TCS Daily

Facts Are in Fashion in Milan

By Willie Soon - December 3, 2002 12:00 AM

World delegates are assembling at the city of Milan from December 1 through 12 for the ninth session of the UN Framework Convention on Climate Change Conference of the Parties (COP-9) meeting. The official agenda of COP-9 ranges from the top-level matters related to the Kyoto Protocol and its intricate details, to the more mundane house-keeping matters like the request from a group of countries of Central Asia and the Caucasus, Albania and the Republic of Moldova regarding their status under the Convention.


But much more important is the question of climate science from and about -- Milan.

Figure 1 below points to the climatological fact that the city of Milan is an urban heat island. Over the past 200 years, Milan has grown significantly and is now the second largest Italian city after Rome. It has expanded[1] significantly from what it was in 1800 AD, modifying its pre-industrial landscape with tar, asphalt, brick, concrete and so on. The result is that the temperature of Milan as recorded at the Brera Astronomical Observatory -- which keeps the longest available record in Milan (see the location indicated in Figure 1) -- is artificially elevated by as much as 2C when compared to the temperatures during the 19th century.



Figure 1: The growth of the city of Milan from 1800 AD with 110,000 inhabitants to 1940 AD with 1.37 million inhabitants. The central location of the Brera Astronomical Observatory where the longest temperature record of Milan is kept is also indicated in panel (d). The whitened area in the center of panel (d) for 1940 is a reproduction of Milan during the 1800 AD shown in panel (a). [Adapted from Maugeri et al., 2002, Climatic Change, vol. 53, 119-149]


Figure 2 shows that upon correction of the urban heat island bias,[2] the yearly mean temperatures of Milan from 1763 to 1998 do not suggest any unprecedented warming or change during the 20th century. The 20th century is of course exactly the time when the worlds atmospheric CO2 content is rising by about 28% from its pre-industrial level. The added CO2, argue proponents of the Kyoto Protocol, should be introducing weather and climate havoc and disasters in the world.




Figure 2: After correction for the historical growth of the city, the yearly mean temperatures of Milan from 1763-1998 show no especially exceptional warming during the 20th century. [Adapted from Maugeri et al., 2002, Climatic Change, vol. 53, 119-149]


What about climate from the broader region of Italy?


Professor Walter Dragoni of Perugia University, Professor Maurizo Maugeri of University of Milan and Dr. Michele Brunetti of Bologna University and colleagues have published several recent research papers and there are two key points worth highlighting:


(1)     Climate in Italy (based on indirect climate indicators like lake level, position or size of glacier, tree-ring width, etc.) has generally been alternating between warm-dry and cool-wet periods each lasting a few hundred years during the last 3000 years.


(2)     Italian climate (based on instrumental records covering all climatic zones from both the northern and southern Italy) is becoming warmer and drier in the last 100-150 years, much like those during the late Holocene [i.e: last several thousand years]. An increase of heavy precipitation events and long dry spells are also noted and they are related to recent changes in atmospheric circulation pattern.


Figure 3 shows partial evidence supporting the fact that large climatic swings have been rather common in the Italian climatic records based. It is based on an upcoming paper in the important scientific journal Global and Planetary Change by Dr. Guglielmin Mauro of University of Insubria. The chart describes the ground surface temperatures near the mountain site Stelvio in the Italian Central Alps at a height of 3000 meters for the past 200 years. The ground surface temperature at Stelvio shows that a rapid cooling sets in since 1800 leading to a maximum glacial advance around the Italian Central Alps region by the 1820s. That cool-wet condition is maintained for at least 100 years before warming began around 1940. Warmth peaked around1978. Surprisingly, glaciers around the region re-advanced until the mid-1990s. Dr. Mauro also noted the temperature history in Stelvio largely agrees with the ground surface temperature data deduced from a borehole located as far north as Svalbard, except that the modern glacial advance event (or Neo Glacial as marked in Figure 3) started in the 1960s at Svalbard rather than 1978 (as in Stelvio).



Figure 3: The mean annual ground surface temperature history from a borehole drilled near the Livio glacier cable car station Stelvio (at an altitude of 3000 meters) showing a rapid advance of glaciers from 1978 till middle of 1990s or so.  [Adapted from Mauro, 2003, Global Planetary Change, vol. 40, in press]



Are the onset of warming after the mid-1990s in Figure 3 and those recent changes in atmospheric circulation noted in key point # (2) above CO2 related? The hydro-geologist Walter Dragoni from Perugia University says:



From a methodological point of view, it seems difficult to attribute for certain the present climatic variation to the anthropogenic greenhouse effect, as climatic changes have happened in the recent past without mans intervention. The proxy data indicates that, during the last 3,000 years, non-anthropogenically caused climatic variations [are] larger than those embodied in our instrumental data sets.


In other words, statistics gleaned from Italian climate records do not support the simplistic view of climate and climatic change embedded in the action items of the Kyoto Protocol to cut carbon dioxide emissions immediately. Climate varies naturally without carbon dioxide forcing. Even stopping human CO2 emissions completely would not insure us against the reality of large climatic variations likely to operate over time scales of several decades to centuries. Climate records from Milan and Italy may have spoken clearly, but will most participants of the ongoing COP-9 meeting in Milan hear?




[1] The metropolitan area of Milan consists of a total of 187 municipalities (including the provincial capital Milan) that carry a total of about 3.75 millions inhabitants (of which 1.369 millions in the city of Milan and 2.369 millions in the rest of the municipalities).

2 Full details of this remarkable work are presented by Professor Maurizo Maugeri of the Universit degli Studi di Milano and his colleague in their paper cited above. But it should be noted that population growth is only one factor for the correction of this heat island bias. Additional factors to account for the changes in the environment around the thermometers include microclimate in the meteorological screen and its change in its management and increases and modification of the Brera [Observatory] building.


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