Mar 29, 2012

Perception of climate change

James Hansen, Makiko Sato, Reto Ruedy
Proceedings of the National Academy of Sciences
  • States that “climate dice,” describing the chance of unusually warm or cool seasons, have become more and more “loaded” in the past 30 y, coincident with rapid global warming
  • Finds the distribution of seasonal mean temperature anomalies has shifted toward higher temperatures and the range of anomalies has increased
  • Finds an important change is the emergence of a category of summertime extremely hot outliers, more than three standard deviations (3σ) warmer than the climatology of the 1951–1980 base period
  • Holds that this hot extreme, which covered much less than 1% of Earth’s surface during the base period, now typically covers about 10% of the land area
  • Says it follows that we can state, with a high degree of confidence, that extreme anomalies such as those in Texas and Oklahoma in 2011 and Moscow in 2010 were a consequence of global warming because their likelihood in the absence of global warming was exceedingly small
  • Discusses the practical implications of this substantial, growing, climate change