State’s climate future revealed: Success is hot and failure is hotter

By 2090, Sydneysiders could swelter through another week’s worth of days above 35 degrees, and sea levels could rise 35 centimetres – and that’s if the Paris Agreement succeeds.

NSW and Australian Regional Climate Modelling released today includes a low-emissions scenario for the first time alongside the more pessimistic forecast.

A high-emissions scenario, in which greenhouse gas emissions and temperatures continue to regularly increase throughout the century, could deliver an average temperature increase of 3.8 degrees for Sydney, increase the number of hot days (above 35 degrees) by 20.4, the number of days of severe fire weather by 2.5, and push sea levels up by more than half a metre. Average winter rainfall could fall 35 per cent.

The low-emissions scenario, in which the globe achieves net zero by 2070, would deliver an average temperature rise of 1.2 degrees for the Sydney region by 2100 and an additional 7.3 hot days on top of the 8.1 hot days experienced now. Average winter rainfall could decrease by 20 per cent. The NSW government released updated NSW and Australian Regional Climate Modelling on Tuesday, which includes a low-emissions scenario for the first time alongside the more pessimistic forecast.

NSW Minister for Climate Change and the Environment Penny Sharpe said: “The data shows two clear options – we can do nothing which will lock in more extreme weather events in the future, or we can reduce emissions now to play our part in limiting the damage.”

A report from the Insurance Council of Australia on Monday said in the most recent “catastrophe season” – cyclones and severe storms that resulted in flooding between December 2023 and April 2024 – there was a 73 per cent jump in the number of insurance claims compared with the previous year. Actual insured losses rose only slightly, reaching $2.19 billion.

The publicly available modelling has projections for temperature, rainfall and sea level rise across the state at a resolution of four kilometres to give granular data for decision-makers such as Transport for NSW and local councils. The number of hot days is one of the most important for urban planning because extreme heat coupled with high relative humidity is lethal.

While the modelling shows that some climatic changes are baked in, it highlights the stark difference between countries achieving decarbonisation versus a business-as-usual approach. Across NSW, temperature projections for 2050 under a high-emissions scenario are expected to exceed the projections for 2090 under a low-emissions scenario.

Using 1990–2009 as the baseline, the average temperature in NSW is 17.7 degrees, with 37.6 hot days, 8.3 days of severe fire weather and 33.6 cold nights (below 2 degrees).

In the low-emissions scenario, the average temperature in NSW will increase by 1.2 degrees by 2050. By 2090, it will increase by 1.3 degrees, and there will be an additional 15.9 hot days, 3.5 days of severe fire weather and 10.6 fewer cold nights.

The high-emissions scenario increases the average temperature by 2 degrees by 2050 and 4 degrees by 2090. The number of hot days in a year will increase by 45.5 by 2090, and days of severe fire weather by 9.4, while cold nights will decrease by 24.1.

The changes in cold nights are only minor in much of NSW but dire in the Snowy Mountains, where a high-emissions scenario could lead to 70 fewer cold nights by 2090, and a low-emissions scenario would still mean 20–30 cold nights. This would greatly affect alpine ecosystems and ski resorts.

Rainfall will slightly decrease on average but remain variable, meaning dry spells can be followed by deluges. By 2090, the average winter rainfall is expected to be 20 per cent lower under a low-emissions scenario and 30 per cent lower under a high-emissions scenario. Under both scenarios, spring rainfall could decrease by 20 per cent for inland regions, including the Riverina Murray, Central West and Orana, and the ACT, but increase by 10 per cent on the North Coast.

The scenarios align with the five “shared socioeconomic pathways” of the United Nations Intergovernmental Panel on Climate Change. The low-emissions scenario is the second best of the IPCC’s pathways, based on achieving net zero globally by 2070 rather than 2050 and keeping global temperature rises under 2 degrees. The high-emissions scenario is the second-worst case, based on global warming remaining under 4 degrees.

The Paris Agreement spells out an intention to reach net zero limit warming to 1.5 degrees, but the pledges from the national government so far fall short of this.

Research from Bloomberg New Energy Finance on Monday suggests Australia is on track to miss its legally binding targets of net zero by 2050 and needs to increase its renewable energy targets to 87 per cent by 2030 rather than the current 82 per cent.

Climate change information can be distressing for some readers, with many Australians of all ages experiencing significant eco-anxiety.

For support visit AdaptNSW or call Lifeline 13 11 14.