Streetwise Professor

August 28, 2010

Under Pressure

Filed under: Climate Change,Politics — The Professor @ 8:58 pm

This is, in a way, a woulda, coulda, shoulda post.  Back in July I was going to write about the Russian heatwave by referring to a book on climatology that (a) seemed to provide a cogent explanation of the process by which a brutal heat wave could be created, and (b) strenuously argued that this process had nothing to do with anthropogenic global warming.  But other stuff happened, the post didn’t get written–and now the National Oceanic and Atmospheric Administration (NOAA) has released a report validating this explanation of the heat wave.  Thus, I could have said I told you so.  But I didn’t.  So you can take me at my word that I indeed could have said so, or not, depending on your predisposition.

Anyways, during the height of the Russian heat wave, I immediately thought of the book “Global Warming: Myth or Reality?  The Erring Ways of Climatology” by the late Marcel Leroux, a well-known (and iconoclastic) French climatologist.  (I read the book in the fall of 2006.  I’ve mentioned it on the blog before.)  Leroux emphasized the decisive influence of “mobile polar highs”–high pressure cells originating at the poles, then moving towards the equator–in determining weather and climate.  With respect to heat waves in particular, Leroux argued that “anticyclonic agglutinations”–combinations of a sequence of MPHs–were to blame.  When an unusually strong series of MPHs combine, and then stall over a particular region, during periods of high insolation (i.e., the summer) that area will experience a heat wave.  Describing the infamous French heat wave of 2003, Leroux wrote:

In 2003, from June onwards, the meteorological situation was dominated . . . by th epresence of a vast area of high pressure. . . . The great stability brought about by the anticyclonic conditions–calm air, or very slight breezes, and the absence of upward air movements–encouraged the warming of air in the lower layers.  The conduction of heat, and infrared absorption, are in fact enhanced when pressures are high and the air cannot rise; the layers nearest to the ground become (for the same amount of solar energy received) relatively very much warmer.  The heating leads to a considerable diminution of relative humidity (i.e., the air becomes much drier).  . . . Now that the moisture content is absent, maximum insolation occurs, and the cumulative heating effect gradually assumes the proportions of a ‘heatwave’, especially in urban areas, which are less ‘ventilated’, and become warmer, drier, and more polluted (pp. 278-279).

When re-reading Leroux in July, that sounded to me exactly like what happened in central Russia, down to the last jot.

Recently NOAA, hardly a hotbed of climate change skepticism, has stated that the Russian heatwave fits the Leroux template exactly:

The extreme surface warmth over western Russia during July and early August is mostly a product of the strong and persistent blocking high. Surface temperatures have soared as a result of the combination of clear skies, sinking motion within the environment of the high pressure causing compressional heating of air, the lack of any temporary relief owing to the blocking of the typical cold fronts that cool the region intermittently in summer. Add to this scenario the cumulative effect of drought that began in early summer which has caused soils to dry and plants to desiccate to wilting point , thereby causing additional surface warming via land feedbacks as the blocking condition persisted. These are all well-known and studied physical processes that have accompanied summertime blocking and heat waves in the past.

Much of the intensity of the current heat wave, and also the pattern of surface temperature conditions across Eurasia during July 2010, can be recreated from the atmospheric blocking event itself. The diagnostic procedure involves standard methods applied to the historical record of analyzed 500 mb heights and surface temperatures during the prior period of 1900-2008. The method of statistical regression is used to understand how surface temperature changes during a typical blocking occurrence over Russia during July, and is a method that can be used to infer causal relationships.

The temperature pattern accompanying a “garden variety” block consists of a localized +1 to +2°C warming over western Russia, with somewhat weaker coolness toward the Urals. July 2010 was not a garden variety block, but was instead the most extreme block in the post-1900 period. While there is no analogue from which to draw an assessment of the expected impact on temperatures form such a block, one can nonetheless use the historical regression relation in order to infer the impact of this extreme July 2010 block. The process involves multiplying the regression pattern by the standardized departure of the height index observed for July 2010. The calculation offers a meaningful evaluation of the surface temperature response to the extent that the height-temperature relation is linear. The results indicate a surface warming in excess of +5°C is expected over western Russia in response to the July 2010 blocking high, accompanied by a downstream pattern of about -3°C coolness over the Urals and warmth of +2°C to +3*C over northern China, Mongolia, and northeastern Russia.

The comparison of the above reqression map with the observed temperature anomaly map for July 2010 clarifies the cause for this heat wave. The strong agreement between the July 2010 observed pattern of Eurasian surface temperatures and that pattern attributable to the impact of upper tropospheric blocking provides key evidence that the block is the immediate cause for the heat wave (and related temperature conditions over adjacent countries). Blocking events are typically of 1-2 week duration, and by contrast the 2010 situation is highly unusual in that blocking has existed over western Russia on virtually every day form the beginning of July until the middle of August. The cumulative impact of such prolonged blocking has led to the extreme nature of the surface impacts on temperature, soil conditions, and rainfall.

The near universal response to the Russian heat wave has been–I’m sure you’re surprised–to attribute it to global warming, or climate change, or whatever the nom de jour might be.  This continues even after NOAA weighed in, with drivel like this in the FT.

To attribute this to a secular global temperature rise, it would be necessary to show how such a rise would affect the likelihood and severity of such “blocking events” (anticyclonic agglutinations in Leroux’s terms).  Leroux said it could not be done, generally, and indeed was nonsensical: if a rise in temperatures (forced by GHGs) was the underlying mechanism, pressures should drop (p. 279) because, duh, hot air rises–unless the rise is blocked by a high pressure wave resulting from some other process.  (Other climate skeptics, notably Richard Lindzen, postulate that the rising hot air results in a negative feedback mechanism that substantially reduces the temperature increase resulting from a given increase in GHGs.)

Moreover, NOAA refuses to attribute the blocking events to a secular climate change process:

Despite this strong evidence for a warming planet, greenhouse gas forcing fails to explain the 2010 heat wave over western Russia. The natural process of atmospheric blocking, and the climate impacts induced by such blocking, are the principal cause for this heat wave. It is not known whether, or to what exent, greenhouse gas emissions may affect the frequency or intensity of blocking during summer. It is important to note that observations reveal no trend in a daily frequency of July blocking over the period since 1948, nor is there an appreciable trend in the absolute values of upper tropospheric summertime heights over western Russia for the period since 1900.

The indications are that the current blocking event is intrinsic to the natural variability of summer climate in this region, a region which has a climatological vulnerability to blocking and associated heat waves (e.g., 1960, 1972, 1988). A high index value for blocking days is not a necessary condition for high July surface temperature over western Russia—the warm summers of 1981, 1999, 2001, and 2002 did not experience an unusual number of blocking days.

It should also be noted that the warming was extremely localized, that the Southern Hemisphere actually experienced substantial cooling, and the pattern observed in 2010 was less “global” than the pattern during the comparable event in Russia during the summer of 1936.

The contrasting patterns in parts of the Northern and Southern Hemispheres suggests to me that one of the various periodicities in climate may be at work, but that’s just a wild guess on my part.

The temptation to use weather events to flog pet theories about climate is dishonest an annoying in the extreme–regardless of who does it, be they skeptics jumping up and down about a cold winter or alarmists howling about a hot summer.  The Jeremiah-esque ideologue and proselytizer James Hanson got the global warming hysteria ball rolling by saying that the US heatwave and drought of 1988 was a harbinger of doom–when it was most likely something quite similar to what happened in Russia this summer.  Their cause flagging politically, the alarmists are trying to do the same with the Russian heat wave.  It is not honest to do so–and it is not science.

It is possible that there are complex interactions and mechanisms by which temperature trends forced by GHGs can lead to increased frequencies and intensities of heatwaves and droughts.  But none have been described or tested.  The initial empirical evidence, per NOAA, that there appears to be no trend in the frequency of blocking events is inconsistent with this.  Moreover, as Leroux notes, atmospheric pressure and the frequency of MPHs both began to trend up well before GHGs did.  So what caused that pressure trend?  GHGs couldn’t have.

Thus, the Russian heatwave should be a reason to acknowledge that we do not fully understand–or even remotely understand–the drivers of temperature extremes in particular, or climate generally.  It should be a spur to inquiry and research, not an opportunity to advance predetermined agendas.

NOAA is to be commended for taking an objective approach to the subject.  Sadly, too few others–including far too many scientists–have not.  Rather than a centerpiece of a morality play about global warming, events like the Russian heat wave should be viewed as things that are anomalies (or at least, lacunae) in the received climate models.  Such anomalies/lacunae should lead to questioning the received models, and the posing and testing of others.  That’s how science should work.  Whether today’s politicized climate science will work that way is, sad to say, highly doubtful.

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1 Comment »

  1. […] Good piece here. […]

    Pingback by Russian heatwave: not climate change, NOAA says so — August 29, 2010 @ 6:13 am

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