Prepare for hotter days, says the State of the Climate 2020 report for Australia
- Written by Michael Grose, Climate Projections Scientist, CSIRO
The Australian State of the Climate 2020 report reveals a picture of long-term climate trends and climate variability.
The biennial climate snapshot draws on the latest observations and climate research from the marine, atmospheric and terrestrial monitoring programs at CSIRO and Bureau of Meteorology.
We are all still dealing with the lasting impacts of Australia’s hottest and driest year on record in 2019. It was a year of intensifying drought over eastern Australia, high temperature records and the devastating bushfires of summer 2019-2020.
State of the Climate 2020 puts all these events into the longer-term context of climate change trends and key climate drivers.
Sean Davey/AAPAustralia’s hottest year on record
Using the best available data, the Bureau of Meteorology estimates Australia has warmed on average by 1.44℃ (±0.24℃) between 1910 and 2019.
Read more: Weather bureau says hottest, driest year on record led to extreme bushfire season
Global rates of warming are lower due to the inclusion of the oceans in the global average, with the oceans experiencing a relatively slower rate of warming than continental areas.
The long-term warming trend increases the likelihood of extreme events beyond our historical experience. In 2019, natural climate phenomena that drive our weather, including a strong Indian Ocean Dipole and a negative Southern Annular Mode, added to the local warming trend, setting a record for the Australian average annual temperature.
This annual temperature for Australia is similar to what we might expect in an average year if the world reaches the +1.5℃ warming since pre-industrial times.
The long-term warming trend is also increasing the frequency of extreme warm days. We have seen a rise in the number of days when the Australian average temperature is within the top 1% ever recorded.
CSIRO/BoM, Author providedThe long-term temperature trend is also lowering the frequency of cooler years. The annual mean temperatures of Australia in the seven years from 2013 to 2019 all rank in the nine warmest years since national records began in 1910.
Barring unpredictable events such as major volcanic eruptions, projections show Australia’s average temperature of 2020-2040 is very likely to be warmer than the average in 2000-2020, as the climate system continues to warm in response to greenhouse gases that are already in the atmosphere.
What’s driving our changing climate?
Australia’s Cape Grim atmosphere monitoring station, in north-west Tasmania, is one of several critical global observing sites for detecting changes in the gas concentrations that make up our atmosphere.
CSIRO, Author providedThe increase in greenhouse gas concentrations has been the predominant cause of global climate warming over the last 70 years.
In 2019 the global average CO₂ concentration reached 410ppm, while all greenhouse gases combined reached 508ppm CO₂-equivalent, levels not seen for at least 2 million years.
Emissions of CO₂ from burning fossil fuels are the major source of the increase, followed by emissions from changes to land use. While the ocean and land have absorbed more than half the extra CO₂ emitted, the rest remains in the atmosphere.
The impact of the COVID-19 pandemic has reduced fossil fuel CO₂ emissions in many countries, including Australia.
Over the first three months of 2020, global CO₂ emissions declined by 8% compared to the same three months in 2019. But CO₂ is still increasing in the atmosphere.
Recent reductions in emissions due to COVID-19 have only marginally slowed the current rate of CO₂ accumulation in the atmosphere, and are barely distinguishable from natural variability in the records at sites such as Cape Grim.
Oceans warming and sea levels rising
Similar to surface temperatures over the continents, the State of the Climate report says sea surface temperatures are showing a warming trend that is contributing to an increase in marine heatwaves and the risk of coral bleaching.
Authors: Michael Grose, Climate Projections Scientist, CSIRO