Setting the Record Straight with the BOM

During the recent Senate Estimates Session with the Bureau of Meteorology (BOM), I tabled a graph from the United Nations Intergovernmental Panel on Climate Change (IPCC) report to challenge some of the exaggerated claims we’ve been hearing about extreme weather events such as cyclones, floods, and fires.

For years the BOM has always referred me to the IPCC’s work as the authoritative source on climate science. I specifically pointed to the IPCC’s Assessment Report 6, chapter 12, where they provide an analysis of a wide range of weather events. What struck me—and I think it should strike everyone—is that for nearly every major type of extreme weather event, the IPCC finds that there has been no detectable change in frequency or severity over time. This includes river floods, fire weather, tropical cyclones, and coastal floods. The data doesn’t support the claims that these events are becoming more frequent or intense because of “climate change”.

This is important because politicians and the media have often linked these events to human-induced climate change. They claim that floods, fires, and cyclones are somehow the direct result of our carbon dioxide production.

Yet if the IPCC itself, the body these same politicians refer to, says there’s no significant change in these events, why aren’t we calling out this misinformation? Why isn’t BOM calling out this misinformation?

For example, tropical cyclones – the IPCC indicates no change in their frequency or severity, not just for today, but looking ahead through to 2100—even under the worst-case climate scenario. And yet, we continue to hear false claims that “human-induced climate change” is worsening cyclone events. This isn’t true. These events have been part of the natural weather cycle for millennia.

The BOM Director, Dr Johnson’s response acknowledged that the science on cyclones is evolving and confirmed that while there may be fewer cyclones in the future, the ones that do occur may be more intense. Yet again, these claims are based on unsubstantiated projections—not hard data. They’re misinformation!

What’s more, looking at the IPCC’s tables, which break down the evidence of (naturally) varying weather patterns, for nearly every phenomenon—whether it’s precipitation, floods, fire weather, or tropical cyclones—the data simply doesn’t support the idea of dramatic increases due to “human-induced” climate change.

So, why are we still seeing politicians and the media push these claims?

This is not saying to ignore the importance of understanding climate variability, it’s about dealing with the facts – the measured data. The science must guide us, not the political agenda. And if the observed, measured scientific data says these extreme weather events aren’t changing as some claim, we need to stand firm against the misinformation.

Let’s be clear: the data doesn’t support the alarmist rhetoric. We should be calling out the misinformation and ensuring that decisions, policies, regulations and public opinion are based on what the science actually tells us—not on what some want us to believe.

I will continue to hold taxpayer funded agencies and politicians accountable. The truth matters, because, as always, it’s we the people who pay.

Transcript

Senator ROBERTS: I’d like to table this graph from a United Nations Intergovernmental Panel on Climate Change report as the basis for some brief questions. I don’t have too many questions today. I’ll start with a little preamble just to set the scene for this. When you get the graph, you’ll see it. I refer to misinformation being put out that cyclones and floods are getting more frequent and severe. Over many years in this committee the BOM has referred me to the United Nations Intergovernmental Panel on Climate Change. This might surprise you, but I’m not actually going to argue with you on the merits of the IPCC today, even though they’re a bunch of net zero pushers and are politically driven. I’m going to quote them, because you claim they’re the authority. I’ll take you to Assessment Report 6, chapter 12, table 12.12, by working group 1, on the science of climate, at page 1856. In that table is just about every type of measurable weather event. Some call it extreme weather events.

The blank or white boxes indicate there is no detectable change in frequency or severity of the weather event. I’ll go down the list of what the IPCC itself says—not me. River flood—no change is detected in current period. No change is expected to be detected under the worst case climate scenario by 2050 or even by 2100. Fire weather—no change is detected in current period or expected in the next 75 years. Tropical cyclone—no change is detected in current period or expected in the next 75 years. Coastal flood—no change is detected in current period or expected in the next 75 years. Pluvial—there’s a minor risk in the most extreme, worst-case scenario. If your net zero gods at the IPCC say the data shows weather events are not getting worse because of climate change, why isn’t the Bureau of Meteorology calling out the misinformation peddled by politicians when they state that this flood is because of climate change, this fire is because of climate change or this cyclone is because of climate change? Everyone knows that’s not true. These events have been happening for millennia. Even the scientists in the United Nations that you reference say it’s not so.  

Dr Johnson: I might make a couple of preliminary remarks and then ask Dr Braganza, who is online, to join in. I haven’t had a chance to study the page that you’ve just supplied me. I think many times I’ve referred you to the State of the climate report that the bureau produces with the CSIRO every two years, which contains the latest up-to-date information on climate.  

Senator ROBERTS: I’ve read each of them.  

Dr Johnson: I know you read it, and I’d encourage you to refer to it again. Across a range of phenomena we know there are very strong signals already from climate change, in particular around temperature and in particular around drying in the southern, south-east and south-west parts of Australia. Those signals are very strong. The level of confidence in them is very high. Some of the signals for other phenomena, including tropical cyclones, are still evolving and maturing. We have seen an increase in the incidence of high-intensity rainfall. We know as a matter of fact that, as the atmosphere warms, it holds more moisture—probably up to 10 or 11 per cent more—than it would otherwise have, and that we’ve seen an increase in high-intensity events. We’ve certainly been on record saying that we expect in Australia it’s likely that there will be a lower number and frequency of cyclones, but they’re likely to be more severe. We’ve been on the record for that for ages. We’ve also been on the record on many occasions—  

Senator ROBERTS: Could you explain the basis for that? The UN says it’s not—  

Dr Johnson: I’ll come to that. Dr Braganza might want to say something about this in a minute. We’ve also been on the record that, particularly when it comes to individual cyclones and individual rainfall events, it’s very difficult to attribute single events to climate change. We’re talking about longer term global trends here. That’s been our position for some time, and it remains so unless new evidence is entered into existence that would cause us to change our mind. I can only be accountable for the science we do. I can’t be accountable for how those in the public domain choose to talk about it. We certainly provide advice, as we’ve done to this committee many times and in many other fora, about what we’re observing and what our science is telling us is likely to come down the pipeline, and also where we have higher or lower confidence about what is or isn’t coming. They would be my general comments.  

Senator ROBERTS: Did I hear you correctly—just before we go to Dr Braganza—that cyclones are not becoming more intense?  

Dr Johnson: No, I didn’t say that. I said that in our outlooks we think there’s a reasonable likelihood—Dr Braganza will be able to quantify this in more specific detail—that the Australian region is likely to see fewer cyclones, but there’s a likelihood that they’ll be more intense rather than less intense. Dr Braganza is our lead in this space and I’d rather he answer these detailed questions that you might have.  

Dr Braganza: For tropical cyclones, the bureau, as Dr Johnson has pointed out, has consistently communicated that we have potentially seen a reduction in the number of tropical cyclones in our region, in particular in the east. We haven’t communicated that we’ve seen any significant change in intensity. Categorising changes in tropical cyclones is difficult. We’re limited to the satellite era. Prior to the satellite era, categorising tropical cyclones for severity and even whether or not they’re a tropical cyclone in the mid latitudes becomes difficult. There are data limitations in trends in tropical cyclones. The bureau has been entirely consistent in how it’s described those and entirely transparent in the data limitations. We have not communicated that we have seen large changes in tropical cyclones that are due to climate change. We don’t communicate around these individual weather events that they were caused by climate change. For tropical cyclones there are multiple aspects to the weather event. When we talk about intensity, we’re often talking about wind speed. Wind speed is just one aspect of a tropical cyclone. There’s also rainfall intensity and there’s storm surge intensity. Due to sea level rise and increased warmth in the atmosphere, we expect increased heavy rainfall and increased storm surge activity from all such events, not just tropical cyclones. There are also events such as east coast lows and others. Observational data is what it is.  

Senator ROBERTS: I don’t expect you to comment on this, because you don’t have the table in front of you, but I’ll just go through chapter 12 and table 12.12, emergence of climate impact drivers in different time periods. That’s with regard to the future. The white colour indicates that there’s no confidence in what they’re saying or what they’re projecting. In terms of already emerged and ‘worst case scenario’ in the future by 2050 and by 2100: mean precipitation, no confidence in the data. No trend has emerged. River flood is the same. Heavy precipitation and pluvial flood is the same. Landslide is the same. Aridity is the same. Hydrological drought is the same. Agricultural and ecological drought is the same. Fire weather is the same. Tropical cyclones is the same. Coastal flood is the same. These are often taken advantage of by politicians and the news media; there’s no evidence for their comments attributing them to climate change caused by humans.  

Dr Braganza: I’ll have to take that on notice since I don’t have the material in front of me. Some of the phenomena you’ve called out again in terms of establishing observed trends is limited by sample size. You’re talking not about weather events necessarily; you’re talking about impact events such as the size of a flood following heavy rainfall. There are possibly data limitations involved, but I would have to see exactly the material that you’re referencing.