Precision Climate Tracking of the Earth’s Response to Emission Reductions

About the research project

This Australian Research Council funded project addresses the urgent national and global challenge of tracking Earth’s response to our efforts in the mitigation of climate change. The project will develop near real-time indicators of the oceans response to our efforts to reduce emissions thus providing governments with the evidence that reductions in emissions are working. This will help Australia meet the Paris Agreement target of warming under 2 degrees. Precision climate tracking is new, very demanding of our existing observing and modelling systems, yet central to monitoring the health of the planet. We will provide current estimates of a range of essential climate variables such as ocean heat, sea-level rise and temperature and rain over Earth’s surface. We will focus on the Australasian region and Antarctica, framed within global context.

There are the following exciting new PhD projects associated with this program:  

Project 5: Determining the human-induced climate change and natural internal variations in the atmosphere.

More than 90% of the excess heat accumulated under anthropogenic climate change is absorbed by the ocean, which acts as a long-term memory within the climate system while also driving natural climate variability on seasonal to multi-decadal timescales. Major climate modes, including the El Niño-Southern Oscillation (ENSO), Southern Annular Mode (SAM), Interdecadal Pacific Oscillation (IPO), and North Atlantic Oscillation (NAO), strongly influence ocean circulation, heat content and salinity (e.g., Deser et al., 2010). These ocean changes are linked to large-scale atmospheric response in precipitation, temperature, winds and extreme events (e.g., Williams et al., 2022; Seo et al., 2023; Zhang et al., 2023). Ocean-driven atmospheric teleconnections are particular relevant for Australia and the Indo-Pacific region, where change in ocean conditions influence droughts, floods, and heatwaves (e.g., Ummenhofer et al., 2009; King et al., 2015; Rathore et al., 2021). At the same time, anthropogenic climate change is intensifying the global hydrological cycle and driving ocean warming, yet the interaction between these changes and climate variability remains poorly understood.

 

Despite the significant progress in climate change detection and attribution over recent decades, separating externally forced signals from internal variability remains challenging, particularly in atmospheric variables. Compared with the ocean, atmospheric fields exhibit a much lower signal-to-noise ratio due to the rapid and chaotic nature of atmospheric processes (Frankignoul et al., 2011). This makes the identification of externally forced variability in atmospheric fields more difficult than changes in ocean properties. At high-latitude regions where the weather noise can obscure weak but persistent ocean-driven signals, this can be particularly challenging. This HDR project aims to improve climate attribution by separating the influence of slowly evolving ocean variability from the rapidly fluctuating atmosphere. 

 

To address this challenge, the project will employ Linear Inverse Models (LIMs) and Green’s function approaches applied to ocean fingerprints associated with climate variability and anthropogenic climate change. Building on a novel ocean-based detection and attribution framework developed by Prof. Bindoff’s research group, this project will identify ocean states that characterise internal climate modes and externally forced change. LIMs provide a framework for extracting predictable low-frequency variability embedded within stochastic atmospheric fluctuations (e.g. Lou et al., 2021). Green’s function methods quantify the sensitivity of atmospheric and climate variables to spatially varying ocean conditions by constructing physically interpretable response operators that link atmospheric variability to ocean anomalies (Zhou et al., 2017; Zhang et al., 2023; Alessi et al., 2023). These approaches will be applied to CMIP6 and CMIP7 large-ensemble simulations, observations ocean datasets, and atmospheric reanalyses to quantify the impacts of internal variability and external forcing on precipitation, temperature, winds, circulation, pressure fields and weather extremes at both global and regional scales. 

This research will provide new estimates of the atmospheric footprint of ocean variability and anthropogenic climate change. These new estimates will improve our understanding of changes in climate risks and their influence on weather and climate extremes. For specific events, such as the 2026 European heatwave, they allow to formally quantify the fractional change in the event due to estimated underlying climate change signal. This fractional change is directly relevant to risk assessment, insurance and loss-and-damage frameworks, and to the development of climate adaptation and mitigation policies.

Project 6: Decoding the accelerating Atlantic-Pacific salinity contrast

               The Atlantic is saltier than the Pacific and Southern Ocean by up to ~ 2 (psu). This contrast in salinity is caused by (i) a surface freshwater flux asymmetry, with net evaporation minus precipitation (E-P) larger over the Atlantic by roughly 0.4-0.5 Sv, and (ii) ocean geometry and salt transport through the South Atlantic. The surface E-P flux asymmetry is sustained by the net atmospheric moisture export from the Atlantic to the Pacific (including the Southern Ocean) (Leduc et al. 2007). The ocean also carries salt through the upper-limb return flow, partitioned between the warm, salty Agulhas current from the Indian-Ocean and the cooler, fresher route from the Pacific through Drake Passage by the Antarctic Circumpolar Current (ACC); this sets the salinity entering the South Atlantic and hence the salt-advection feedback of the overturning circulation (Stommel 1961). 

Under greenhouse forcing this contrast is amplified via hydrological cycle intensification – “wet gets wetter, dry gets drier” over land and its ocean equivalent of “fresh gets fresher, salty gets saltier” (Held & Soden 2006; Durack et al. 2012). Durack et al. (2012) estimated a water cycle intensification of 8 ± 5 % per °C of surface warming, and Cheng et al. (2020) show the upper 2000 m salinity contrast index rose 5.2 ± 0.4 % over 1960-2017 and this intensification accelerated after 1991. The salinity contrast is dynamic rather than passive: North Atlantic salinity controls the formation rate of North Atlantic deep-water and thus strength and stability of the Atlantic Meridional Overturning Circulation (AMOC) via the salt-advection feedback. It influences the strength of Southern Ocean overturning circulations. This feedback is now flagged as possibly on a tipping trajectory (van Westen et al. 2024). Salinity is also our cleanest integrator of water cycle change and hence of the human influence on the earth’s hydrological cycle.

The aim of the project is to understand how the accelerating Atlantic–Pacific salinity contrast is partitioned between atmospheric and oceanic processes, and how its extremes are changing. The project will separate the slow human induced change from rising greenhouse gases on salinity from the fast residual variability. First, the fraction of the salinity contrast reflects changed atmospheric moisture transport versus ocean redistribution and how much is anthropogenic. Second, whether salinity governs the stability of the overturning circulation–the AMOC and Antarctic abyssal cell–more directly than temperature-based diagnostics, tracked through freshwater-transport diagnostics and ocean-model sensitivity experiments. Third, how do salinity (and precipitation-minus-evaporation) extremes evolve from the past into future scenarios, and where does that signal emerge first. Together these deliver the human fingerprint on ocean salinity, its links to overturning stability, and the changing character of ocean salinity extremes.

Join the team at IMAS working on this large scale ocean project funded by the Australian Research Council.

Primary supervisor

Meet Professor Nathan Bindoff

Funding

The successful applicant will receive a scholarship which provides:

• a living allowance stipend co-funded with ARC of $34,315 per annum for 3.5 years
• a relocation allowance of up to $2,000
• a tuition fees offset covering the cost of tuition fees for up to four years (domestic applicants only)

A tuition fee offset may be offered to eligible international applicants following competitive assessment 

As part of the application process you may indicate if you do not wish to be considered for scholarship funding.

Additional Funding

If successful, applicants will also receive a Precision Climate Tracking top-up scholarship of $5,000 per annum for 3.5 years. This scholarship is funded from ARC.

The Higher Degree Researcher is supported for travel, high performance computing, a programmer and two research associates, in addition to the research environment provided by IMAS. These resources, funded by an ARC Laureate project held by Bindoff "Precision Climate Tracking of the Earths Response to Emission Reductions" will support this PhD project to ensure they have access to appropriate compute resources, to be able to attend international workshops and conferences, and participate in projects with the associated research advisors who are part of the Laureate project.

If successful, international applicants will receive Single Overseas Health Cover (OSHC).

Other funding opportunities and fees

For further information regarding other scholarships on offer, and the various fees for undertaking a research degree, please visit our Scholarships and fees on research degrees page.

Eligibility

Applicants should review the Higher Degree by Research minimum entry requirements.

Ensure your eligibility for the scholarship round by referring to our Key Dates.

Selection criteria

The project is competitively assessed and awarded. Selection is based on academic merit and suitability to the project as determined by the College.

Additional essential selection criteria specific to this project:

• fundamental knowledge of maths and physics
• good understanding of meteorology and/ or physical oceanography
• excellent oral and written communication in English
• strong data analysis skills
• good programming and computational skills (preferably Python)

Additional desirable selection criteria specific to this project:

• knowledge of geophysical fluid dynamics
• skills in linear algebra and inverse theory

Application process

1. Select your project, and check that you meet the eligibility and selection criteria, including citizenship;
2. Contact Professor Nathan Bindoff to discuss your suitability and the project's requirements; and
3. In your application:
   • Copy and paste the title of the project from this advertisement into your application. If you don’t correctly do this your application may be rejected.
   • Submit a signed supervisory support form, a CV including contact details of 2 referees and your project research proposal.
4. Apply prior to 1 October 2026.

Full details of the application process can be found under the ' How to apply ' section of the Research Degrees website.

Following the closing date applications will be assessed within the College. Applicants should expect to receive notification of the outcome by email by the advertised outcome date.

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