2013 Climate Change Review

Roger Pielke Jr. has an excellent summary on the “state of climate change”, (view the article), given in his testimony to the House last week. The full testimony is posted here, with some of the highlights below. Also, there is an interesting confrontation item by item on the mistakes of the last IPCC assessment for anyone who is looking for more detail. Bottom line, there is no evidence for an increase in weather disasters. Bellow, the highlights:

Take-Home Points

  •   There exists exceedingly little scientific support for claims found in the media and political debate that hurricanes, tornadoes, floods and drought have increased in frequency or intensity on climate timescales either in the United States or globally.1
  •   Similarly, on climate timescales it is incorrect to link the increasing costs of disasters with the emission of greenhouse gases.
  •   These conclusions are supported by a broad scientific consensus, including that recently reported by the Intergovernmental Panel on Climate Change (IPCC) in its fifth assessment report (2013) as well as in its recent special report on extreme events (2012).

To avoid any confusion

Because the climate issue is so deeply politicized, it is necessary to include several statements beyond those reported above.

  •   Humans influence the climate system in profound ways, including through the emission of carbon dioxide via the combustion of fossil fuels.4
  •   Researchers have detected and (in some cases) attributed a human influence in other measures of climate extremes beyond those discussed in this testimony, including surface temperatures (heat waves) and in some measures of precipitation.5
  •   The inability to detect and attribute increasing trends in the incidence of hurricanes, floods, tornadoes and drought does not mean that human-caused climate change is not real or of concern.
  •   It does mean however that some activists, politicians, journalists, corporate and government agency representatives and even scientists who should know better have made claims that are unsupportable based on evidence and research.
  •   Such claims could undermine the credibility of arguments for action on climate change, and to the extent that such false claims confuse those who make decisions related to extreme events, they could lead to poor decision making.
  •   A considerable body of research projects that various extremes may become more frequent and/or intense in the future as a direct consequence of the human emission of carbon dioxide.6
  •   Our research, and that of others, suggests that assuming that these projections are accurate, it will be many decades, perhaps longer, before the signal of human-caused climate change can be detected in the statistics of hurricanes (and to the extent that statistical properties are similar, in floods, tornadoes, drought).7

    The remainder of this written testimony provides data and references to support the claims made in the “take-home points” above. The “take-home points” are broadly supported by peer-reviewed research, US governmental assessments of climate science and the recent reports of the Intergovernmental Panel on Climate Change, specifically its Special Report on Extreme Events (IPCC SREX 2012) and its recently-released Working Group I report of its fifth assessment.8

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