03 October 2013

Coverage of Extreme Events in the IPCC AR5

I had been scheduled to testify before the House Science Committee next week in a hearing on extreme events, but the gong show in Washington has put that off.

In the process of updating Senate testimony given back in July (here in PDF) I did compile some key statements from the IPCC AR5 WGI Chapter 2 on extremes.

Here are a few:
  • “Overall, the most robust global changes in climate extremes are seen in measures of daily temperature, including to some extent, heat waves. Precipitation extremes also appear to be increasing, but there is large spatial variability"
  • "There is limited evidence of changes in extremes associated with other climate variables since the mid-20th century”
  • “Current datasets indicate no significant observed trends in global tropical cyclone frequency over the past century … No robust trends in annual numbers of tropical storms, hurricanes and major hurricanes counts have been identified over the past 100 years in the North Atlantic basin”
  • “In summary, there continues to be a lack of evidence and thus low confidence regarding the sign of trend in the magnitude and/or frequency of floods on a global scale”
  • “In summary, there is low confidence in observed trends in small-scale severe weather phenomena such as hail and thunderstorms because of historical data inhomogeneities and inadequacies in monitoring systems”
  • “In summary, the current assessment concludes that there is not enough evidence at present to suggest more than low confidence in a global-scale observed trend in drought or dryness (lack of rainfall) since the middle of the 20th century due to lack of direct observations, geographical inconsistencies in the trends, and dependencies of inferred trends on the index choice. Based on updated studies, AR4 conclusions regarding global increasing trends in drought since the 1970s were probably overstated. However, it is likely that the frequency and intensity of drought has increased in the Mediterranean and West Africa and decreased in central North America and north-west Australia since 1950” 
  • “In summary, confidence in large scale changes in the intensity of extreme extratropical cyclones since 1900 is low”
There is really not much more to be said here -- the data says what it says, and what it says is so unavoidably obvious that the IPCC has recognized it in its consensus. 

Of course, I have no doubts that claims will still be made associating floods, drought, hurricanes and tornadoes with human-caused climate change -- Zombie science -- but I am declaring victory in this debate. Climate campaigners would do their movement a favor by getting themselves on the right side of the evidence.


  1. This comment has been removed by a blog administrator.

  2. Roger, you say, " Precipitation extremes also appear to be increasing"

    The word "appear" does not meet your own definition of a scientific statement. Could be Zombie science. If it is not true, don't mention it.

  3. -2-Drug Maven

    Thanks, those are the words of the IPCC.

  4. Dr. Pielke, I don't understand this statement in your testimony.

    "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."

  5. For some reason I couldn't finish that post. What I am asking is what weather extremes you are talking about increasing? The evidence you've presented would seem to contradict this statement unless you mean higher temperatures or something else. Can you quantify the extremes, what they are, at what temperature increase we could expect them and how extreme they will be.

    On a side note I find the IPCC's uses of the terms low confidence and medium confidence to be unnecessary and misleading. The medium confidence indicates 50% meaning they have no idea. I have medium confidence it will get warmer tomorrow, meaning I am just as confident it will get colder. I think a normal person would interpret that statement as meaning you had more confidence than essentially none because people do not talk in that way.
    The low confidence is even worse as it creates a double negative scenario. Saying there is low confidence in increasing floods would normally be spoken as high confidence floods will not increase. Confidence levels should start at 50% and be defined as no confidence and only move upward.

  6. An excellent summary that I'm sure many bloggers will link to.

  7. "The word "appear" does not meet your own definition of a scientific statement. Could be Zombie science. If it is not true, don't mention it. "

    Roger, I meant to say I trust you won't use the word "appear", if and when you testify.

  8. Roger, while you are right to 'declare victory' this should not make one forget the fact that the IPCC has done a bad job at making clear that they have revised their position. This is something which did not make the headlines but which is certainly newsworthy.

  9. Roger "Climate campaigners would do their movement a favor by getting themselves on the right side of the evidence."

    I agree. The thing is that even if they were always on the right side of the evidence, there would still be parties that misrepresent what they are doing. How do you deal with that?

    For example, over at Judith Curry's blog I recently asked the people who comment there if they knew any environmentalists or professional environmentalists. I was prompted to do this after reading many comments that were hostile to environmentalists. I wrote that if they were better aware of what the environmentalist community really is like, a better dialogue could be achieved.

    The subsequent comments just repeated the factually questionable stereotypes of environmentalists.

  10. Um, what about these statements on page 71 of the IPCC WGI 5th Assessment Report (TS.5.8.4):

    Projections for the 21st century indicate that it is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged, concurrent with a likely increase in both global mean tropical cyclone maximum wind speed and rain rates (Figure TS.26). The influence of future climate change on tropical cyclones is likely to vary by region, but there is low confidence in region-specific projections. The frequency of the most intense storms will more likely than not increase substantially in some basins. More extreme precipitation near the centers of tropical cyclones making landfall are likely in North and Central America, East Africa, West, East, South and Southeast Asia as well as in Australia and many Pacific islands. {14.6.1, 14.8.3, 14.8.4, 14.8.7, 14.8.9, 14.8.10, 14.8.11, 14.8.12, 14.8.13, 14.8.14}