''Looking beyond 2050, it becomes more difficult to assess risks to human health. But one thing is clear. The impacts of increasing temperatures upon human health are not linear. In a world in which temperatures are 4°C warmer than the pre-industrial base, we are likely to see health impacts many times more severe than those which will prevail in a world 2ºC warmer.''
Atmosphere of Hope:
Searching For Solutions to the Climate Crisis
by Tim Flannery in Australia
Text Publishing, $30
https://www.theguardian.com/environment/2015/aug/26/bushfires-heatwaves-and-early-deaths-the-climate-is-changing-before-our-eyes?CMP=share_btn_tw
When I wrote The Weather Makers, I laid out the state of climate science as it was understood in 2005. The book received much acclaim, but it was also criticised by climate-change sceptics as extremist and alarmist.
Since the book was published, the Intergovernmental Panel on Climate Change (IPCC) has completed two major summaries, in the form of its fourth and fifth assessment reports, and thousands of scientific publications have added to our understanding of how Earth’s climate system responds to carbon pollution.
As a result, many details of climate science have been clarified. Not only are the scientific projections of major trends more certain than ever, but today many of us also have firsthand experience of living in a strongly shifted climate. With climate change an experienced reality, and the science verified, the room for climate change denialism keeps shrinking.
Despite their vast increase in computational power, the models remain consistent in telling us that our Earth is warming, and will continue to warm in proportion to the volume of fossil fuel we burn. What has changed is the detail they reveal about the things that will unfold.
While no climate model can predict the future – simply because the future is impossible to predict – the increasing computational power of the models means that they are becoming ever more useful at explaining how climatic changes are being influenced by humanity. Studies of past climates are also becoming ever more informative. One that examines over 1,000 years of temperature records has shown that climate trends have sometimes differed markedly in the northern and southern hemispheres.
One example of hemispheric difference, which the sceptics used to cast doubt on the fact that CO2 causes warming, concerns the medieval warm period. The new study demonstrates unequivocally that this warm period was restricted to the northern hemisphere.
But such is the unprecedented volume of greenhouse gases that humans have released into the atmosphere that the climate system is being overwhelmed, and today warming is occurring in both hemispheres. The contemporary world is changing fast; few changes have been as profound or disturbing as the increases in extreme weather experienced right across the planet. For that dwindling band who continue to deny anthropogenic climate change, this is the new battleground – albeit one which is becoming ever more difficult for them to defend.
The link between extreme weather and climate change is a critical area for public understanding, because it’s the devastating extremes, rather than a shift in averages, that have the greatest impact. To deny the link also permits people to believe that climate change is something only for future generations to worry about. It is not.
Our climate has already changed, and over the last decade we have begun to witness more frequently the consequences of our profligate burning of coal, oil and gas. Very recent advances have allowed scientists to quantify the human impact on individual extreme weather events. Extremes in the weather are therefore a good place to begin looking at what has changed in climate science over the past decade.
Despite the long and loud warnings of the climate scientists that extreme heatwaves were all but inevitable, Rod Laver Arena had not been built to cope with the threat, and lives and money were put at risk. With millions of dollars at stake, the tournament organisers were reluctant to call an end to play. For day after scorching day the players slogged it out in 40°C+ temperatures on the courts. The fans stuck around too, though more than 1,000 had to be treated for heat stress. Finally, the health risks to both players and spectators became too much, and the multi-million dollar tournament was suspended.
In late 2014 Dr Thomas Knutson of the US Geophysical Fluids Dynamics Laboratory at Princeton University, New Jersey, and colleagues vpublished an analysis demonstrating that it is virtually impossible that the extreme heat experienced over Australia in 2013 could have occurred without the influence of human-emitted greenhouse gases. The analysis used a large series of computer models, some of which exclude human influence, while others include it.
The Australian heat of 2013 was so extreme than in the 12,000 simulations generated by the models that included only natural factors, in all but one simulation it lay outside the range of probabilities.
Moreover, human influence tripled the odds that heatwaves that year would occur as frequently as they did, and doubled the odds that they would be as intense as they were. Our ability to link some kinds of extreme weather to climate change in this way is very new, and is likely to revolutionise our understanding of how we are influencing Earth’s climate system.
The average temperature of Earth’s lower atmosphere has risen by just under 1°C during the past 200 years. How, you might ask, can such a small average increase have a large effect on extreme weather? There are several aspects that must be considered. One is that, because around 90% of the extra heat captured by greenhouse gases is transferred to the oceans, the oceans are warming dramatically. This alters evaporation, which influences the intensity of rainfall as well as the intensity of cyclones, and indeed the water cycle as a whole. But a second, more important, answer lies in the simple observation that if you plot weather for any location it looks like a bell curve.
During the summer of 2013, more than 3,000 weather records were broken in the US, while 123 such records were broken in Australia (which has far fewer weather stations). In 2014 a further 156 records were broken in Australia. We’re seeing the climate change before our eyes.
A well-documented heatwave experienced in Melbourne in January 2009 shows in detail how heat affects health. After four days of high night-time as well as daytime temperatures, many people’s bodies had become overstressed and unable to shed the excess heat. Mortality records reveal that, on average, around 90 people die annually in Melbourne between 26 January and 1 February.
But during the heatwave of 2009, 374 “excess deaths” were recorded, the great majority occurring after four days of the extreme heat. Bushfires and hurricanes might gain the headlines, but it’s easy to understand why doctors have come to dread what they call “the silent killer”.
Heatwaves have, of course, always occurred. The dustbowl-era American heatwave of 1936 was the hottest on record until 2012. The great Chicago heatwave of 1995, which killed about
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