They have done Australia a massive disservice. Because the document has major implications to the way we live our lives in the next 50 years. It contains an up-to-date snapshot of observations and analysis (html version, pdf version) of Australia’s climate and the factors that influence it. The data was sourced from peer reviewed data on temperature, rainfall, sea level, ocean acidification, and carbon dioxide and methane levels in the atmosphere. Between them, CSIRO and BOM, have 160 years of research behind them so there ought to be a fair degree of trust of their data.Among their key findings is the long-term upward trend of temperature of Australia. On average temps have risen 0.7 °C in the last half a century. Some areas have warmed 1.5 to 2 °C in that time. The strongest warming is occurring in spring (about 0.9 °C) and the weakest in summer (about 0.4 °C). The number of days with record hot temperatures has increased each decade over the last 50 years and the years 2000 to 2009 was Australia’s hottest decade on record. Rainfall has been stable since 1960 though the geographic distribution has changed significantly. Rainfall is on the rise in remote northern areas such as the Pilbara, the Northern Territory coastline and the Gulf of Carpentaria. But rainfall has decreased in south-west and south-east Australia, including all the major population centres, during the same period.
The report looked at 137 years of ocean data and found the global average sea level rose by close to 200mm in that time. The speed of the rise is also increasing. In the 20th century sea levels rose at an average of 1.7mm per year. But since 1993, the rise is about 3.0mm per year. There are geographical variations within the 1993-2009 figure. In Australia sea level rises are higher in the north and west (7-10mm per year) while rising just 1.5 to 3mm in the south and east. The oceans are absorbing a quarter of all human generated CO2 making them more acidic affecting the health of ocean ecosystems around the world.
It doesn’t help global carbon dioxide and methane emissions are on the rise. The natural range of CO2 in the atmosphere has been 170 to 300 ppm (parts per million) for the past 800,000 years. But emissions have been rising rapidly in the last century and were up to 386ppm by 2009. Methane emissions were steady for most of human history around the 650 ppb (parts per billion) but have shot up to more than 1700 ppb in recent years.
The evidence points to glaringly obvious conclusions: Australia is becoming hotter, the heavily-populated areas are becoming drier, and human activities have caused most of the damage since 1950. The CSIRO and the BOM deal with probabilities so they are “only” 90 percent sure of that last fact. But I would not want to be backing the one in ten possibility. As the researchers baldly conclude “our observations clearly demonstrate that climate change is real”. Which makes all the more surreal, reactions from some recalcitrant MPs and media decision makers.