As a continuation of the IPCC’s observation (2013) that there has been no detectable trend in storm and cyclone intensification (or extreme weather in general) that can be clearly linked to rising anthropogenic CO2 emissions, a new paper documents the rapid decline in eddy kinetic (EKE) and mean available potential energy (MAPE) since the late 1970s. This undermines the popularized claims that human activity worsens extreme weather events.
Image Source: Gertler and O’Gorman, 2019
In Chapter 2 of the 5th assessment report, the Intergovernmental Panel on Climate Change (IPCC) documented a lack of any detectable global trends in extreme weather events, including cyclone intensities, during the “anthropogenic climate change” era.
Quotations Source: IPCC, 2013
In recent years, in fact, there have been several papers indicating that climate warming has the effect of decreasing storm and cyclone intensities and frequencies, or stabilizing weather patterns.
Image Sources: Chang et al., 2016 and Sugi et al., 2015
Image Source: Laliberté et al., 2015
A new paper published in PNAS this past week further affirms that the available energy powering storm activity has dramatically weakened since 1979.
Image Source: Gertler and O’Gorman, 2019
This new paper can be added to the long list of recent scientific publications indicating that storms and cyclone activity has been declining in recent decades.
“The extremely active 2017 Atlantic hurricane season concluded an extended period of quiescent continental United States tropical cyclone landfall activity that began in 2006, commonly referred to as the landfall drought. We introduce an extended climatology of U.S. tropical cyclone activity based on accumulated cyclone energy (ACE) and use this data set to investigate variability and trends in landfall activity. The [hurricane landfall] drought years between 2006 and 2016 recorded an average value of total annual ACE [accumulated cyclone energy] over the U.S. that was less than 60% of the 1900–2017 average.”
“Scaling this landfall activity metric by basin-wide activity reveals a statistically significant downward trend since 1950, with the percentage of total Atlantic ACE expended over the continental U.S. at a series minimum during the recent drought period.”
“Continental United States (CONUS) hurricane-related inflation-adjusted damage has increased significantly since 1900. However, since 1900 neither observed CONUS [Continental United States] landfalling hurricane frequency nor intensity show significant trends, including the devastating 2017 season.”
“Over the 1997–2014 period, the mean frequency of western North Pacific (WNP) tropical cyclones (TCs) was markedly lower (~18%) than the period 1980–1996. Here we show that these changes were driven by an intensification of the vertical wind shear in the southeastern/eastern WNP tied to the changes in the Walker circulation, which arose primarily in response to the enhanced sea surface temperature (SST) warming in the North Atlantic, while the SST anomalies associated with the negative phase of the Pacific Decadal Oscillation in the tropical Pacific and the anthropogenic forcing play only secondary roles.”
“A vigorous debate has currently focused on the relationship between increasing TC [tropical cyclone] activity and increasing SST [sea surface temperatures] (Knutson et al. 2010). … [O]ver the WNP [Western North Pacific] basin, a significant decrease of TCF [tropical cyclone frequency] has been observed since 1998 (Liu and Chan 2013; Lin and Chan 2015; Zhao and Wang 2016). Global TCF [tropical cyclone frequency] has showed a similar reduction since the late 1990s (Maue 2011). Change of TCF over the past few decades does not appear to be consistent with changes in local SST. Observational analyses further pointed out that there is no significant correlation between the TCF [tropical cyclone frequency] and local SST [sea surface temperatures] over the WNP [Western North Pacific] basin (Chan 2006; Yeh et al. 2010).”