An atmospheric monitoring station on the north-west tip of Tasmania has recorded carbon dioxide measurements above 400 parts per million for the first time.

The regain was made at Cape Grim - the only station in the southern hemisphere for analysing baseline carbon levels.

The Cape Grim Baseline Air Pollution Station measures greenhouse gases like carbon dioxide, methane and nitrous oxide in samples of the particularly clean air of the Southern Ocean, .

The measurement comes just days after scientists warned that even the world’s cleanest air is hitting the 400ppm milestone.

CSIRO scientist Paul Krummel says it is concerning.

“It's probably one of the last places on Earth to actually reach this milestone, and it just highlights the ever-increasing levels of CO2 in the atmosphere,” he said.

“Globally, this is going to contribute to rising temperatures, which we are already seeing in the atmosphere.

“It's another milestone that we've reached where it's indicating that the health of the planet is probably in trouble.”

In related figures, NASA says last month was the hottest April on record globally.

It marks the seventh month in a row that monthly records have been broken.

More worryingly, it is the third month in a row that the monthly record has been broken by the largest margin ever.

It may not be surprising then, when faced with such clear evidence that climate variability is increasing, that the public are taking notice.

While bean-counters and hand-wringers baulk at the merest suggestion of bold moves to stop trashing the planet, strong climate change policy could win the upcoming election. 

The latest ReachTEL survey of 2,400 people suggests 64 per cent would be more likely to vote for a party that had a plan for 100 per cent renewable energy in 20 years.

Forty-eight per cent wanted to support a party that sought to push down Australia's net carbon emissions to zero by 2050.

Over 56 per cent of respondents said the government should do more on climate change.