Sombre state of our climate

If you’re looking for a bit of good news at the end of a tough year it’s probably best if you don’t seek it in the Bureau of Meteorology (BoM) and CSIRO’s latest State of the Climate report, just released.

Key trends detailed therein include continued warming of Australia’s climate, an increase in extreme fire weather and length of the fire season, declining rainfall in the southeast and southwest of the continent, and rising sea levels.

The biennial report draws on the latest climate observations, analyses and projections to provide a comprehensive and scientifically rigorous analysis of Australia’s changing climate, present and future.

“Our science clearly shows that, due to increasing greenhouse gases, such as carbon dioxide, in the atmosphere, Australia’s climate is continuing to warm, and the frequency of extreme events such as bushfires, droughts, and marine heatwaves is growing,” says Jaci Brown, director of CSIRO’s Climate Science Centre.

Karl Braganza, BoM’s Manager of Climate Environmental Prediction Services, says the report finds the warming trend in Australia is contributing to increases in extreme fire weather and the length of the fire season.

“Climate change is influencing these trends through its impact on temperature, rainfall, and relative humidity, and the resulting change to the fuel moisture content,” he says.

A changing rainfall pattern is another key observation documented in the report, with contrasting trends being observed across the north and south of Australia.

“In the southwest and southeast of Australia we are seeing drier conditions, particularly in the cool season months of April to October,” says Braganza. “In southwest Australia, for example, cool season rainfall has decreased by around 16% since 1970. These trends are projected to lead to more time spent in drought in the coming decades.

“In contrast, rainfall has increased across most of northern Australia since the 1970s. While highly variable from year to year, there have been more ‘wetter than average’ years in recent decades.”

The oceans around Australia are also being affected by climate change, leading to significant impacts on marine ecosystems. Surface waters are acidifying, and the frequency, intensity and duration of marine heatwaves has increased.

COVID-19 lockdowns and the national economic downturn helped reduce global emissions in 2020 but they haven’t made a discernible impact on CO₂ levels in the atmosphere.

Measurements taken at the Cape Grim Baseline Air Pollution Station in northwest Tasmania show that atmospheric CO₂ levels have been increasing since pre-industrial times (around 1750), with fossil-fuel emissions the principal driver of this growth.

“To build a sustainable, resilient and productive future for Australia, governments, industries and communities need robust climate information,” says Brown.

“This report presents a synthesis of our most up-to-date understanding of the changing nature of Australia’s climate, providing a sound base for economic, environmental and social decision-making now and into the future.”

The full State of the Climate 2020 report is available on both the CSIRO and Bureau of Meteorology websites.