It is a common belief that extreme weather and climate events increased in frequency and intensity over the last century or half a century, a time period that saw a rapid global climate warming. However, our works show a more complicated and diverse change in China during the periods since 1950s or 1960s, with some (e.g. high temperatures/hot waves and short-duration intense precipitation) having an increased trend, some (e.g. typhoons and rainstorms) exhibiting no significant change, and others (e.g. low temperatures/cold surges, dust storms and mesoscale convection weather) having a decreased trend.
What are your observations and thoughts with regard to this issue?
It is accepted that, under human-caused climate change, some extreme weather events have increased, some have not changed, and some have decreased. I summarise some at https://www.linkedin.com/pulse/climate-change-weather-disasters-ilan-kelman
Thanks Ilan for your answer. But I could not download the paper. Would you please send it to me via email ([email protected]).
I have also summarized changes in major extreme weather events over China in two paper (Ren, G.Y., Chen Y., Zou X.K., et al., 2011, change in climatic extremes over mainland China based on an integrated extreme climate index, Climatic Research, 50 (1-2) 2011, 113-124. doi: 10.3354/cr01023, and Ren, G.Y., Guan, Z.Y., Shao, X.M., et al., 2011, change in climatic extremes over mainland China, Climatic Research, 50 (1-2) 2011, 105-111. doi: 10.3354/cr01067).
We recently found that mesoscale convection weathers, including thunderstorm, lightning and tornado days, all experienced a highly significant decline over China during the periods from 1960 to around 2012 (Xue, Xiaoying, Guoyu Ren, Xiangde Xu, et al., 2021. the trends of warm-season thunderstorm and lightning days in China and the influence of environmental factors. Journal of Geophysical Research-Atmospheres, 126, https://doi.org/10.1029/2021JD034950, and Xiaoying Xue, Guoyu Ren, Xiangde Xu, et al., 2023, spatial-temporal characteristics of tornadoes in China based on observational data of meteorological stations. Climate Research, 91: 83-96. DOI: 10.3354/cr01725).
The average increase in the global atmospheric temperature (called global warming) does not drive the dynamics of the atmosphere and oceans, i.e. the power of extreme weather events. Such dynamics are caused by gradients, or the differences over the distances in thermodynamic variables such as local temperatures, local pressures, etc., rather than the temperature values themselves (let alone global temperature averages that cannot be measured but can only be calculated from the local values using one or another method). If all the temperatures over the globe are higher or lower this does not result in higher gradients which are the true drivers of the global weather events.
Therefore, any change in the observed frequency of extreme weather events (be it real or just statistical fluctuations) has nothing to do with global warming.
Thank you Alexander.
Yes, the atmospheric and oceanic dynamics are important, and they are caused by large-scale temperature or air pressure gradients. The temperature or air pressure gradients in surface and upper air, however, have been believed to have a possibility to change in responding to the anthropogenic global warming, causing a change in atmospheric and oceanic dynamics which will lead to a change in extreme weathers and climate. The multi-decade variability in temperature and the aerosol climate-effect may further complicate the influence of climate warming on long-term change in extreme weathers and climate.
Guoyu Ren You said, "The temperature or air pressure gradients in surface and upper air, however, have been believed to have a possibility to change in responding to the anthropogenic global warming,.."
1st, beliefs are used in religion, they are not scientific arguments. It is not enough for someone to believe in something, arguments based on laws of physics are required.
2nd, the change of physical variables (gradients) does not differentiate between 'anthropogenic' or 'non-anthropogenic' warming.
And finally, global warming (if it is really global at all) includes, by definition, the average warming over the globe including, say, the poles, the equatorial regions, etc. Do you really think that a tornado's power over the local mainland China depends on little temperature change, say, in the South Pole or equatorial desert which are all the components of global warming?
Hi Alexander, I agree with you when you said "beliefs are used in religion, they are not scientific arguments. It is not enough for someone to believe in something, arguments based on laws of physics are required." I was not saying “belief”. “Believe” is synonymous with “think”. The wording may be inaccurate. I am not a native English speaker, anyway, perhaps "thought" should be used here. However, there are indeed researchers (not necessarily me) who tried to relate the observed change (increase in someone’s opinion) in extreme weathers to global warming (dominantly caused by human activity in mainstream scholars' opinion).
I do not think that the observed decrease in tornado frequency over China mainland had a linkage to large-scale surface temperature change or global warming. It was more likely related to the global or regional dimming which led to a weakening of regional surface heating due to the aerosols radiative effect, or the multi-decade variability of atmospheric and oceanic circulation modes. We made a brief discussion on the possible causes in our paper.
Under "extreme weather events" we can include our own "dramatic increase in humidity".
Our area used to be a dry area, especially in winter. In the last 5 years I have documented the dramatic increase of humidity from about 30% to the current 70%+.
I learned from another professor who was here in the 1970's and 1980's that they tried to promote this area as "cold but dry". This description was proposed to decorate automobile licence plates, but eventually it was not added on to the licence plates.
In any case, this phenomenon has brought this area to become so humid that it is normally covered with low-lying "clouds" (I can them "humidity clouds"), sometimes you can barely see the sun behind them. It used to be dry and cloudless.
Thank you Michael for your comments. That is an interesting phenomenon. Are you talking about Brandon, Canada? The increase in humidity over the last 5 years can be caused by what climatologists call inter-annual to decadal climate variability, which is different from "climate change". Climate change occurs in a time period of at least three decades, which may can be caused by both self-oscillations and extra-drivers of the climate system.
Dear Guoyu Ren
Yes, this is from Brandon, Manitoba in Central Canada.
While discussing weather events with other colleagues it was pointed out that the increase in humidity (a greenhouse gas) causes an increase in air temperature.
This winter ( as well as several years ago), it has been very mild. It is the only subject of discussion in this area. Where is the extreme cold temperatures, the piles of snow, etc?
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