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Human-induced warming has driven increasing precipitation variability
Anthropogenic climate warming has led to increased precipitation variability over much of the globe, according to a new study, which points to several hotspots for this trend. This effect is particularly prominent over Europe, Australia, and eastern North America, say the study’s authors, and is largely driven by increasing atmospheric moistening and decadal-scale changes in atmospheric circulation. As the climate warms, the atmosphere becomes more capable of holding moisture, leading to greater fluctuations between extreme precipitation events and wider swings between wet and dry episodes. Such amplified precipitation variability can profoundly impact human society and ecosystems, posing challenges for weather and climate forecasting as well as for adaptation and resilience planning. Although many global climate models project increasing precipitation variability – especially in wet regions – due to higher atmospheric moisture and weakened large-scale atmospheric circulation, the phenomenon is far easier to predict than to observe. As a result, it remains unclear whether increased precipitation variability has already emerged in observations. To address these uncertainties, Wenxia Zhang and colleagues leveraged five global-scale and eight regional-scale datasets of daily precipitation observations, which spanned 1900 to 2020. Zhang et al. report that precipitation variability has systematically amplified over the past century across various timescales and regions, driven primarily by increased atmospheric moisture from anthropogenic warming. According to the findings, roughly 75% of land area has experienced an amplification of precipitation variability, with daily variability increased by 1.2% per decade globally. The authors note these precipitation swings pose “threats to the climate resilience of infrastructures, risk management, agriculture, ecosystem functions, and economic development.”
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Professor Steven Sherwood is ARC Laureate Fellow at the ARC Centre for Climate System Science and UNSW Climate Change Research Centre and Chief Investigator at the ARC Centre of Excellence for 21st Century Weather
This paper shows something that is consistent with expectations and previous results but simpler and clearer: rainfall is becoming more variable around the world due to global warming.
Past studies of the observational record either focused on average rain, which is not systematically changing globally; or rainfall extremes, where changes are hard to measure accurately. This study just looks broadly at the variability, a handy and simple measure.
As expected, it has increased in most places, including Australia, which means rainier rainy periods and drier dry periods. This is going to increase as global warming continues, enhancing the chances of droughts and/or floods.
Milton Speer is a Visiting Fellow in the School of Mathematical and Physical Sciences at the University of Technology Sydney
I strongly agree that Anthropogenic climate warming has led to increased precipitation variability over much of the globe and agree that there are several hotspots for this trend.
The authors state that the effect is particularly prominent over Europe, Australia, and eastern North America and is largely driven by increasing atmospheric moistening and decadal-scale changes in atmospheric circulation.
In fact, for a large part of southeast Australia, increasing variability is precisely what has happened in relation to precipitation as global warming increases [10.3390/CLI12050075; 10.3390/CLI12040049; 10.3390/CLI11040076; 10.3390/W14193073; 10.3390/CLI10060084;] You can include also Perth representing southwest Australia [10.1016/j.procs.2020.02.244].
In addition to Europe, Australia and eastern North America, it has occurred in southwestern North America [10.1016/j.procs.2015.09.181], and Cape Town, South Africa [10.1016/j.procs.2018.10.323].
Although the paper’s findings are significant, similar conclusions have been reached in recent years that are described within the papers listed above.
Dr Tom Beer is the Director of Safe System Solutions Pty Ltd. He is a Past President (2007-2011) of the International Union of Geodesy and Geophysics, and retired Program Leader of CSIRO Climate Change and Variability
It is well known theoretically and experimentally that warm air can hold more water vapour than cold air. If the atmosphere as a whole heats up, due to climate change, global warming or due to some other cause then it will hold more water vapour which means that there is more water available for rainfall.
This paper has, firstly, used a global daily precipitation data set to show that the variability in daily precipitation has indeed been increasing. Almost. Despite the abstract claiming that this is “particularly prominent over Europe, Australia and eastern North America”, Figure 2 shows that it is NOT the case for Australia. I live in Australia, and it is the Australian data that interests me, and the paper is not showing what the abstract claims to be showing.
The authors have the good grace to 'note that the signal is weak over Australia for the shorter period of 1950-2020 because of large internal variability'. Maybe. Maybe not. Australia is not really the focus of the authors’ thoughts. They spend a large amount of effort trying to determine what the cause of the increased variability might be and conclude that it is greenhouse gases rather than aerosols or dynamic variability. This effort was done using climate models.
