Read Online The Best Australian Science Writing 2014 by Ashley Hay - Free Book Online Page A
Authors: Ashley Hay
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calculate the degree of fire danger, from âlow to moderateâ to âcatastrophicâ â this latter category was added in 2009 after the Black Saturday fires.
Climate change raises temperatures and, in some parts of Australia, leads to drier conditions. When it gets hotter or drier, bushfire risk increases. In southern Australia, increases in temperature and a decrease in spring rainfall in recent years have created a perfect storm of bushfire danger conditions.
Severe fire danger conditions, marked by an unusually high Forest Fire Danger Index, have increased particularly in the south-east since the 1970s. Not only is the danger becoming more intense, severe fire danger days are beginning to appear not just in summer but also in spring and autumn. In other words, the fire season is lengthening. The fire season is projected to continue to grow longer in coming decades, with even more days of extreme fire danger each year.
The bushfires that ravaged New South Wales in 2013 were striking, not just because of the magnitude of the blazes, but because they began unusually early, in September. A contributor to the early bushfire season was the fact that the state experienced its hottest September on record along with unusually dry conditions.
Perhaps paradoxically, global warming leads not only to an increased risk of fires but also to more intense rainfall. As heat builds up in our climate system, this accelerates evaporation of water from the ground and from water sources. This leads to more moisture in the atmosphere. But what goes up must come down, and one consequence is more heavy downpours. Since 1990, scientists have been predicting an intensification of the water cycle â both evaporation and rainfall â due to global warming. These predictions have been borne out by subsequent observations.
* * * * *
Over the past four decades, the amount of moisture in the atmosphere has increased by 4 per cent. Globally, thatâs equivalent to 900 Sydney Harboursâ worth of extra water in the air. Consequently, consistent with scientistsâ expectations, we have experienced an increase in heavy rainfall, particularly in north-western Australia.
Flooding can have a devastating impact on infrastructure and human lives. The Queensland floods in 2011 resulted in the deaths of 35 Queenslanders and cost the state $12 billion. The forces driving the floods were complex, with heavier than normal rainfall conditions accompanying La Niña conditions in the Pacific. At the same time, there were record high sea surface temperatures around Queensland. As with heatwaves and bushfires, global warming is increasing the risk from floods.
But in addition to more floods, we are also experiencingintensified drought. As it gets warmer and evaporation increases, the ground gives up moisture to the atmosphere. This means that drier regions become even drier, while wet areas are getting wetter. Global warming intensifies the water cycle.
While rainfall has overall increased across Australia, different regions have shown varying responses to global warming. North-western Australia has seen a strong increase in rain but in Australiaâs south and east, rainfall levels have decreased. The decline in the south has led to severely reduced water supplies in south-western Australia and the Murray Darling basin.
The change in rainfall patterns has several flow-on effects. Key food-growing areas in Australiaâs south-west and south-east are likely to experience more drought in coming decades, which will have consequences for agriculture. Drier conditions in the south-east, along with increased heatwaves, will combine to increase bushfire danger.
As cyclones travel across the sea surface, they scoop up energy from the ocean water. The warmer the water, the more energy cyclones build up. Ocean heat is fuel for cyclones. Scientists project that as global warming continues and oceans continue to warm, cyclones will grow
Climate change raises temperatures and, in some parts of Australia, leads to drier conditions. When it gets hotter or drier, bushfire risk increases. In southern Australia, increases in temperature and a decrease in spring rainfall in recent years have created a perfect storm of bushfire danger conditions.
Severe fire danger conditions, marked by an unusually high Forest Fire Danger Index, have increased particularly in the south-east since the 1970s. Not only is the danger becoming more intense, severe fire danger days are beginning to appear not just in summer but also in spring and autumn. In other words, the fire season is lengthening. The fire season is projected to continue to grow longer in coming decades, with even more days of extreme fire danger each year.
The bushfires that ravaged New South Wales in 2013 were striking, not just because of the magnitude of the blazes, but because they began unusually early, in September. A contributor to the early bushfire season was the fact that the state experienced its hottest September on record along with unusually dry conditions.
Perhaps paradoxically, global warming leads not only to an increased risk of fires but also to more intense rainfall. As heat builds up in our climate system, this accelerates evaporation of water from the ground and from water sources. This leads to more moisture in the atmosphere. But what goes up must come down, and one consequence is more heavy downpours. Since 1990, scientists have been predicting an intensification of the water cycle â both evaporation and rainfall â due to global warming. These predictions have been borne out by subsequent observations.
* * * * *
Over the past four decades, the amount of moisture in the atmosphere has increased by 4 per cent. Globally, thatâs equivalent to 900 Sydney Harboursâ worth of extra water in the air. Consequently, consistent with scientistsâ expectations, we have experienced an increase in heavy rainfall, particularly in north-western Australia.
Flooding can have a devastating impact on infrastructure and human lives. The Queensland floods in 2011 resulted in the deaths of 35 Queenslanders and cost the state $12 billion. The forces driving the floods were complex, with heavier than normal rainfall conditions accompanying La Niña conditions in the Pacific. At the same time, there were record high sea surface temperatures around Queensland. As with heatwaves and bushfires, global warming is increasing the risk from floods.
But in addition to more floods, we are also experiencingintensified drought. As it gets warmer and evaporation increases, the ground gives up moisture to the atmosphere. This means that drier regions become even drier, while wet areas are getting wetter. Global warming intensifies the water cycle.
While rainfall has overall increased across Australia, different regions have shown varying responses to global warming. North-western Australia has seen a strong increase in rain but in Australiaâs south and east, rainfall levels have decreased. The decline in the south has led to severely reduced water supplies in south-western Australia and the Murray Darling basin.
The change in rainfall patterns has several flow-on effects. Key food-growing areas in Australiaâs south-west and south-east are likely to experience more drought in coming decades, which will have consequences for agriculture. Drier conditions in the south-east, along with increased heatwaves, will combine to increase bushfire danger.
As cyclones travel across the sea surface, they scoop up energy from the ocean water. The warmer the water, the more energy cyclones build up. Ocean heat is fuel for cyclones. Scientists project that as global warming continues and oceans continue to warm, cyclones will grow
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