The IPCC gives us straight talk about Extreme Weather

Summary:  During the past few years activists have broken free of the climate science consensus of the IPCC, considering it too conservative. This allowed free reign to their imaginations and voices, filling the media with warnings of extreme weather today and worse tomorrow. Once again the IPCC has published, so we can benchmark these threats against the current state of known science. The result is not the simple dramatic story told by activists, but has the advantage of being accurate. Will the news media listen, or continue to promote activists’ alarmism?



  1. Assessing extreme climate threats
  2. A summary of AR5
  3. What the IPCC says about extreme climate change
  4. What the IPCC means by “abrupt” and “irreversible” changes
  5. For More Information

(1)  Assessing extreme climate threats

IPCC’s Fifth Assessment Report (AR5)Working Group 1: The Physical Science Basis

Chapter 12: Long-term Climate Change: Projections, Commitments and Irreversibility

Here is the table that broke a thousand hearts, people who hoped AR5 would support their warnings about the certainty of imminent doom from extreme weather. Newspapers have trumpeted these warnings for years, usually with no mention of their probability. In fact most have lower odds than activists told us. Many oft-mentioned threats did not even make the IPCC’s list. These findings in AR5 mirror those of the IPCC’s March 212 Special Report: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX).

Table 12.4: Components in the Earth system that have been proposed in the literature as potentially being susceptible to abrupt or irreversible change

Column 2 defines whether or not a potential change can be considered to be abrupt under the AR5 definition. Column 3 states whether or not the process is irreversible in the context of abrupt change, and also gives the typical recovery time scales. Column 4 provides an assessment, if possible, of the likelihood of occurrence of abrupt change in the 21st century for the respective components or phenomena within the Earth system, for the scenarios considered in this chapter.

IPCC: Table12-4

What do these probabilities mean?

IPCC Definitions of Probability
Second Order Draft of IPCC’s AR5

(2)  Summary of AR5

For a wider context, here are two key points from a summary by Roger Pielke Jr (Prof Environmental Science, U CO-Boulder):

(1) The core scientific understandings remain unchanged.

The IPCC deserves much praise for bringing to the attention of the public and policy makers the fact that humans influence the climate system and that influence presents some risks. This message represents continuity with past reports. As George Monbiot explains: “There are no radical departures in this report from the previous assessment, published in 2007.” …

(3)  We will not be able to clearly distinguish the influence of that human influence from natural variability for decades

The IPCC SPM explains: “Internal variability will continue to be a major influence on climate, particularly in the near-term and at the regional scale.”

This means that there are exceedingly few variables in which human-caused climate change can be detected and attributed over the coming “short-term” (how long is that?). Apparently we can now add global surface temperatures to that list …

Global Warming
Quite mad propaganda

(3) Excerpts from Chapter 12 about extreme climate change

Excerpts collected by Roger Pielke Jr (Prof Environmental Science, U CO-Boulder):


  • “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”

Specific types of extreme weather:

  • “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, confidence in large scale changes in the intensity of extreme extratropical cyclones since 1900 is low”
  • “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, 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, 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”

(4)  What the IPCC means by “abrupt” and “irreversible” changes

As described at Bishop Hill, comparing the language in AR5 to the common tongue:  “Abrupt changes aren’t really abrupt and irreversible changes aren’t really irreversible.”

12.5.5 Potentially Abrupt or Irreversible Changes Introduction

This report adopts the definition of abrupt climate change used in Synthesis and Assessment Product 3.4 of the U.S. Climate Change Science Program CCSP (CCSP, 2008b). We define abrupt climate change as a large-scale change in the climate system that takes place over a few decades or less, persists (or is anticipated to persist) for at least a few decades, and causes substantial disruptions in human and natural systems …

A number of components or phenomena within the Earth system have been proposed as potentially possessing critical thresholds (sometimes referred to as tipping points, (Lenton et al., 2008)), beyond which abrupt or non-linear transitions to a different state ensues. The term irreversibility is used in various ways in the literature. The AR5 report defines a perturbed state as irreversible on a given timescale if the recovery timescale from this state due to natural processes is significantly longer than the time it takes for the system to reach this perturbed state …

(5)  For More Information

Posts about Extreme Weather:

  1. Climate Armageddon postponed (again): the melting polar ice, 9 October 2010
  2. Looking into the past for guidance about warnings of future climate apocalypses, 17 October 2010
  3. Run from the rising waves! (The latest climate catastrophe scare), 27 June 2012
  4. Ignorance and propaganda about extreme climate change, 10 July 2012
  5. A look behind the curtain at the news of extreme climate events in the US, 22 August 2012
  6. Hurricane Sandy asks when did weather become exceptional? (plus important info about US hurricanes), 28 October 2012
  7. Has global warming increased the frequency & virulence of extreme weather events?, 10 February 2013
  8. The Oklahoma tornadoes can teach us about our climate, and ourselves, 22 May 2013

6 thoughts on “The IPCC gives us straight talk about Extreme Weather”

  1. Pingback: The IPCC gives us straight talk about Extreme Weather - Global Dissident

    1. CartoonMick,

      I do not share your defeatism, nor does history support your bleak use of “always”. The fantastic successes against air and water pollution in the developed nations during the past 50 years show that progress is easy once people decide to make it happen.

      The only way to make your depressing statements come true is to believe them. So please excuse those of us who work to produce a better future despite your advice.

  2. Pingback: Engagement vs communication vs PR vs propaganda | Climate Etc.

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  4. Pingback: When the events of dystopian science fiction becomes media news … | Head Space

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