Natural Variability Domination: Defying Models, Scientists Find LESS Extreme Precipitation In Recent Decades
By Kenneth Richard
Higher frequencies of drought and extreme rainfall are assumed to be associated with modern climate change. But long-term studies in both hemispheres indicate extreme precipitation patterns were more common prior to the 20th and 21st centuries. Natural variability dominates precipitation patterns so thoroughly that an anthropogenic signal cannot be detected in observed records.
Internal climate variability (ICV) masks detection of an anthropogenic influence in extreme rainfall patterns (Bhatia and Ganguly, 2019).
Image Source: Bhatia and Ganguly, 2019
Contrary to modeled expectations, there has been no “coherent picture” of an increase in extreme precipitation on a global scale in recent decades (Tabari and Willems, 2018).
Image Source: Tabari and Willems, 2018
There has been “little unequivocal evidence” of an acceleration of the hydrological cycle on a global scale in recent decades. Instead, recent trends are “caused by internal climate variability” (Miralles et al., 2016).
Image Source: Miralles et al., 2016
“No evidence was found for changes in extreme precipitation attributable to climate change in the available observed record” (van der Wiel et a., 2016).
Image Source: van der Wiel et a., 2016
“Natural variability appears to dominate current observed trends” in precipitation extremes (Kendon et al., 2018).
Image Source: Kendon et al., 2018
Since 1983, there has been no increasing or decreasing trends in precipitation detected on a global scale (Nguyen et al., 2018).
Image Source: Nguyen et al., 2018
There have been “no significant trends” in extreme precipitation (floods or droughts) on the East and West US coasts observed in the last 145 years. Further, “significant drought conditions that were common prior to 1900 have not been experienced by the present population“(Christy, 2019).
Image Source: Christy, 2019
Image Source: Jiang et al., 2019
Not warm, but “cold tropical Pacific Ocean conditions are the principal driver of pan-[continental United States] droughts” (Baek et al., 2019).
Image Source: Baek et al., 2019
For Antarctica as a whole, “there has been no significant change in the precipitation from EPEs [extreme precipitation events] over the period considered here [1979-2016]” (Turner et al., 2019).
Image Source: Turner et al., 2019
An intensification of the hydrological cycle – the wet-gets-wetter-dry-gets-drier paradigm – was more evident prior to the 20th century according to Northern Hemisphere proxy evidence over the last 1200 years (Ljungqvist et al., 2016).
Image Source: Ljungqvist et al., 2016
Megadroughts and flood events “were more severe, extensive, and prolonged over Northern Hemisphere land areas before the 20th century” (Cook et al., 2015).
Image Source: Cook et al., 2015
For the Southern Hemisphere (Australia), extreme patterns in drought and flood events were “signficantly longer and more frequent” prior to 1900 (Tozer et al., 2016).
Image Source: Tozer et al., 2016
Extreme daily rainfall events were “more extreme [during 1839-1899] than anything in the modern record” for the Australian cities of Melbourne, Sydney, and Adelaide (Ashcroft et al., 2019).