December 12, 2020 | Published by |

The past four months have seen the Heatwaves and Cold Air Outbreaks research program focus very much on improving our capacity to understand and help others in research and industry get an insight into the impact of extreme heat events.

Detecting and attributing a climate component to extreme heatwave events has become an important area of study over the past decade, particularly in communicating the immediacy of climate change impacts in a way that communities understand. However, recently there has been considerable discussion within the climate science community about the reliability of these attribution studies. To overcome this, CLEX researchers joined a team of international researchers to compile a detailed detection and attribution protocol for future analyses. In addition to building a consistent, robust attribution framework for future researchers to follow, they also produced a plan for communicating these results to the public. The upshot is a foundational process that acts as a reliable framework, highlights potential pitfalls to be avoided, and puts in place a consistent process that can now be used by attribution researchers worldwide.

Another international collaboration looked at the burning embers diagrams used in International Governmental Panel for Climate Change (IPCC) reports. The burning embers diagrams aim to produce a consistent set of figures that indicate when climate impacts will be felt as global temperatures reach identified temperature thresholds. While the review focused on the clarity of these figures and producing a consistent structure for the expert elicitation process that informs these impact diagrams, the standardised comparison used by the researchers also produced a separate, unexpected result. The researchers found that as science improved across the IPCC reports a clear trend appeared showing that major impacts such as heatwaves, the collapse of the West Antarctic ice sheet and coral bleaching became more likely to occur at lower temperatures than originally estimated. So, while the review produced new protocols to improve these impact diagrams it also added further emphasis to the need to take urgent action to prevent the worst impacts of global warming.

One of those impacts has been the rise in marine heatwaves. In yet another international collaboration, researchers from the Heatwaves and Cold Air Outbreaks program and the Variability and Teleconnections program came together to identify the worst marine heatwaves and then reveal the key processes that triggered them and led to their demise. They found that these record-breaking heatwaves tended to occur in summer but, surprisingly, before the annual peak for warmest ocean temperatures had occurred and were most often associated with El Niño events. The key factor that formed these marine heatwaves was a lack of wind and clear skies usually caused by persistent high-pressure systems. These stalled systems prevented ocean mixing keeping warmer water closer to the surface. This still warm water at the top of the ocean had profound impacts on algal growth, a foundation species for ecosystems, but in completely opposite directions depending on the latitude where they occurred. In tropical regions, marine heatwaves caused a decline in this growth because it prevented nutrients from rising to the surface. However, closer to the poles where nutrients were plentiful but sunlight less so, marine heatwaves prompted rapid growth in algal blooms. Both responses have a direct impact on ocean productivity and the fisheries in these regions. This research is another step closer to improving our capacity to forecast marine heatwaves and their impacts right around the world.

But when it comes to impacts, the one that we most recognise in our daily lives is how we feel in the midst of a heatwave. However, the scale used by researchers to measure “thermal comfort” is a primitive one that has been designed for interior use. Its descriptions range from cold (-3), through neutral (0) too hot (3). This fails to take into account the affective state, such as whether something is pleasant or unpleasant; and many of the other comfort aspects that occur in outdoor environments including changes in wind, solar radiation and humidity. CLEX researchers with colleagues from the University of Sydney and Hong Kong Polytechnic came together to produce more meaningful climate descriptions than simple measures of wind speed, temperature etc. These new descriptions can then be used in research and or public announcements of weather conditions. Together the researchers created a multidimensional scale using plain language descriptors and then tested it with members of the public. The results showed non-professionals were able to consistently interpret this much more nuanced and evocative multi-dimensional thermal perception scale regardless of whether they were exposed to the actual thermal environment or not. In the future, our weather forecasts may be able to accurately describe how you will feel in the coming days.

Our ability to describe impacts and see how they change goes to the heart of making climate data useful to a wider range of research and industry partners. This is something that our students are also growing to understand. Recently, Charuni Pathmeswara saw this firsthand when she took part in a young professionals’ event organized by the NESP Earth Systems and Climate and Change (ESCC) Hub and jointly hosted by the Actuaries Institute and Engineers Australia. Her blog report of that event shows just how much climate data can impact many of our industries. Clearly, there will always be blue sky research involved in climate science but as the past four months has shown our results will increasingly lead to very practical outcomes for all Australians.