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We recently held a live webinar bringing together experts to answer your questions about climate science.

There were so many fantastic questions asked in the webinar that we didn’t get time to answer them all. But we’ve been working hard behind the scenes to compile answers here on our blog:

Are projected tide depths available given the result of sea levels increasing? Already there are parts of Sydney that flood with a king tide – even without a storm.

Climate Change in Australia provides “sea level allowances” which indicate how much higher sea level extremes (including king tides) will be in future.
I’ve also done some work on this that is more explicit about the impacts – see this paper on Sydney.

Answer provided by Ben Hague, Bureau of Meteorology.

Sea level rise will lead to higher annual peak water levels, commonly known as King Tides. In certain locations, the King Tide reaches higher levels in some years compared to others. These tides follow natural cycles of 4.4 and 18.6 years, driven by the moon’s orbit. Research from hub project, Extreme climate: dry, wet, hot-and-dry, has also identified links between water level variations and ENSO (El Niño-Southern Oscillation), which have been shown to influence mangrove dieback. A current hub project, Oceans and Coasts: connecting climate variability and extremes across scales, is developing advanced models to improve the prediction of future King Tides and more infrequent annual exceedance probability water levels, aiding adaptation planning over the coming years and decades.

Answer provided by Julian O’Grady, CSIRO.

Are we in a period of accelerated heating? Is there evidence that there could be a step change in the rate of warming?

Global average temperature is increasing at an accelerating rate. For example, the rate of increase ‘now’ (over the past 3 decades) is higher than it was in the middle of the 20^th Century. This is expected and consistent with climate projections. This acceleration will continue until the net effect of the factors that ‘force’ the temperature change – greenhouse gas increases and aerosol reductions – flattens out.

Regional (as opposed to global) warming is also accelerating in many regions, including Australia.

 

The plot above (adapted from IPCC 2021) shows projected change in global mean temperature over the 20-21st century relative to 1850-1990 under three different scenarios of greenhouse gas emissions (Shared Socioeconomic Pathways or SSPs). This plot shows only the median value for simplicity (there is a range of possibilities around this). The horizontal lines at the bottom show how long the period of acceleration is expected to last for each emissions scenario – under the fossil-fuel intensive SSP3-7.0, the rate of global temperature increase continues to accelerate beyond the end of the century.

Also, global average temperature, and in many areas of land and ocean have been unusually warm in 2023 and 2024 so far, raising questions about whether we are seeing a step change or unexpected acceleration in warming. Understanding the reasons for recent dramatic increases and whether this is evidence of faster-than-expected warming – and exploring the possibility of a step change – is the subject of ongoing research.

Answer provided by John Clarke and Michael Grose, CSIRO.

How often are CMIP updated? Can risk assessment reviews align with CMIP updates? And do the climate models from state governments update to align with CMIP? 

The Coupled Model Intercomparison Project (CMIP) modelling is updated on roughly a 7-year cycle. The modelling is completed in time to allow the international research community to assess the model results and publish their results in time for the Intergovernmental Panel on Climate Change (IPCC) to consider them for the next IPCC Assessment Report. However, once the data are available, the results must be assessed at the national scale and then combined with other lines of evidence to produce meaningful climate projections. This takes time and money.

Not all states undertake their own modelling (regional climate modelling) but those that do often try to update their results once a new CMIP is available.

Answer provided by John Clarke, CSIRO.

It is worth noting that new CMIP outputs tend not to shift projection numbers in a significant way. They are experiments and offer a ‘plausible’ estimation of future change in the climate. They add to our evidence base rather than replacing it. So, it is unnecessary to update risk assessments with new numbers each time a new set of experiments are completed. It is advisable to revisit your risk assessment and adaptation plans/actions regularly. This might be at set intervals (eg every 3 years) or as new information becomes clear or other changes occur, for example, increased damage from weather events or more information about an animal species of concern.

Answer provided by Sarah Boulter, University of Tasmania (NESP Climate Adaptation Initiative lead).

Temperature vs Excess Heat Factor (EHF): which one do you think is easier to use as an indicator of heatwaves for comparing?

If you are using pure temperature you need to define a threshold for a heatwave, e.g. a number of consecutive days above 35 degrees Celsius. This threshold may be based on your risk assessment, which sets out the risks to be managed for a certain asset (for example infrastructure). If you use Excess Heat Factor (EHF), the heatwave depends on the average climate for the location. This is a much better approach when you’re considering impacts on people as it accounts for residents being adapted to the local environment.

Answer provided by David Hoffmann, Bureau of Meteorology.

Where do we access Australian projections for the low likelihood, high impact events and/or hot models?

Low likelihood high impact (sometimes now reworded as High Impact Low Likelihood or HILL) outcomes or events include warming at the upper end of what is possible, resulting in a very hot world; sea level rise at the upper extreme end of possibilities due to rapid collapse of Antarctic and Greenland ice shelves and ice sheet; the crossing of climate tipping points resulting in rapid and irreversible change; and severe compound extremes.

Similar to any type of risk, these events and outcomes can’t be ignored but should be kept in perspective – some are certainly unlikely, but for other it is unclear how likely they really are due to deep uncertainty in the processes behind them, and others in fact become likely if we experience high levels of warming (e.g., collapse of the Greenland ice sheet).

Nationally consistent data – including from a representative “hot model” – will be made available through the Australian Climate Service.  State projections also include projections from representative hot models (models at the upper end of what is considered plausible in terms of warming).

Answer provided by David Hoffmann, Bureau of Meteorology and Michael Grose, CSIRO.

Do you have any experience on the application of rating or ranking risks, beyond just the use of likelihood and consequence? Often we receive feedback from stakeholders that traditional risk models do not fit climate risk complexity.

We asked Drs David Rissik and Fahim Tonmoy (Deloitte) about their experience of complex risks:

“We have started developing and testing approaches to integrate complex risk into risk prioritisation. This does not replace our existing (traditional risk assessment) approaches but adds value. I think most people have recognised and incorporated complex risk in some way shape or form, but it has been quite ad hoc. We have noticed that many practitioners take stakeholders through the challenge of complex risk and many people talk to it, but it is not formalised into the assessment. Our approach does this. We hope to write something up on this as there is not a lot of guidance on the integration of complex risk in to risk prioritisation.”

Often organisations try to integrate risk matrices from climate adaptation standards with corporate risk matrices. Corporate risk matrices are often not set up to assess ‘rare catastrophic’ or ‘force majeure’ events. They focus on plausible events that fall within the daily/monthly/yearly operational experience and what the organisation has reasonable control over. Do you recommend establishing a separate risk assessment/prioritisation process for climate change risks rather than integrating them with standard corporate risk matrices, and do you have any examples of organisations who have done this?

Being able to add a line for the ‘low probability, catastrophic consequences’ in a corporate risk matrix would make sense. We should be having the conversations about what if these low probability (but still plausible) events happen – even if it doesn’t lead to action now. The law tends to observe that you can’t unknow what you know. So, if there is some information to say something is low probability but has catastrophic consequences, it is prudent to have the conversation. The law also recognises that the response must be reasonable, so the expectation that every risk will be fully addressed is not real.

Answer provided by Sarah Boulter, University of Tasmania (NESP Climate Adaptation Initiative lead).

We asked Dr David Rissik (Deloitte) who told us:

“We strongly recommend, and try our best, to work with existing enterprise risk frameworks as much as possible. The reason for this is that using existing and accepted corporate language enables easier alignment with other processes within the organisation. It also helps to link with their risk appetites and values and prevents the need for more detailed work to be done in that space which can save them resources. That said, we generally do adapt some of the criteria to make them more realistic to climate change challenges. Things like economic impacts etc which have numbers associated with them can be pretty meaningless when looking into the distant future. The issue around low likelihood/high impact events can be brought into the framework and discussion quite easily. In short, we do develop new risk matrices to make them fit for purpose, but we don’t reinvent wheels.”

On managing climate risks that are ‘rare catastrophic’ or ‘force majeure’, Dr Fahim Tonmoy (Deloitte) added:

“It often depends on the risk appetite of the organisation. If the organisation is managing long lasting critical assets like ports, airports, dams, or hospitals then engineering design of new infrastructure requires us to consider the wider envelope of risks including the low likelihood but high consequence events. However, when you are moving from that engineering design space to understanding such risks within the operation or supply chain, then it starts to get blurry and largely depends on the risk appetite of the organisation…often existing risk frameworks are not suitable to longer-term strategic risk framing, but they can be tailored to bring that strategic thinking. That tailoring process also help to develop internal climate risk literacy within an agency.”

Should you do a vulnerability assessment before a risk assessment?

Assessing vulnerability is part of assessing climate risk, along with understanding hazard and exposure to them. Assessing vulnerability needs to be done before rating risk. Most climate risk assessment integrate vulnerability assessment in the risk assessment approach. Vulnerability assessments can also be done as a standalone process to consider vulnerability based on exposure to climate hazards, sensitivity of community, asset or system of interest and the adaptative capacity of those people, assets or systems.  To rate risk vulnerability can be brought together with likelihood and consequences of hazards.

Answer provided by Sarah Boulter, University of Tasmania (NESP Climate Adaptation Initiative lead).

The fine scale models we have been using in our scenario planning processes have been based on RCPs (Representative Concentration Pathways). What effect will the adoption of the SSP (Shared Socio-economic Pathways) scenarios have and are there plans to build fine-scale models based on SSPs? 

Queensland, New South Wales, CSIRO and the Bureau of Meteorology have been working on high resolution downscaling based on SSPs. NSW has recently released their 4km resolution, SSP-based climate projections, known as NARCliM2.0. The downscaled modelling from the rest of these groups will be available soon. However, it is not a given that your scenario planning should be updated. This decision should be based on your needs (what you’re planning for and your risk appetite). For example, if it’s vital to understand the impacts of the hottest plausible future, you should consider looking at results from the CMIP6 so called ‘hot models’ (keeping in mind that these are considered low likelihood).

Answer provided by John Clarke, CSIRO.

When you look at the Bureau of Meteorology website for the radar sites, there are a limited number of radars. Should there be more radar sites to cover the area of Australia comprehensively, and is this a problem in providing long term climate data about an area not covered by radar?

The limited coverage by ground-based radar in Australia primarily reflects the cost of building and maintaining these systems. In more remote areas, satellite data can provide supplementary information on the coverage and intensity of precipitation, although its estimates tend to be lower resolution (both spatially and temporally), and less accurate than those from ground-based radars.

In theory radars can be used as a source of long-term climate data and increasingly they are. However, radars have a limited period of record and limited coverage. Using them for climate data has only become possible quite recently – many countries have only had national radar networks since the late 90s or early 2000s, so for a long time the records simply weren’t long enough to say anything meaningful about the climate. Another issue with radars is that changes in hardware, data processing, and archival practice (e.g., the resolution at which data are stored) can lead to discontinuities in the record that may mask long-term changes in precipitation frequency, intensity or distribution.

There is a data set under development at the Bureau (with Melbourne Uni) of hourly rainfall, which is intended to blend gauge, satellite and radar data, although this will not be an especially long-term data set (back to 2008 or thereabouts) and it is not designed explicitly for long-term observations (its main purpose is to support flood forecasting although there are other applications too).

One significant potential climate application of radar data is in quality control of gauge data (rainfall gauge) in areas with radar coverage, in particular detecting gauges with false low/zero readings (as might arise, for example, from a gauge blockage). The Bureau already uses radar data for this purpose in its operational quality control but, as I understand it, only for follow-up investigations of data already flagged by other checks, not as a primary quality control tool.

Answer provided by Blair Trewin and Rob Warren of the Bureau of Meteorology.

Are there any great models or ideas on how to track progress on managing climate risk? Or reducing vulnerability? Adapting? Building resilience? How does the way of framing it influence what can be measured/monitored? 

My quick answer is that no, it is not easy and there is no good formula, but the more you understand good evaluation practices the easier it is to know how to approach such monitoring and evaluation of adaptation / risk / vulnerability.

Answer provided by Sarah Boulter, University of Tasmania (NESP Climate Adaptation Initiative lead).

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