- Asia-Pacific Disaster Alerts
- Bureau of Meteorology - Global Climate Change and Variability Images
- NASA - Global climate change resources
- Bureau of Meteorology - Australian climate change statistics
- Australian Bureau of Statistics - Natural Disasters in Australia (1895-2007)
- Australian Bureau of Statistics - How do we know about climate change in the period before instruments?
- Brave New Climate- How hot should it have really been over the last 5 years?
- Bureau of Meteorology - Annual Australian Climate Statement 2011
- IPCC 2011 Special Report on Extreme Events
- Great natural disasters 1950–2007 (percentage distribution worldwide) - Munich Re
- Climate Change 2007: Synthesis report - IPCC
- Geo Natural catastrophes 2007 - Munich RE
- Great natural disasters 1950–2007 (number of events) - Munich Re
- Hurricane and Extreme Weather and Climate Connections, Greg Holland, National Center for Atmospheric Research
Evidence of a warming Australia
According to the Bureau of Meteorology, Australia's annual mean temperature for 2010 was 22.00°C. It has now been nine years since Australia experienced a below-average year and the past ten years (2001 to 2010) were the warmest decade on record for Australia.
BOM states that, 'the period from May to October, considered to be northern Australia's dry season, conditions were abnormally wet. Northern Australia had its wettest dry season on record, measuring an average of 190mm of rainfall, compared with the previous record of 176mm in 1978. June was the only month to see the widespread dry conditions that are typical of the season. September was a particularly notable month for rainfall, coming in as the wettest on record for northern Australia with an average of 51mm, well above the previous record of 33mm set in 1906.'
Variability is part of the trend
Natural variability is a feature of Australian weather records over time. 2007 was a La Nina event instead of El Nino, which helps to explain why 2008 was cooler on average across Australia than other recent years. These trends are reflected globally.
Thermal inertia: Key risk factor
There is a time delay between when concentrations of CO2 particles in the atmosphere increase causing atmospheric temperature rise, and when ocean temperatures rise. In other words, there's a time lag between when the Earth begins to experience an energy imbalance and when the climate fully responds to it. This "thermal inertia" factor is the central risk factor in assessing severe weather trends. Here's what Nathan Lewis from CalTech University, in interview with ABC Radio National, has to say about this risk:
"You see the Earth has a 35 year thermal inertia and so what we're doing now is only the beginning because we're waiting 35 years even to see the effects of what we did 35 years ago. So it would be another 30 years until we started to really see, even at the only 380 parts per million level [of C02-e atmospheric concentration] that we're doing now, what those effects are.
And we'll be at 550 [parts per million of C02-e contentration] by then - or more - and it's never been above 300. So there's a serious debate over whether that will be very bad or not, very bad, but all we know is no matter what we do when we get there there's no turning back."
Dr. Nathan Lewis, Professor of Chemistry, California Institute of Technology
Insurance evidence of escalating climate change impacts
Although the evidence is sparse and difficult to compare given changing data gathering techniques, scientists are closely assessing the risk that weather related natural disasters are climbing in line with a warming planet. The past 19 out of 20 major Australian insurance events were weather related, and this increase reflects European insurance findings.
The graph below developed by Munich Re, the world's largest re-insurance group, highlights the significant increase in economic and insurance losses (the dollar cost of damage done and the portion of this cost that was insured) when we compare great weather related disasters during the 1990s compared to previous decades.
Some portion of this dollar comparison arguably is due to reasons other than climate change such as growing capital investment, population and migration to areas where disasters hit. But even the raw data on the number of 'natural' catastrophes shows a consistent increase. As Munich RE noted in 2010 'the only plausible explanation for the rise in weather-related catastrophes is climate change'.
In their 2011 summary (of 2010) they concluded that the 'high number of weather-related natural catastrophes and record temperatures both globally and in different regions of the world provide further indications of advancing climate change.'
Increasing extreme weather evidence
According to the US National Centre for Atmospheric Research, the world has seen a 5-10% increase in precipitation over the past century. The frequency of heavy rainfall events generally is likely to rise with global warming, increasing the potential for flooding. This supports the overall extreme weather trends highlighted in IPCC evidence provided by the Centre for Research on the Epidemiology of Disasters (CRED) which is shown in the graph below.
The potential for extreme weather events to occur much more frequently is linked to the evidence of rising sea levels. In 2001, the IPCC predicted an annual rise of less than 2mm in the next decade. In 2007, the IPCC reported that between 1993 and 2006, sea levels actually rose by 3.3mm a year. An annual rise of 3.3mm is right at the upper limit of the IPCC's predictions. Most scientists specialising in this area believe we will experience more at least a one metre rise in sea levels by the end of the century. This means that one-in-one-hundred-year-events could happen much more frequently in vulnerable areas as highlighted below.
Human induced climate change and hurricane activity
According to Greg Holland from the US National Centre for Atmospheric research in a 2009 presentation, 'it is likely that the annual numbers of tropical storms, hurricanes, and major hurricanes in the North Atlantic have increased over the past 100 years, a time in which Atlantic sea surface temperatures also increased.' The slide below refers to evidence from the North Atlantic - an area where relatively good records exist compared to other parts of the world. This evidence is driving deep and not yet conclusive debate within the global scientific community about the links between climate change and severe weather patterns.