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Hotter, more erratic weather and higher sea levels: CSIRO

Australia’s getting hotter — particularly at night, rainfall is erratic, carbon emissions are up and our sea levels are increasing at two to three times the global average. That’s the latest data to emerge from the State of the Climate 2012 report, which observes Australia’s climate and analyses the factors that influence it.

Scientists from the Bureau of Meteorology and the CSIRO worked together to produce the report, the second since the first State of the Climate report in 2010.

The data on global warming shows that annual-average daily maximum temperatures in Australia have increased by 0.75 degrees since 1910, with the majority of the increase occurring since 1970. Average Australian temperatures are expected to keep increasing, with a rise of 0.6 degrees (taking it to a total of 1.5 degrees since the 1980-1999 period) projected by 2030.

Nights are getting even warmer, with annual-average nightly minimum temperatures increasing by 1.1 degrees since 1910. Of that 1.1 degrees warming, 0.8 of it has occured since 1960. Each decade since the 1950s has been warmer than the last.

The frequency of record hot days has been more than double the frequency of record cold days in the last decade.

But there are obviously ebbs and flows in this heat increase. The years 2010 and 2011 were the coolest on record in Australia since 2001 due to La Niña. La Niña is the phenomenon of cooler ocean temperatures in the eastern equatorial Pacific — and warmer ocean temperatures near Australia — and often brings a strong increase in rain. Wet years are expected to become less frequent, with droughts expected to become more frequent in southern Australia (although heavy rainfall is also likely).

Despite the cooler last two years, a longer trend of warming is still present across the decade, and “warming trends observed around Australia are consistent with global-scale warming that has been measured during recent decades”, says the report.

The warming trend has occurred against a backdrop of natural, year-to-year climate variability,” it says. “Most notably, El Niño and La Niña events during the past century have continued to produce the hot droughts and cooler wet periods for which Australia is well known.”

Last year was the world’s 11th warmest year on record. The earth’s average surface temperature has increased by 0.8 degrees in the past century, while Australia warmed by 0.9 degrees.

The rate of warming differs across the land. This graph from BoM shows the increase in annual-average daily temperatures from 1960-2011:

Australia’s rainfall remains highly variable, with “many rainfall records” broken during the last two years of La Niña, says the report. Yet south-west Western Australia experienced its lowest level of rainfall on record in 2010 and only average rainfall in 2011.

The report highlighted “a general trend towards increased spring and summer monsoonal rainfall across Australia’s north during recent decades, and decreased late autumn and winter rainfall across southern Australia”.

This map of Australian autumn and winter (April to September) rainfall deciles from 1997 to 2011 shows whether the rainfall is above average, average or below average for the most recent 15-year period, compared to the entire rainfall record from 1900.

Regarding sea levels, 2011’s global-average mean sea level was 210mm (±30mm) higher than 1880 levels (the earliest year on record).

However, Australian records are even more concerning. Sea levels rose seven to eleven millimetres per year since 1993 in the north and north-west of Australia, which is two to three times the global average. Rates across the central east and southern coasts have been mostly aligned with the global average.

Sea-surface temperatures around Australia increased faster than the global average, reaching a record high in 2010 and nine months of 2011 featuring in the hottest 10 months on record. Again, this was largely due to La Niña, although the 2010-11 temperatures were higher than previous La Niña events.

Australia contributes about 1.3% of global carbon dioxide emissions, and in 2011 the concentration of CO2 in the atmosphere reached an 800,000-year high with 390 parts per million. Half of all carbon emissions stay in the atmosphere, while the rest are absorbed into oceans and land vegetation. The increase of CO2 in oceans accounts for a 30% increase in ocean acidity since pre-industrial times.

There are several acknowledgements of the human impact on carbon emissions and global warming including: “The main cause of the observed increase in CO2 concentration in the atmosphere is the combustion of fossil fuels since the industrial revolution” and “It is very likely that most of the surface global warming observed since the mid 20th century is due to anthropogenic increases in greenhouse gases.”

The State of the Climate report also discusses how recent extreme weather events can sometimes be explained in part by human influences on the climate, but not always. It notes that humans have had medium impact on the increasing frequency of heavy rainfall events, but notes that recent flooding in Australia is largely explained by the powerful La Niña episode. Cyclones are expected to be less regular but more intense.

The ABC’s Sara Phillips is sick of the constant reporting of the same message, since although the basic science — temperatures increasing, sea levels rising, weather unpredictability increasing — hasn’t changed for years, many people still don’t “believe” in climate change. Time to change the message up, writes Phillips:

For the message about climate change to be received and understood it needs to arrive in as many different forms as possible. Science, yes. But also climate change as a technological advance; a business opportunity; an economic reformation. Artists need to be recruited to paint climate change; writers need to write about climate change; it needs to be shown through interpretative dance. The message needs to come from different voices from all aspects of our diverse society: sports stars; comedians; accountants; ethnic leaders; church leaders; doctors; lawyers; professional associations.

“These messengers, like the scientists at the BoM and CSIRO, need to communicate on repeat. The same message, slightly new format, over and over.”

It seems CSIRO and BoM still feel the need to point out the obvious in the final page of their report: “CSIRO and Bureau of Meteorology observations provide further evidence that climate change is real.”

It does. The State of the Climate report also provides compelling evidence-based data that increasing greenhouse gas emissions will result in further global warming.

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