On Monday 25 May 2020 CSIRO’s experts on climate change science presented to Commissioners of the Royal Commission into National Natural Disaster Arrangements. The Royal Commission commenced hearings on this day to gather evidence about coordination, preparedness for, response to and recovery from disasters as well as improving resilience and adapting to changing climatic conditions and mitigating the impact of natural disasters.
Our CSIRO Climate Science Centre scientists, Dr Helen Cleugh and Dr Michael Grose, provided research and information on past, present and future climate and CSIRO’s climate science research relevant to understanding and responding to natural disasters.
Here are six of the top messages that Dr Cleugh and Dr Grose shared with Commissioners.
1. Timeframes are important
Weather is what we experience on a day-to-day basis. Our climate is the average weather conditions over many years. Our climate change research looks at climate trends over many years, describing how they have or will change as a result of external factors.
At the short timeframe, we can make predictions of the climate in coming months. In recent decades our understanding, observations and models have advanced such that scientists are able to provide seasonal predictions of the climate in the season ahead, say 1 to 3 months, and even up to 6 months.
At the other end of the timeframes, CSIRO have been providing longer-term climate simulations and regional climate projections for at least three decades which have been contributed to the IPCC climate assessments; informed national and global climate policies; and provided the information needed for adaptation planning. Modelling from the Australian Community Climate Earth System Simulator, or ACCESS, is an important contribution to the global effort.
2. Forecasting the climate over multi-years and decades is challenging
Bridging the gap between seasonal climate forecasts and longer-term climate change projections is one of climate science’s grandest challenges.
Researchers at CSIRO are tackling this challenge through our Decadal Forecasting Project, which brings together knowledge about the oceans, climate modelling and high-performance computing to produce new forecasts that bridge this gap and are applicable to people making decisions over this timeframe.
3. There are multiple future trajectories of our climate
Over the long term, the future of our climate depends on three factors; natural year-to-year and decade-to-decade climate variability, the concentration of greenhouse gases and aerosols in the atmosphere, and how the climate system responds.
On greenhouse gases – since we don’t know exactly what emissions will be in the coming decades or centuries climate scientists use a range of future scenarios of greenhouse gases to model future climate. The latest scenarios include socio-economic pathways into the future, like whether sustainability is a high priority, the world experiences significant regional rivalry or we follow a pathway with greater fossil fuel use.
4. Attributing climate change to an individual event is an emerging area of science
The study of understanding and quantifying climate trends and extreme events and identifying any link to climate change is called ‘attribution’. Attribution methods are well advanced for climate properties like temperature, but less so for some other extreme events.
Various techniques, including our modelling, shows clearly that increasing greenhouse gases are responsible for observed warming of Australia’s climate over the last 100 years, and especially since mid-20th Century. It is now clear that human activity has increased the intensity or frequency of hot events on land and in the ocean as well as some other types of climate extremes.
5. Climate change affects the processes that drive variability in the climate
Studies have shown that climate change has an impact on processes that drive the variability in our climate, like the El Nino Southern Oscillation (ENSO) and the Southern Annual Mode (SAM).
Therefore, the weather and climate that we experience – especially extreme weather and climate events – are also affected by the way climate variability is affected by climate change. There is an interaction between climate variability and climate change.
This means that it is very important to have high quality modelling capability in Australia, to provide future predictions and projections of future climates; because the past is no longer a reliable guide to the future, because of climate change.
6. Climate change projections indicate increased risks of climate extremes and natural disasters
There is high confidence that Australia will continue to warm. 2019, Australia’s warmest year on record, would become a cool year in the future under high greenhouse gas emissions.
Hot days above 35°C are projected to increase in many of our major Australian cities. This could have substantial impacts on our health, workforce productivity, energy demand and infrastructure.
There is an observed long-term drying trend in much of southern Australia. This drying trend is projected to continue, although there will be continuing large natural variability.
The combination of extreme heat and lower rainfall contribute to an increased risk of dangerous fire weather days. More dangerous weather conditions for bushfires are likely to occur due to climate change.
In terms of drought in southern Australia, climate change projections suggest that time in drought and intensity of drought are likely to increase in the future, and that the impacts of droughts will be greater as they will be hotter.
Rainfall events that we experience in the future are likely to be more intense. This increases the risk of flash flooding in the future, especially in small or urbanised catchments, which could lead to increased erosion.
Sea levels have risen, which is also projected to increase around Australia in the future, which poses further threats to coastal communities.
A future decrease in the total number of tropical cyclones is projected, but the proportion of intense cyclones is likely to increase.
Visit Climate Change in Australia for the most recent set of comprehensive climate change projections for Australia.
Review the presentation
Remember, as with all presentations to the Royal Commission on National Natural Disaster Arrangements, our climate scientists’ presentation can be viewed here and you can access past recordings from the Commission's live stream site here (follow instructions to past recordings).
CSIRO’s contribution is accessible by searching for Part 2 on day 1 of the Royal Commission.