One of my intentions of this blog is to explore some of the impacts of climate change on the countries we pass through, so I had better start with Australia. The 4 degree or more conference which took place last month has provided me with the perfect armoury with which to do so. The premise of the conference was to attempt to describe what Australia would be like if global average temperatures were 4 degrees warmer than pre-industrial levels. This is the projected temperature increase which can be expected by around 2100 based upon the emission reduction pledges made at the Copenhagen and Cancun climate conferences. Listening to the predictions was the most depressing 2 days of my life, and can be summed up as essentially the collapse of civilisation as we know it. Whilst I had heard most of them before to be subjected to relentless  disturbing models and projections in presentation after presentation forced me to confront the bleak future which we face. It also brutally exposed the utter disconnect between the science and the current political  debate within Australia.  Current government policies are little more than a suicide note for future generations but you wouldn’t know it from reading the papers.

Australia, already a hot and dry continent will be particularly hard hit by climate change. So what would it be like in a 4 degree warmer world. The first thing to note that the warming would be greater than 4 degrees – average temperatures would be greater over land compared to the ocean and the warming more pronounced nearer the poles. Australia would be at least 5 degrees warmer and up to 7 especially in the centre. The warming would also become more pronounced over time and by 2030 all decades will be warmer than previous ones.

Rainfall is harder predict due to natural variability and uncertainty over the impact of a warmer world. Climate Change will create greater precipitation globally mainly around the equator and towards the poles, but all the climate models predict that mid latitudes (around 25 to 30 degrees south of the equator – where southern Australia lies) will become drier.  However the models do disagree at precisely which latitude this will occur. Currently it is difficult to discern future patterns from historical patterns due to the naturally large variations in rainfall experienced across much of Australia. However it is possible that a drier pattern is emerging in South East Australia. Much clearer is the case of south west  Western Australia which has seen a 20 % reduction in average rainfall over the last 20 years. In the last year it has received only 5% of the average rainfall for the past 100 years. It is likely this will continue and that other parts of southern Australia will also receive less rain especially in winter and spring. More northern  regions are likely to see higher rainfall.

 

Fig 1

Percentage of climate modelling experiments showing future increases in annual precipitation

Source CSIRO

Warmer temperatures cause higher evaporation rates from plants, water bodies and soils. A warming of 4 degrees will increase the rate of evaporation of standing water by 10 to 20%, it is much harder to measure and therefore predict changes to evaporation from soils and plants but the change is likely to be similar. Drier soils mean less run off into rivers and water storages, indeed Western Australia has seen a 70% decline in inflows into its dams in the south west. It is likely that Perth will be highly dependant on desalinated water in a warmer world. For other areas the incidence of droughts will also increase with a doubling for the Murray Darling Basin and four times as likely for Melbourne for a mid range climate scenario. Once we get to a 4 degree warmer world droughts will be 40 times more likely to occur in some areas!!!

Anologues

Extreme weather events are also likely to increase with global warming although at a slower rate than the increases in average temperatures.  The European heatwave in 2003 which killed thousands of people will become the norm in 30 years and will be cold in 60 years. It will be a similar story for Australia. The conditions which created Black Saturday in 2009 where temperatures were 6 degrees greater than normal will become common place.  See table below for number of days with temperatures above 35 degrees.

There will also be increases in extreme rain events such as those which hit Queensland and Victoria this year, this will  be the case even where overall rainfall averages decline. There will also be an increase in hail storms which hit eastern Australia. Cyclones are predicted to decline in frequency but those that do occur are likely to be more severe.

Sea levels will rise both due to melting ice but also the thermal expansion of water – as it heats up its volume increases. By 2100 if global temperatures reach 4 degrees sea levels are predicted to increase by 1.1m with another 7 m to come over the next century or two. Given that 80% of the population live within 50km of the coast this will pose a particular problem for Australia. A 1.1m rise coupled with a very high tide would see both Sydney and Brisbane airports inundated along with tens of thousands of houses.  Even with a rise if only 0.5m events that happen now every 10 years would happen about every 10 days and current once in a 100 year events could occur several times a year!!!

Fig 2

Estimated number of residential buildings at risk of inundation from a 1.1 m sea-level rise (including 1-in-100-year storm tide for NSW, Victoria, and Tasmania and high tide event for others)

Source CSIRO

So what would all this mean for Australia. Warmer drier areas will see an increase in the severity and occurrence of bushfires. Very high danger fire weather will increase by 20 to 100% and extreme by 100 to 300%. Australia’s biodiversity already under severe stress will be hit hard. 70% of our native vegetation has been cleared or modified since Europeans arrived, and only 9% could be described as “structurally intact”. Australia already has the highest rate of mammal extinction of any continent and that’s before climate change has even kicked in.  Australia has a large number of endemic species and contains between 7 to 10 % of all global biodiversity. Many of those species can tolerate very narrow climatic ranges, for example 53% of Eucalypt species have a temperature range of less than 3 degrees. As temperatures increase they will be forced to move to cooler areas either by going up higher or by moving South. Each degree increase would require around a 100m increase in altitude or a 125km shift south. Thus a 4 degree warming would require a shift of 450km. As Australia is very flat there is limited scope for altitude migration. This will hit alpine regions very hard with most alpine habitats predicted to be lost by 2100. Freshwater environments will also be seriously impacted not only from reductions in rainfall, but as most river systems run from west to east unless species can fly or walk over land they will be unable to move south to maintain a habitable climate and many will die or have significantly reduced populations reducing the biodiversity of the habitat. It is estimated that climate change will increase the extinction rate by a factor of ten (which is already between a hundred and a thousand times the background rate – ie the rate which would be expected without humans).  And these aren’t just a bunch of fluffy animals either, they are what we rely on for clean air and water, soil fertility, erosion prevention etc etc etc.

Other unique environments likely to be hit are Kakadu and the Great Barrier Reef. 90% of Kakadu’s freshwater systems are likely to be inundated by sea level rise by 2100. The coral reefs are facing a double threat firstly  temperature rises are causing coral bleaching to occur. This is where the coral becomes stressed and the symbiosis between the coral and the algae which it hosts and is dependant on for nutrients breaks down causing the algae to die making the coral more susceptible to diseases and eventual death. It was unknown before 1980 and since then there have been 6 large events which have increased with frequency and extent since then. For the first time ever reefs off the coast of Western Australia experienced bleaching this year. Corals are also highly sensitive to changes in ocean chemistry. The ocean is absorbing much of the carbon dioxide being emitted by human activities.  This reduces the Ph of the ocean which reduces the availability of carbonate ions which the coral use to build their structure. Since 1990 there has been a 15% reduction in the calcification across parts of the Great Barrier Reef. If nothing is done mass bleaching will be an annual occurrence by 2030 -2040. A temperature rise of only 1.5 degrees will see 80% of coral reefs at a high risk of disappearance, this is anticipated to occur by 2050. Whilst  atmospheric CO2 concentrations greater then around 450ppm will cross the boundary of the minimum concentration of carbonate in the ocean required to maintain reef structure.

Climate change will also have a dramatic impact on agriculture.  Higher temperatures, increased evaporation and more extreme weather events will all lead to reduced crop yields as will the projected fall in rainfall during the growing season for cool season crops. A four degree warmer world coupled with projected changes in rainfall is likely to see a 10 – 30% decrease in wheat production and a decline of up to 50% is not outside the realms of possibility. A 10% decline in rain causes a 30% decline in river flow and consequently a reduction in the availability of water for irrigation.  By 2070 the CSIRO estimates that Mildura will experience 60 days per year over 35 degrees which will call into question the viability of current agricultural practices.  Pests and diseases will also increase as will prices and price volatility. It is predicted that Australia will move to become a net food importer, although given that most other food producing regions will be experiencing similar changes it’s not clear where this food is going to come from!!! Livestock will also be severely impacted, with a 4 degree warming half of Australia will experience temperatures which induce heat stress every day!!!!

Of course it’s not just animals that experience heat stress human health will also suffer as a result of global warming. Over 2,000 people are estimated to have died prematurely from the effects of heat on Black Saturday and the days immediately preceding it.  Conditions that favour the spread of infectious, water and food borne diseases are likely to flourish with climate change, and the distribution of mosquito borne diseases such as malaria and Japanese encephalitis will spread. For example dengue fever is predicted to spread as far south as Sydney.

There will also be a severe cost of living impact. Insurance premiums will sky rocket as natural disasters increase, indeed many homes in low lying areas under threat from flooding or sea level rise will simply become un-insurable forcing tax payers to pick up the tab. Already according to Munich Re the world’s largest re-insurer the incidence of natural disasters worldwide has tripled since 1960 with economic costs increasing 900%.

A warming of 4 degrees will increase peak electricity demand in Adelaide, Melbourne and Brisbane by 25%, and higher temperatures will increase transmission losses, both of which will inevitably increase electricity prices. Increasing food prices caused by declining production not only in Australia but also world wide will put further pressure on household budgets. Local and State Governments will also face budget pressure as infrastructure will need to be updated, repaired or replaced in response to changing climate, extreme weather and sea level rise. Water infrastructure will require to be modified as current water requirements cease to be met through rainfall in water catchments alone.  This will either require large scale reliance on energy hungry desalination or a whole scale shift in how we use water, for example water re-cycling, grey water use and domestic rainfall harvesting.  Some remote communities will simply become too unpleasant to be habitable and there populations will be forced to re-locate.  The heat island effect (where dark surfaces in cities absorb more heat than vegetation would) mean that even our major cities will become pretty unpleasant, increasing temperatures by as much as 7 degrees!!!!

With huge price hikes, tax rises, stress on health services and infrastructure, people losing their homes through extreme weather events and sea level rise, and the heat causing the fraying of tempers it’s not hard to imagine social order beginning to break down.

In short Australia will be a pretty nasty place in which to live (except perhaps Tasmania) in a warmer world. The costs, human, ecological and financial will be astronomical. Far better to pay now than a whole lot more later.