water levels rise at alarming rate in victoria, page-12

Hi Billybongo - don't know why you suggest this is just 'some reasoning after the fact' - you are wrong. The weather is consistent with what is expected with climate change. All weather is affected by global warming. ENSO events would be different today if not for global warming. There would not be as much water evaporating and falling as rain if not for global warming. Heat records wouldn't be as frequent or temperatures as high if not for global warming. There would not be fewer cold extremes if not for global warming, and winters would not be getting shorter, nights getting warmer, fewer frosts etc - if not for global warming.

If you are interested in climate I suggest you don't rely on your favourite newspaper columnist or radio host - or newspapers in general - but go straight to the science and learn for yourself, reading as widely as you can, Anyone who has done so knows that for decades scientists have been warning of the risks and likely changes we will have to deal with as a result of us emitting ever-increasing quantities of greenhouse gases. This includes extreme weather events - droughts, floods, storms etc; higher temperatures, more acidic oceans, longer growing seasons, reduced biodiversity etc etc.

Twenty years ago the models were too crude to give much confidence at the regional level (consider the advances in computers in the past twenty years). Models these days have access to vastly greater computing power - can probably process in a month what would have taken several years back then, and process in a few months now what would have taken years back then - allowing a greater level of confidence at regional level, but not as great as it will be in the future as computing technology advances and understanding of climate improves.

From the IPCC 1990-1992 assessment supplementary report: Australia - business as usual scenario (we are currently tracking near the top end of emissions of the business as usual scenario)

The warming ranges from 1 to 2C in summer and is about 2C in winter. Summer precipitation increases by around 10%, but the models do not produce consistent estimates of the changes in soil moisture. The area averages hide large variations at the sub-continental level.

The 2001 IPCC report referred to a more active hydrological cycle, among other things:

Examples of these include a more active hydrological cycle with more heavy precipitation events and shifts in precipitation, widespread retreat of non-polar glaciers, increases in sea level and ocean-heat content, and decreases in snow cover and sea-ice extent and thickness (see Table SPM-1).

There is a 2008 paper on Australian Parliament website (obviously written before the drought broke) - here is an excerpt (I've bolded some bits for emphasis:

Are extreme weather events-severe storms, flooding, droughts, heat waves or extremely violent cyclones-becoming more common? The answer appears to be 'yes'. Trends towards more powerful storms and hotter, longer dry periods have been observed, according to the IPCC's Fourth Assessment Report, and this trend is projected to continue. On the other hand, extreme cold-weather events are expected to decline in frequency, and for some regions of the world this will produce a positive impact, reducing health and infrastructure costs associated with freezing events.

Global warming is expected to cause an increase in weather extremes because it will change the distribution of heat and thus the flow of energy through the climate system. This will in turn alter the circulation patterns of the atmosphere and the oceans, and it will also modify the hydrological cycle by which water is circulated between the earth's surface and the atmosphere. Warmer temperatures mean greater evaporation, and a warmer atmosphere is able to hold more moisture�hence there is more water aloft that can fall as precipitation. However, many regional factors (ocean temperatures and currents, the location of mountain ranges, etc.) moderate this broad correlation. The frequency of heavy precipitation events has increased over most land areas, particularly over eastern parts of North and South America, in northern Europe, and northern and central Asia. The Rhine floods of 1996 and 1997, the Chinese floods of 1998, the East European floods of 1998 and 2002, the Mozambique and European floods of 2000, and the monsoon-based flooding of 2004 in Bangladesh (which left 60 per cent of the country under water), are examples of more powerful extreme events. There is also empirical evidence of more intense tropical cyclone activity in the North Atlantic since about 1970.

Rain falling in heavier bursts does not necessarily equate to more rain over a year�although this may occur in some regions. In fact, greater evaporation as the weather gets hotter may exacerbate droughts and desertification in dry regions. Climate change for these areas may mean that, when rain does come, it could fall in heavier bursts, which may be less useful than regular small amounts. Drying has been observed over the Sahel, the Mediterranean, southern Africa and parts of southern Asia. In Africa's large catchment basins of Niger, Lake Chad, and Senegal, total available water has decreased by 40 to 60 per cent, and desertification has been worsened by lower than average annual rainfall, runoff, and soil moisture, especially in southern, northern, and western Africa. Some regions of the earth have experienced 50-year drying trends, with some evidence linking the drying with lower rainfall associated with changing weather patterns in response to increasing sea surface temperature.

Australia is a naturally dry continent, which has been subject to periodic droughts throughout human history. One of the biggest questions for Australia is whether climate change will cause an increase in the severity, duration, frequency or distribution of droughts. CSIRO modelling suggests that the incidence of drought in some areas could triple by 2070, based on scenarios using different levels of carbon dioxide emissions. If accurate, such predictions indicate dire challenges for Australia's agricultural sector. However, CO2 concentrations are not the only factor in determining Australia's climate. The effects of the El Ni�o-Southern Oscillation (ENSO) on Pacific Ocean circulation and sea surface temperature, and variability in the Southern Annular Mode, which brings the rain-bearing westerly frontal systems across southeastern Australia, are key determinants of rainfall over the continent. Whether and how these phenomena might vary in a warmer world is currently the subject of intense research.