detectors on Mount Washington in the US). The results they obtained demonstrated a correlation between FD events and changes in cloudiness. For smaller FDs, the correlation was hard to see; the effect of changes in cosmic ray intensity on cloudiness tended to get lost in the “noise” of weather. However, the correlation was statistically significant for FDs of larger magnitudes - and the more intense the FD, the larger the average impact on cloudiness.
(Source: A. Dragić, I. Aničin, R. Banjanac, V. Udovičić, D. Joković´, D. Maletić and J. Puzović, “Forbush decreases – clouds relation in the neutron monitor era”, Astrophysics and Space Sciences Transactions, 7, 315–318, 2011)
The upper panel shows the impact on diurnal temperature range of FDs resulting in drops in cosmic ray intensity of 7-10% range (a total of 22 events), while the lower panel shows the impact of FDs resulting in drops in cosmic ray intensity of more than 10% (13 events). As these graphs demonstrate, the larger the Forbush decrease, the greater the impact on cloudiness. This constitutes empirical proof of Svensmark’s proposal that solar activity-moderated galactic cosmic ray flux is a significant driver of atmospheric temperatures.
Criticism of these results from the usual warmist quarters has tended to focus on the fact that in order to detect the correlation, the authors had to “cherry-pick” the largest-magnitude FDs. That’s a canard; the authors looked at all of the results, and determined that the correlation only became significant when the FDs were large. This is because the impact of lower-magnitude FDs is less and tends to get lost in the clutter of terrestrial atmospheric weather patterns, suggesting that weather is a complex interdependent system - something that we’ve known since Lorenz’s modelling work in the 1960s.
So that's more evidence confirming Svensmark, and casting doubt on the IPCC's modelling assumptions. Science is supposed to be about evidence. Hopefully we won’t have occasion in the future to use evidence like that which suddenly became available on 11-14 September 2001 - but it would be criminal to waste it when it’s there.
The University of Belgrade paper is here [http://adsabs.harvard.edu/abs/2011ASTRA...7..315D]. Enjoy!