Pielke Jr asserts, using unvarnished words, that WG2 Co-Chair Christopher Field, an ecology professor at Stanford, “misled” Congress. Pielke stated:
This is not a particularly nuanced or complex issue. What Field says the IPCC says is blantantly wrong, often 180 degrees wrong. It is one thing to disagree about scientific questions, but it is altogether different to fundamentally misrepresent an IPCC report to the US Congress.
Pielke noted in connection with droughts:
Field conveniently neglected in his testimony to mention that one place where droughts have gotten less frequent, less intense or shorter is … the United States.
Field was Co-Chair of the recent IPCC SREX report on Extremes, which reported this fact in unambiguous terms as follows: (p182) [added Aug 2]
In North America, there is medium confidence that there has been an overall slight tendency toward less dryness (wetting trend with more soil moisture and runoff; Table 3-2), although analyses for some subregions also indicate tendencies toward increasing dryness. This assessment is based on several lines of evidence, including simulations with different hydrological models as well as PDSI and CDD estimates (Alexander et al., 2006; Andreadis and Lettenmaier, 2006; van der Schrier et al., 2006a; Kunkel et al., 2008; Sheffield and Wood, 2008a; Dai, 2011). The most severe droughts in the 20th century have occurred in the 1930s and 1950s, where the 1930s Dust Bowl was most intense and the 1950s drought most persistent (Andreadis et al., 2005) in the United States, while in Mexico the 1950s and late 1990s were the driest periods. Recent regional trends toward more severe drought conditions were identified over southern and western Canada, Alaska, and Mexico, with subregional exceptions (Dai, 2011).
Field’s SREX report noted paleoclimate evidence for past megadroughts (which occurred in the US as well) – an important piece of evidence that Field did not disclose in his testimony. [added – Aug 2]
From a paleoclimate perspective recent droughts are not unprecedented, with severe ‘megadroughts’ reported in the paleoclimatic record for Europe, North America, and Australia (Jansen et al., 2007). Recent studies extend this observation to African and Indian droughts (Sinha et al., 2007; Shanahan et al., 2009): much more severe and longer droughts occurred in the past centuries with widespread ecological, political, and socioeconomic consequences. Overall, these studies confirm that in the last millennium several extreme droughts have occurred (Breda and Badeau, 2008; Kallis, 2008; Büntgen et al., 2010).
Tailoring of AR5?
The AR5 Zero Order Draft on paleoclimate stated, in language reminiscent of Soon and Baliunas, “multiple studies suggest that current drought and flood regimes are not unusual within the context of last 1000 years”. However, the First Order Draft was substantially changed to language apparently tailored to avoid a direct contradiction of alarmist narrative.
Watch the pea.
The AR5 Zero Order Draft section on droughts and floods stated:
220.127.116.11 Megadroughts and Floods
Drought and floods are recurring extreme climate events. There is ample historical evidence for their past important physical, economic, social and political consequences (Buckley et al., 2010; Buntgen et al., 2011; Graham et al.; Zhang et al., 2008). Evidence from tree rings, historical documents, stalagmites, lake
sediments, peatlands, etc, indicates that severe megadroughts (by modern standards droughts of unusually long duration that typically exceed those observed in the instrumental records; [Woodhouse and Overpeck, 1998; Stahle et al., 2000; Cook et al., 2010]) are a recurrent feature in many regions including North America, east and south Asia, Europe, Africa and India [(Cook, 2007; Herweijer, 2007; Zhang, 2008; Zheng, 2006; Buckley, 2010; Buckley, 2010; Cook, 2010; Helama, 2009; Russell, 2007; Büntgen, 2010; Esper, 2007; Sinha, 2007; Shanahan, 2009; Neukom, 2010; Pfister, 2006; Touchan, 2008; Touchan, 2010; Pauling, 2007; Verschuren, 2000; Christie, 2009; Berkelhammer, 2010; Nicault et al., 2008)].
The occurrence and spatial extent of past megadroughts may be clustered over time following regime changes. There is evidence for more severe droughts during the LIA in South Asia, eastern Northwest China, and Southeast Asia, west Africa and parts of Europe [(Buckley, 2010; Sinha, 2007; Shao, 2010; Zheng, 2006; Zhang, 2008; Sinha, 2007; Sinha, 2007; Helama, 2009; Buntgen, 2011; Pauling, 2007; Cook, 2010 ; Russell, 2007; Shanahan, 2009)] compared to the predating MCA and the last century. In contrast, drought extent in North America, northern and central Europe, and East Africa were significantly greater during 900–1300 than during the LIA and the last century [(Cook, 2007; Cook, 2010; Herweijer, 2007; Helama, 2009; Luoto, 2010; Russell, 2007; Verschuren, 2000; Stager, 2005)]. Proxy information indicate, that intervals of severe drought in western Africa lasting for periods ranging from decades to centuries are characteristic of the monsoon and are linked to natural variations in Atlantic temperatures ([Shanahan et al., 2009]; see also Sections 18.104.22.168 and 5.6.2). Proxy reconstructions and model experiments suggest that variability in the tropical Pacific might partly account for the occurrence of megadroughts in North America with related teleconnections in all continents (Seager et al., 2008). A strengthening of the zonal SST gradient in the tropical Pacific via an enhancement of La Niña state and possibly warming of the Indian Ocean during periods of the MCA may have contributed to arid conditions in North America (Graham et al.; Seager et al., 2008), contrasting with wetter conditions in Asia (Graham et al., 2007). During the MCA, positive NAO conditions (see Section 22.214.171.124) and AMO phases may have favored wetter winter conditions in NW Europe and arid in NW Africa [(Graham, 2007; Esper, 2007; Touchan, 2008; Touchan, 2010)]. El Niño phases seem to have been more prominent during the LIA than the MCA, in coincidence with monsoon weakening Section 126.96.36.199) and drought occurrence in Asia (Buckley et al., 2010; Cook et al., 2010a),
Overall, multiple studies suggest that current drought and flood regimes are not unusual within the context of last 1000 years [(e.g., Cook et al., 2010; Seager et al., 2008; Graham et al., 2010)].
Now here is the corresponding section of the First Order Draft:
188.8.131.52 Megadroughts and Floods
Paleo drought reconstructions provide estimations of the frequency, duration and severity of past dry periods. Megadroughts are comparable in intensity to present drought events but with durations longer than several years to a decade (e.g., Seager et al., 2009).
Figure 5.12 shows regional PDSI (Palmer Drought Severity Index) values reconstructed using tree rings in North America and Monsoon Asia (Cook et al., 2004; Cook et al., 2010), duration of droughts, their severity, and their frequency. Proxy information indicates that intervals lasting from decades to centuries of more frequent severe drought in western Africa are characteristic of the monsoon and appear to be linked to variations in Atlantic temperatures (Shanahan et al., 2009; see also Section 5.6). Proxy reconstructions and model experiments suggest that strengthening of the zonal SST gradient in the tropical Pacific or more severe La Niña conditions, and possibly warming of the Indian Ocean, during periods of the MCA may have contributed to arid conditions in North America (Graham et al., 2011; Graham et al., 2007; Seager et al., 2008), contrasting with wetter conditions in Asia (Buckley et al., 2010; Graham et al., 2011; Graham et al., 2007), although direct evidence of SST variability and ENSO state is more equivocal (Emile-Geay et al., in press). During the MCA, positive NAO conditions (see Section 184.108.40.206) and AMO phases may have favored wetter winter conditions in NW Europe and arid in NW Africa (Esper et al., 2007b; Graham et al., 2007) although Touchan et al (2011) do not find evidence of overall changes in mean drought conditions in northwestern Africa. The transition from the MCA to the LIA appears to coincide with monsoon weakening and megadrought occurrence in Asia (Buckley et al., 2010; Cook et al., 2010), while in North America an apparent shift toward overall wetter conditions occurs in the middle of the 14th century (Cook et al., 2004).
Overall, multiple studies suggest that current flood magnitudes are not unusual within the context of the last 1000 years (e.g., Benito et al., 2011; Brázdil et al., 2012; Enzel et al., 1993; Greenbaum et al., 2000; Herget and Meurs, 2010; Mudelsee et al., 2003)…
Note carefully that the First Order Draft suppressed any explicit mention of historical megadroughts exceeding those in the modern instrumental record (attested in the Zero Draft by a substantial literature. In my opinion, the language in the Zero Order Draft was a better assessment of paleoclimate information.
What was the justification for IPCC authors removing this important information from paleoclimate? It appears to me that the information was deleted because it was inconsistent with alarmist narrative on droughts and not for a valid reason.
To borrow a phrase from Phil Jones, one might say that the evasive language of the First Order Draft was a trick to hide the megadroughts.
Postscript: In Field’s day job, he does statistical analyses of crop yields. His main claim to fame is arguing that increased temperatures have reduced crop yields. Given the astronomical increase in crop yields during the 20th century concurrent with temperature increases and many confounding factors, this is an uphill job. Field’s frequent coauthor, David Lobell, attracted attention with an article in Science last year, expanding on this point. I looked briefly at that article (but did not post on it.) I was amused that it used the CRU-TS data set excoriated by Harry-Readme. (As I recall, the harry readme was explained away on the basis that no one used the CRU-TS data set, a memo that Field and coauthors do not appear to have received.)