The hot days in Sydney and Melbourne this week are 8 to 10 degrees hotter than usual for September as spring and summer becomes warmer in south-eastern Australia faster than the rest of the year. The highs of 29 degrees in Sydney on Tuesday and 24 degrees in Melbourne on Monday came as the landmark climate risk assessment released on Monday warned that historical data was no longer a reliable guide to future risk. The Albanese government is expected to announce its new target for 2035 this week, which it will take to the next United Nations climate conference in Brazil in November. In the Coalition, conservative MPs are threatening mutiny over its commitment to a net zero target. The Australian Academy of Science, the peak body for science, wrote in its recent submission to the Climate Change Authority that Australia needed to hit net zero much earlier than 2050 because its per capita emissions were higher than for all other developed countries.