La Global Warming Policy Foundation (GWPF), think tank di policy climatiche, ha diffuso appena qualche giorno fa un documento che affronta in modo piuttosto estensivo il collegamento tra cambiamenti climatici ed eventi estremi.
E’ una lettura interessante, che sfata molti miti decisamente cari all’informazione mediatica e all’attivismo climatico, ribadisce quanto scritto (ma letto da pochi) nei recenti report dell’IPCC sull’argomento in questione e mette in risalto come potrebbe essere un clima più freddo – ove con esso si identifichi il funzionamento dell’intero sistema – e non uno più caldo a far salire le probabilità che gli eventi atmosferici aumentino di intensità e frequenza di occorrenza, come del resto sembrano testimoniare le pur farraginose informazioni relative al passato di cui si dispone.
Quelli che seguono sono i punti con cui viene riassunto il discorso al termine del documento:
- Extreme weather events are an inherent aspect of the Earth’s climate system.
- Extreme weather events have occurred throughout the recorded history of the Earth’s climate.
- The Earth’s climate warmed quickly during the first half of the twentieth century. In North America, the decades of 1920s and 1930s, known as the dustbowl years, witnessed extremes of climate, with recurring droughts and heatwaves.
- During the period 1945–1977 when the mean temperature of the Earth declined by about 0.25°C, there were a number of notable (and tragic) extreme weather events. Most climate scientists attributed these extreme weather events to natural climate variability.
- Many climate scientists and environmentalists have attributed recent extreme weather events to the warming of the Earth’s climate. However, this attribution is not substantiated at this point in time. A careful assessment of many wellpublicized extreme weather events of the last ten years suggests that they are due to natural climate variability.
- Hurricanes and tropical storms do not show increasing trends in frequency or in
- When closely examined there appears to be no increase in extreme weather events in recent years compared to the period 1945–77, when the Earth’s mean temperature was declining. The global warming/extreme weather link is more a perception than reality (Khandekar et al. 2005). The purported warming/extreme weather link has been fostered by increased and uncritical media attention to recent extreme weather events. The latest IPCC documents appear to deemphasize the warming/extreme weather link by suggesting ‘low confidence’ in linking some of the events to recent warming of the climate.
- Cold weather extremes have definitely increased in recent years; for example, the severe winters in Europe (2012/13, 2011/12, 2009/10) and North America (2012/13, 2007/08). There have also been colder winters in parts of Asia (2012/13, 2002/03) and South America (2007, 2010 and 2013).
- The Earth’s climate may witness cold as well as warm weather extremes in future
(between now and 2025).