Excerpts from the leaked AR5 Summary for Policy Makers

I’ve been given a copy of the “leaked” AR5 SPM, which has been widely circulated and cited in advance in the MSM, but I’ve just now been able to get a copy.  Reportedly, there are some 1800 changes requested by government participants in the upcoming meeting to hammer out the final version, so it is doubtful that what I’m posting below will be the same as the final.

Still we need a baseline for comparison, and now I have one, so that will be a future post. These are a few things that caught my eye. I’ll post them as time permits, and I don’t have time to comment today as I have other pressing issues.

First, there doesn’t appear to be a single skeptic (correct me if I’m wrong) in the author list.

Atmosphere

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3 Each of the last three decades has been warmer than all preceding decades since 1850 and the first decade of

4 the 21st century has been the warmest (see Figure SPM.1). Analyses of paleoclimate archives indicate that in

5 the Northern Hemisphere, the period 1983–2012 was very likely the warmest 30-year period of the last 800

6 years (high confidence) and likely the warmest 30-year period of the last 1400 years (medium confidence).

7 {2.4, 5.3}

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10 [INSERT FIGURE SPM.1 HERE]

11 Figure SPM.1: (a) Observed global mean combined land and ocean temperature anomalies from three surface

12 temperature data sets (black – HadCRUT4, yellow – MLOST, blue – GISS). Top panel: annual mean values, bottom

13 panel: decadal mean values including the estimate of uncertainty for HadCRUT4. Anomalies are relative to the mean of

14 1961−1990. (b) Map of the observed temperature change from 1901−2012derived from temperature trends determined

15 by linear regression of the MLOST time series. Trends have been calculated only for grid boxes with greater than 70%

16 complete records and more than 20% data availability in the first and last 10% of the time period. Grid boxes where the

17 trend is significant at the 10% level are indicated by a + sign. {Figures 2.19–2.21; Figure TS.2}

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20 • The globally averaged combined land and ocean surface temperature data show an increase of 0.89

21 [0.69 to 1.08] °C 3 over the period 1901–2012. Over this period almost the entire globe has experienced

22 surface warming. (Figure SPM.1). {2.4.3}

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24 • Global mean surface temperature trends exhibit substantial decadal variability, despite the robust multi-

25 decadal warming since 1901 (Figure SPM 1). The rate of warming over the past 15 years (1998−2012;

26 0.05 [−0.05 to +0.15] °C per decade) is smaller than the trend since 1951 (1951−2012; 0.12 [0.08 to

27 0.14] °C per decade). (Figure SPM.1) {2.4.3}

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29 • Continental-scale surface temperature reconstructions show, with high confidence, multi-decadal

30 intervals during the Medieval Climate Anomaly (950−1250) that were in some regions as warm as in

31 the late 20th century. These intervals did not occur as coherently across seasons and regions as the

32 warming in the late 20th century (high confidence). {5.3.5, 5.5.1}

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34 • It is virtually certain that globally the troposphere has warmed and the stratosphere has cooled since the

35 mid-20th century. There is medium confidence in the rate of change and its vertical structure in the

36 Northern Hemisphere extra-tropical troposphere and low confidence elsewhere. {2.4.4}

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38 • Because of data insufficiency, confidence in precipitation change averaged over global land areas since

39 1901 is low prior to 1950 and medium afterwards. The incomplete records show mixed and non-

40 significant long-term trends in global mean changes. Precipitation has increased in the mid-latitude land

41 areas of the Northern Hemisphere since 1901 (medium confidence prior to 1950 and high confidence

42 afterwards). {2.5.1}

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44 • Changes in many extreme weather and climate events have been observed since about 1950 (see Table

45 SPM.1). It is very likely that the number of cold days and nights has decreased and the number of warm

46 days and nights has increased on the global scale. In some regions, it is likely that the frequency of heat

47 waves has increased. There are likely more land regions where the number of heavy precipitation events

48 has increased than where it has decreased. Regional trends vary, but confidence is highest for North

49 America with very likely trends towards heavier precipitation events. {2.6.1, 2.6.2; FAQ 2.2}

3 In the WGI contribution to the AR5, uncertainty is quantified using 90% uncertainty intervals unless otherwise stated. The 90% uncertainty interval, reported in square brackets, is expected to have a 90% likelihood of covering the value that is being estimated. The upper endpoint of the uncertainty interval has a 95% likelihood of exceeding the value that is being estimated and the lower endpoint has a 95% likelihood of being less than that value. A best estimate of that value is also given where available. Uncertainty intervals are not necessarily symmetric about the corresponding best estimate.