Hansen har publisert et draft paper hvor det går klart fram at ekstreme hetebølger som vi så sommeren 2010 i Russland og Texas i 2011 har blitt mer vanlig de senere årene:
Hansen et al (2012):
Perceptions of Climate Change: The New Climate Dice
- "Climate dice", describing the chance of unusually warm or cool seasons relative to climatology, have become progressively "loaded" in the past 30 years, coincident with rapid global warming. The distribution of seasonal mean temperature anomalies has shifted toward higher temperatures and the range of anomalies has increased. An important change is the emergence of a category of summertime extremely hot outliers, more than three standard deviations (σ) warmer than climatology. This hot extreme, which covered much less than 1% of Earth's surface in the period of climatology, now typically covers about 10% of the land area. We conclude that extreme heat waves, such as that in Texas and Oklahoma in 2011 and Moscow in 2010, were "caused" by global warming, because their likelihood was negligible prior to the recent rapid global warming. We discuss practical implications of this substantial, growing climate change.
Forfatterne konkluderer med at slike hetebølger indirekte er forårsaket av global oppvarming, og ikke bare er et resultat av unormalt vær.
Ekstreme hetebølger var praktisk talt et ubetydelige fenomen for noen tiår siden (under 1%), men har de senere årene utgjort 10% av landarealet.
Hansen konkluderer med at et varmere klima allerede nå har betydelig innvirkning på dyre- og planteliv, og at 3°C global oppvarming mot slutten av dette århundret kan true 21-52% av artene på jorda.
- Climate change of recent decades is also having effects on animals, birds and insects that are already noticeable. Although species migrate to stay within climate zones in which they can survive, continued climate shift at the rate of the past three decades is expected to take an enormous toll on planetary life. If global warming approaches 3°C by the end of the century, it is estimated that 21-52% of the species on Earth will be committed to extinction. Fortunately, scenarios are also possible in which such large warming is avoided by placing a rising price on carbon emissions that moves the world to a clean energy future fast enough to limit further global warming to several tenths of a degree Celsius (29). Such a scenario is needed if we are to preserve life as we know it.
Klimaendringene er ikke bare noe som får følger for framtidige generasjoner, men har direkte konsekvenser for både oss mennesker og andre arter allerede nå.
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