Australian Rural & Regional News asked a few further questions of Frank and Michael, answered below the article.
Frank Batini and Michael Freeman
We are convinced that the reports of rainfall change in the southwest region of Western Australia being linked to increased levels of carbon dioxide in the atmosphere are not correct. We believe this despite all the media reports, climate change modelling, Government documents and peer-reviewed research papers from Universities that say the opposite. We feel very lonely.
We acknowledge that carbon dioxide (CO2) is one of the greenhouse gases, with water vapour the dominant gas. Without greenhouse gases our Earth would be inhospitably cold and humans could not have evolved. In addition, we note that CO2 is not a pollutant, it is a key ingredient for photosynthesis. Without photosynthesis humans would die.
Climate projections by the West Australian Department of Water (DWER, 2021) state that the southwest has experienced a marked drying trend since 1970 and that this is linked to rising levels of CO2 and temperature. Rainfall models show that further decreases in rainfall are likely, up to 15 per cent by 2030, and a further 25 to 45 per cent by 2090, depending on whether intermediate or high emission scenarios for carbon dioxide are used.
The observed reductions in rainfall are said to be larger than recorded anywhere else in Australia. For this reason, the southwest region has been likened to the “canary in the coal-mine” and has been selected for special attention. The Government has recently funded a $3 million Climate Change Initiative study, based on refining the modelling of future climates.
The choice of a baseline is critical, since an inappropriate selection could lead to incorrect conclusions.
We have serious concerns about the choice of a baseline for modelling that starts in 1950, after several decades of above-average rainfall. If we use this baseline for modelling climate change, temperature and carbon dioxide levels have risen and rainfall has fallen. The reduction in rainfall may then be attributed to climate change. A baseline of between 1950 and 1970 has been accepted without question in several research papers and reports published by academics, CSIRO and Government. These data are then used to measure and report change, as well as for scoping future climate scenarios.
When studying climate change and rainfall trends, we believe that the longest records available should be used. If we look at records for Perth from 1880 (Department of Water 2008, Report HG14, Fig 1), the data no longer support the conclusion that rainfall and carbon dioxide are linked. The average rainfall in late the 19th century was comparable to that of the present.
Similar results were obtained from Bureau of Meteorology (BOM) data for Jarrahdale, a small town located in the Darling range, some 50 km southeast of Perth (Fig 2). Rainfall at Jarrahdale 1882 to 1910 averaged 1118 mm and from 1975 to 2017 it was 1064 mm. During this period of 132 years, CO2 levels rose by about 30 percent, with little correlation to rainfall.
In addition:
- between 1915 and 1965, as carbon dioxide levels were rising, rainfall in Jarrahdale and Perth increased.
Tree ring studies by the University of WA (UWA) at lake Deborah near Southern Cross, dating back to 1350 CE (O’Donnell et al 2021) show cyclical patterns of wetter and drier periods for southwest of WA that continue for several decades, and have been independent on the level of carbon dioxide in the atmosphere. The recent decline in rainfall is not unusual in terms of either magnitude or duration. The authors conclude that the twentieth century was the wettest of the last 700 years, despite major increases in greenhouse gas emissions.
When these issues were raised recently at a seminar on Climate Modelling held at Murdoch University, the response was
1) 1950 was selected to comply with an International Convention on climate modelling; and
2) pre 1950 data have not been “peer reviewed” and may be inaccurate.
However the rainfall data quoted in this article come from government agencies and a respected university. The data don’t fit the modelled results.
We have also written to the WA Minister for Climate Change but the response received failed to address our substantive concerns.
We conclude that studies of tree rings as well as long-term rainfall data from two stations do not support the hypothesis that increases in carbon dioxide levels lead to significant reductions in rainfall in southwest of WA. Given these serious anomalies, how credible will any climate modelling results be?
Frank Batini is a forester and consultant in NRM. Michael Freeman is a geologist.
Questions from Australian Rural & Regional News
ARR.News: You say you “are convinced that the reports of rainfall change in the southwest region of Western Australia being linked to increased levels of carbon dioxide in the atmosphere are not correct.”
Assuming the pre 1950 data you have provided is correct, isn’t it rather that it is just too soon to tell? ie You cannot – yet – categorically conclude that there is no connection?
Frank Batini: The data comes from BOM, we need to expect that it is correct. We have analysed 140 years of data from 1880 to 2020. These are the best records available. Surely 140 years should be ample. What these data show (that the modellers using 1950 as a base, miss) is that rainfall is cyclical, not only one-directional (eg down). The cycles are long and if you only use more recent data, you do not see the overall trend. UWA data support this.
ARR.News: Waiting until the data is conclusive one way or the other could well be too late to do anything about it, wouldn’t it?
Frank Batini: Agree.
ARR.News: What is the outcome you are seeking from a consideration of pre 1950 data?
Frank Batini: I am seeking a more scientific approach to climate change modelling. A model that can explain all of the variations we see, not only some. A model that is reliable.
ARR.News: Has any lag time between increased CO2 levels and weather trends been allowed for or considered in either the climate modelling you are challenging or your own reasoning?
Frank Batini: Unsure about the modelling as it is a “black box”. Only the modellers understand all the data inputs and assumptions made. All we the public/ Ministers see is a result/statement or a map and we have no real way of knowing how this was derived or how accurate this may be. In our case, I think 140 years would allow for any time lag.
ARR.News: What do you consider to be the factors affecting rainfall in south west WA?
Frank Batini: I am not a climatologist. The south west is affected by a series of cyclone/anticyclone systems we see every night on TV. During the winter, as the monsoons move towards India, these systems are dragged north and begin to cover the south west. The movement north may also be affected by the warm Leewen current and other interactions in the Indian ocean similar to El Nino/La Nina in the Pacific.
ARR.News: What do you believe could be the broader risks of oversimplifying a rainfall – CO2 link in south west WA? For instance, is it possible that there are other causes and effects and related countermeasures that might be overlooked? Or a risk of damage from acting on the assumed link?
Frank Batini: If we oversimplify the problem we may rush into the wrong solution, or too fast.
As an example, the fire chiefs tell us that we need to reduce CO2 ASAP to better control wildfire. This provides an excuse for their past efforts but ignores relevant questions. Will reducing CO2 levels reduce global temperatures? (Maybe). In what time frame?(Decades?) Has temperature a great effect on wildfire behaviour ? (No). This then may distract us from the task of mitigating the potential impacts of wildfire by acting NOW on the many positive things we can do.
ARR.News: Do you know of any scholarly research into climate change causes and effects that is looking more closely into links between CO2 and rainfall, increased or decreased, in WA or other parts of the world or under different conditions?
Frank Batini: No, I have not investigated this.
CO2 may be acting on another factor (that we have not yet recognised) which then affects rainfall.
I think the key in our story is the rainfall/CO2 graph for Jarrahdale. 140 years of data, 30 per cent increase in CO2, no change in rainfall overall, BUT decadal cycles of wet/dry. This is supported by the UWA data. Also of significance is that when CO2 levels were highest (20th Century) the rainfall was also highest (UWA). I think any climate modeller would need to explain these apparent inconsistencies.
