Emissions from burning fossil fuels have accelerated since the global financial crisis, increasing the concentration of carbon dioxide in the world’s atmosphere to the highest levels in 800,000 years.
The findings come in a major review of climate observations by the CSIRO and the Bureau of Meteorology, which says carbon dioxide emissions from fossil fuels and land-use changes are tracking at the higher end of expectations.
The joint climate snapshot updates a similar review from the two peak scientific organisations in 2010, and comes months before Australia’s carbon price of $23 a tonne comes into effect on July 1.
The review finds Australia’s annual daily average temperatures have increased 0.9 degrees since 1910. Temperatures are projected to increase by 1 to 5 degrees across Australia by 2070 compared with the period from 1980 to 1999.
”Multiple lines of evidence show that global warming continues and that human activities are mainly responsible,” the report says.
Dr Karl Braganza, climatologist at the bureau’s National Climate Centre, said there were multiple indicators scientists use to track global warming, which the group had tried to include in the snapshot.
Among the report’s observations:
- global average sea levels in 2011 were 21 centimetres above the level in 1880, with the seas rising faster between 1993 and 2011 than during the 20th century as a whole.
- sea-surface temperatures have increased by about 0.8 degrees since 1910, with Australia’s sea-surface temperatures at a record high in 2010.
- heat content in the ocean continues to rise, increasing ocean volume and contributing to sea-level rise.
- there is a trend over recent decades towards increased spring and summer monsoonal rainfall across Australia’s north, but decreased late autumn and winter rainfall across the south.
Despite the long-term warming trend, 2010 and 2011 were the coolest years since 2001, on the back of consecutive La Nina events. But overall, each decade has been warmer than the previous decade since the 1950s, the report says.
Dr Paul Fraser, leader of CSIRO’s Changing Atmosphere unit, said greenhouse gases - including carbon dioxide, methane and nitrous oxide - have continued to increase.
Since 2000, fossil fuel emissions of carbon dioxide have increased by more than 3 per cent a year. There was a small decline of 1.2 per cent during the global financial crisis, but growth rebounded by 5.9 per cent in 2009 and 2010.
