365 Days of Climate Awareness 338 – AR6 Vol 2 Chap 11: Australasia

The increasing frequency and severity of extreme events in Australia and New Zealand has altered and in some cases done irreversible damage to a number of natural systems there. New Zealand’s seasons have changed, in a similar pattern as elsewhere worldwide: shorter, warmer winters and longer, hotter summers. A trend seen in New Zealand as elsewhere in the Pacific has been toward fewer, but more destructive, cyclones. Meanwhile precipitation has declined over the eastern part of the island, and increased on the west.

All images from the IPCC 6th Assessment Report, Vol. 2, Chap. 11. Increase in dangerous fire days, 2020-1985 mean compared to 1950-1985 mean.

Temperature trends, 1900-2020, in Australia and New Zealand.

As mobile species in both hemispheres shift their ranges toward the poles, but not all can follow. Kelp forests in formerly temperate waters have shrunk and many coral reefs, including large portions of Australia’s Great Barrier Reef system, have bleached with the rising temperature and acidity of the tropical ocean. Fish and other animals which can migrate with the warming waters find themselves in unfamiliar regions where ideal food and shelter are harder, or impossible, to find.

Precipitation trends, 1900-2020, in Australia and New Zealand.

Modeled runoff (10th, median and 90th percentiles) for high temperature rise (8.5°C/15.3°F) scenario.

Combined effects of global warming are having increasingly large composite effects on human systems. Heat alone has led to increased death rates throughout Australia, and has added to waves of illness, at times swamping Australia’s hospital system. As seen in other low-lying areas of the world, sea level rise has combined with high tides and storm surges to flood estuaries throughout Australia and New Zealand.

Stress on Australia's Great Barrier Reef system. (Top row) Degree heating weeks (duration and degrees in excess of coral bleaching temperature); (Middle row) Percentage of corals bleached; (Bottom row) Long-term coral recruitment (reproduction) mean (left) versus 2018 recruitment (right).

Anticipated likelihood for specific climate-related events, at the expected level of temperature rise. Left bars: low adaptation; right bars: moderate adaptation. (More dots = higher model probability.)

A spectacular example is the 2019-20 wildfires of southeastern Australia, which burned as much as 8.1 million ha/20 million acres, destroyed half or more of the range of over a thousand species, destroyed more than 3000 homes and directly killed 33 people. Nearly 500 more died in hospital from inhalation-related problems. The fires, made worse by an extremely hot and dry summer—an increasing climate trend in southeastern Australia—impacted agriculture, tourism and nearly every other sphere of life there.

Adaptation pathways.

Tomorrow: Central and South America.

Be brave, be steadfast, and be well.

IPCC 6th Assessment Report, Vol. 2, Chap. 11