Leading report confirms critical climate changes

Posted 3 November 2016

Murray River BlackwaterThe duration, frequency and intensity of extreme heat events have increased across large parts of Australia, a leading biennial report has found.

The CSIRO and Bureau of Meteorology State of the Climate report has also noted considerable changes in rainfall patterns across the country.

The Bureau’s Manager of Climate Monitoring Dr Karl Braganza said the nation is already experiencing the effects of climate change.

“While the observations show us increased rainfall in some parts of [northern] Australia, we have also seen significant seasonal decline, such as in the April-October growing season where an 11% decline in rainfall has been experienced in the continental southeast since the mid-1990s,” he said.

“Australia experienced its three warmest springs on record in 2013, 2014 and 2015. Temperature and rainfall during this period is critical to southern Australia’s fire season.”

In the southwest of Australia, May-July rainfall had also reduced by around 19% since 1970.

CSIRO Senior Scientist Dr Helen Cleugh said climate changes were due to an increase in greenhouse gases such as carbon dioxide (CO2) in the atmosphere.

In 2015, atmospheric CO2 increases were the highest ever observed.

“Before around 1750, the level of CO2 was 278ppm. This year the earth will record a global annual average of over 400ppm, the highest level in the past two million years,” said Cleugh, who is also leader of the NESP Earth Systems and Climate Change Hub.

“Australian temperatures will almost certainly continue to increase over the coming decades. Temperature projections suggest more extremely hot days and fewer extremely cool days.

“As land temperatures increase, so do ocean temperatures and the report shows that the deep ocean is also impacted, with warming now recorded at least 2000m below the sea surface.”

The fourth biennial report also shows the number of days over 35°C each year has increased in recent decades, except in parts of northern Australia.

“Some of the record-breaking extreme heat we have been seeing recently will be considered normal in 30 years’ time,” Braganza said.

“The changing climate significantly affects all Australians through increased heatwaves, more significant wet weather events and more severe fire weather conditions.”

The report also looked at global trends and outlined a number of key findings:

  • 2015 was the warmest year since reliable global surface air temperature records began in 1880. The last 15 years are among the 16 warmest years on record.
  • Globally-averaged ocean temperatures and heat content are increasing. Observations reveal this warming extends to at least 2000m below the surface.
  • The globally-averaged sea level has risen over 20cm since the late 19th century, with about one third of this rise due to ocean warming and the rest from melting land ice.