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)."
"The hurricane analysis conducted by Burn and Palmer (2015) determined that hurricane activity was subdued during the [warm] Medieval Climate Anomaly (MCA) (~900-1350 CE) and became more produced during the [cold] Little Ice Age (LIA) (~1450-1850 CE), followed by a period of variability occurred between ~1850 and ~1900 before entering another subdued state during the industrial period (~1950-2000 CE). In general, the results of this study corroborate these findings."
"[W]hile hurricane activity was greater during the LIA, it also had more frequent periods of drought compared to the MCA (Burn and Palmer 2014), suggesting that climate fluctuations were more pronounced in the LIA compared to the MCA. The changes in the diatom distribution and fluctuations in chl-a recorded in this study starting around 1350 also indicate that variations in climate have become more distinct during the LIA and from ~1850-1900. … [C]limate variability has increased following the onset of the Little Ice Age (~1450-1850 CE), however it is difficult to distinguish the impacts of recent anthropogenic climate warming on hurricane activity from those of natural Atlantic climate regimes, such as ENSO."
"Since the late 1800s, in contrast to much of the Southeastern USA, the Georgia coast has experienced infrequent hurricane landfalls, particularly in recent decades. As a result, coastal storm preparedness complacency appears to be rampant along the Georgia coastline. Both local and state governments were unprepared for shadow evacuation during Hurricane Floyd in 1999. The study described here includes an examination of temporal and spatial trends in hurricane landfall along the Georgia coast from 1750 to 2012. Since 1750, 18 of the 24 recorded hurricanes that made landfall along the Georgia coast occurred between 1801 and 1900, yet the hurricane intensities have declined since 1851."
"The Tibetan Plateau (TP), one of the world's most sensitive areas to climate change, became significantly warmer during recent decades. Since 1960 (1980), storm (hail) days have been decreasing by 6.2%/decade (18.3%/decade) in the region."
"Based on 53‐year continuous weather records at 48 TP stations and reanalysis data, we show here for the first time that the consistent decline of storm days is strongly related to a drier midtroposphere since 1960. Further analysis demonstrated that fewer hail days are driven by an elevation of the melting level (thermodynamically) and a weaker wind shear (dynamically) in a warming climate. These results imply that less storm and hail may occur over TP when climate warms."
"Based on continuous and coherent severe weather reports from over 500 manned stations, for the first time, this study shows a significant decreasing trend in severe weather occurrence across China during the past five decades. The total number of severe weather days that have either thunderstorm, hail and/or damaging wind decrease about 50% from 1961 to 2010. It is further shown that the reduction in severe weather occurrences correlates strongly with the weakening of East Asian summer monsoon which is the primary source of moisture and dynamic forcing conducive for warm-season severe weather over China."
"Results indicate that the midlatitude summer cyclone activity over East Asia exhibits decadal changes in the period of 1979–2013 and is significantly weakened after early 1990s. … Moreover, there is a close linkage between the weakening of cyclonic activity after the early 1990s and the nonuniform surface warming of the Eurasian continent."
"Significant warming to the west of Mongolia tends to weaken the north–south temperature gradient and the atmospheric baroclinicity to its south and eventually can lead to weakening of the midlatitude cyclone activity over East Asia."
from Climate Change Skeptic Blogs via hj on Inoreader https://ift.tt/2GPjhCj
No comments:
Post a Comment