Lethal Heating: 06/21/17

21/06/2017

A Third Of The World Now Faces Deadly Heatwaves As Result Of Climate Change

The Guardian - Oliver Milman

Study shows risks have climbed steadily since 1980, and the number of people in danger will grow to 48% by 2100 even if emissions are drastically reduced

'For heatwaves, our options are now between bad or terrible,' says the lead researcher behind the new study. Photograph: Gerard Julien/AFP/Getty Images

Nearly a third of the world's population is now exposed to climatic conditions that produce deadly heatwaves, as the accumulation of greenhouse gases in the atmosphere makes it "almost inevitable" that vast areas of the planet will face rising fatalities from high temperatures, new research has found.
Climate change has escalated the heatwave risk across the globe, the study states, with nearly half of the world's population set to suffer periods of deadly heat by the end of the century even if greenhouse gases are radically cut.
"For heatwaves, our options are now between bad or terrible," said Camilo Mora, an academic at the University of Hawaii and lead author of the study.
High temperatures are currently baking large swaths of the south-western US, with the National Weather Service (NWS) issuing an excessive heat warning for Phoenix, Arizona, which is set to reach 119F (48.3C) on Monday.
The heat warning extends across much of Arizona and up through the heart of California, with Palm Springs forecast a toasty 116F (46.6C) on Monday and Sacramento set to reach 107F (41.6C).
The NWS warned the abnormal warmth would "significantly increase the potential for heat-related illness" and advised residents to drink more water, seek shade and recognize the early symptoms of heat stroke, such as nausea and a racing pulse.
Mora's research shows that the overall risk of heat-related illness or death has climbed steadily since 1980, with around 30% of the world's population now living in climatic conditions that deliver deadly temperatures at least 20 days a year.
The proportion of people at risk worldwide will grow to 48% by 2100 even if emissions are drastically reduced, while around three-quarters of the global population will be under threat by then if greenhouse gases are not curbed at all.
"Finding so many cases of heat-related deaths was mind blowing, especially as they often don't get much attention because they last for just a few days and then people moved on," Mora said.
"Dying in a heatwave is like being slowly cooked, it's pure torture. The young and elderly are at particular risk, but we found that this heat can kill soldiers, athletes, everyone."

Indian children bathe with buffalos during a heatwave. Photograph: Jaipal Singh/EPA

The study, published in Nature Climate Change, analyzed more than 1,900 cases of fatalities associated with heatwaves in 36 countries over the past four decades. By looking at heat and humidity during such lethal episodes, researchers worked out a threshold beyond which conditions become deadly.
This time period includes the European heatwave of 2003, which fueled forest fires in several countries and caused the River Danube in Serbia to plummet so far that submerged second world war tanks and bombs were revealed. An estimated 20,000 people died; a subsequent study suggested the number was as high as 70,000.
A further 10,000 died in Moscow due to scorching weather in 2010. In 1995, Chicago suffered a five-day burst of heat that resulted in more than 700 deaths.
However, most heat-related deaths do not occur during such widely-covered disasters. Phoenix, for example, suffered an unusually hot spell last June that resulted in the deaths of at least four people. Hyperthermia, an excess of body heat, can lead to heat stroke and a potential inflammatory response that can kill.

Dying in a heatwave is like being slowly cooked, it's pure torture
Camilo Mora, researcher

Mora said the threshold to deadly conditions caries from place to place, with some people dying in temperatures as low as 23C. A crucial factor, he said, was the humidity level combined with the heat.
"Your sweat doesn't evaporate if it is very humid, so heat accumulates in your body instead," Mora said. "People can then suffer heat toxicity, which is like sunburn on the inside of your body. The blood rushes to the skin to cool you down so there's less blood going to the organs. A common killer is when the lining of your gut breaks down and leaks toxins into the rest of your body."
Global warming is a potent instigator of deadly heat, with research from University of California, Irvine this month finding the probability of a heatwave killing in excess of 100 people in India has doubled due to a 0.5C increase in temperature over the past 50 years.
"The impact of global climate change is not a specter on the horizon. It's real, and it's being felt now all over the planet," said Amir AghaKouchak, UCI associate professor and co-author of that study.
"It's particularly alarming that the adverse effects are pummeling the world's most vulnerable populations."
Elevated temperatures and dry conditions have been exacerbated by the clearing of trees, which provide shade and cooling moisture, in urban areas. Mora said that while adaption such as government heat warnings and the increased use of air conditioning has helped reduce deaths, this was not a viable long-term solution.
"The heat means that we are becoming prisoners in our own homes – you go to Houston, Texas in the summer and there's no-one outside," he said.
"Also, the increased use of air conditioning means that electrical grids fail, as has happened in New York City, Australia and Saudi Arabia. We need to prevent heatwaves rather than just trying to adapt to them."

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Tropics In Trouble As Rising Heat, Humidity Push Populations To The Edge: Study

Fairfax - Peter Hannam

Rising temperatures and humidity will make the world's tropics increasingly unliveable by pushing more people to the thresholds of their physical tolerance and beyond, a new international study finds.
As of 2000, about 30 per cent of the world's population lived in regions where the climate exceeds deadly threshold levels – based on temperature and relatively humidity levels – for at least 20 days a year, researchers publishing in the Nature Climate Change journal estimate.

Earth's killer heat will get worse
A new global study says deadly heat waves will grow in frequency, intensity and duration, affecting 75 per cent of the world's population if greenhouse emissions are not reduced.

Even with the most optimistic scenario for greenhouse gas emissions reductions, that share will rise to about 48 per cent by the end of the century. If so-called business as usual emissions continue, that share would climb to 74 per cent by then, the paper found.
"You are going to have all of those people in the tropics 'cooking' there because they are not going to have any possibility to cope with this [increase in heat and humidity]," said Camilo Mora, the paper's lead author and an associate professor in the Department of Geography at the University of Hawaii, Manoa.
The research examined studies of 783 cases of excessive human deaths from heatwaves between 1980 and 2014. These included the 70,000 deaths from a huge European heatwave in 2003 and more than 10,000 deaths in Russia in 2010.
Professor Mora noted that identifying heatwave mortality rates was difficult because the causes – such as heart attacks and other organ failure – may only surface some time after the event.
"I think there is a huge underestimate of that even in developed countries," such as in Europe, North America and Australia, he said. For developing nations with poorer record keeping, the deaths could be larger still.
Even though tropical areas, including northern Australia, were not projected to warm as much as regions further from the equator, conditions are already near tolerance levels with further warming forecast.

A family cools off in a stream during a heat wave last month in Islamabad, Pakistan. Photo: AP

"For many of these tropical places, the whole year becomes a heatwave," he said.
Air-conditioning offered some relief but would make people "prisoners of their own homes" – so long as electricity supplies didn't fail, Professor Mora said.

People cool off in a spray from a broken water pipe during a heat wave in Karachi, Pakistan last month. Photo: AP

Sophie Lewis, a heatwave specialist at the ARC Centre of Excellence for Climate System Science, said the study highlighted how poorer populations in particular were going to struggle.
"If we're seeing an increase of 100 days a year that might be deadly in places that rely on subsistence agriculture, it's going to be pretty hard for people to be outside working," Dr Lewis said.
The paper provided an interactive graphic that estimated the populations most at risk under different emissions scenarios.
The chart [below] shows the risks under the most ambitious scenario of cuts out to 2100, based on the so-called 2.6 representative concentration pathway (RCP).

At the highest pollution scenario, the RCP8.5 pathway, most of the world's tropics face high risks by the end of the century.(See chart below.)

The heatwave report comes as much of south-western US faces a severe heatwave in coming days, particularly California and Arizona.

IMAGE

For populations at higher latitudes – such as Perth, Adelaide, Melbourne and Sydney – humidity levels may decline with future warming but those gains would be at least partly reversed by rising temperatures.
Soils, for instance, are becoming drier in those regions, reducing the moisture available for evaporative cooling, Professor Mora said. The process works much like a human loses heat through sweating.
"Unfortunately the mid-latitudes are drying out so much, the energy is retained there like a rechargeable battery," he said.

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Are Heatwaves ‘Worsening’ And Have ‘Hot Days’ Doubled In Australia In The Last 50 Years?

The Conversation - Andrew King

What exactly does research say on heatwaves and hot days? AAP Image/Tracey Nearmy

The release of the Finkel report has refocused national attention on climate change, and how we know it's happening.
On a Q&A episode following the report's release, Climate Council CEO Amanda McKenzie said we've seen:

… worsening heatwaves, hot days doubling in Australia in the last 50 years.

Excerpt from Q&A, June 12, 2017. Quote begins at 2:12.

Her comment provides the perfect opportunity to revisit exactly what the research says on heatwaves and hot days as Australia's climate warms.

Examining the evidence
When asked for sources to support McKenzie's assertion, a Climate Council spokesperson said:

Climate change is making hot days and heatwaves more frequent and more severe. Since 1950 the annual number of record hot days across Australia has more than doubled and the mean temperature has increased by about 1°C from 1910.
Specifically, there has been an increase of 0.2 days/year since 1957 which means, on average, that there are almost 12 more days per year over 35°C.

You can read full response from the Climate Council here.

How do we define 'heatwaves'?
Internationally, organisations use different definitions for heatwaves.
In Australia, the most commonly used definition (and the one used by the Climate Council) is from the Bureau of Meteorology (BOM). It provided the first national definition of a heatwave in January 2014, describing it as:

A period of at least three days where the combined effect of excess heat and heat stress is unusual with respect to the local climate. Both maximum and minimum temperatures are used in this assessment.

The BOM uses a metric called the "excess heat factor" to decide what heat is "unusual". It combines the average temperature over three days with the average temperature for a given location and time of year; and how the three day average temperature compares to temperatures over the last 30 days.
We can also characterise heatwaves by looking at their their intensity, frequency and duration.
Researchers, including Australian climate scientist Dr Sarah Perkins-Kirkpatrick, are trying to standardise the definitions of "heatwaves" and "hot days" and create a framework that allows for more in-depth studies of these events.

Are heatwaves 'worsening'?
There's not a large body of research against which to test this claim. But the research we do have suggests there has been an observable increase in the frequency and intensity of heatwaves in Australia. Research published in 2013 found a trend towards more heat waves in Australia between 1951 and 2008.
A review paper published in 2016 assessed evidence from multiple studies and found that heatwaves are becoming more intense and more frequent for the majority of Australia.
The following chart shows heatwave days per decade from 1950 to 2013, highlighting a trend toward more heatwave days in Australia over time:

We've seen a trend towards more heatwave days over Australia. Trends are shown for 1950-2013 in units of heatwave days per decade. Stippling indicates statistical significance at the 5% level. Adapted from Perkins-Kirkpatrick et al. (2017)

Have hot days 'doubled' in the last 50 years?
While the number of "hot days" (as defined by the BOM) has not doubled over the last 50 years, as McKenzie said, the number of "record hot days" certainly has. "Record hot days" are days when the maximum temperature sets a new record high.
Given that McKenzie made her statement on a fast paced live TV show, it's reasonable to assume she was referring to the latter. Let's look at both figures.
The BOM defines "hot days" as days with a maximum temperature higher than 35°C. The BOM data show there were more hot days in Australia in 2013, 2014, 2015 and 2016 than in any of the 50 years from 1966 to 2016 (the last year for which data are available).
In fact, there were more hot days in the years 2013-2016 than in any other year as far back as 1910. If we compare the decades 1966-76 and 2006-16, we see a 27% increase in the number of hot days.

Number of 'hot days' per year, 1966-2016

Hot days' are defined by the Australian Bureau of Meteorology as days with a maximum temperature higher than 35°C. Source: Australian Bureau of Meteorology

The following map shows the trend in the number of days per year above 35 °C from 1957–2015:

Bureau of Meteorology

A 2010 Bureau of Meteorology/CSIRO report found record hot days had more than doubled between 1960 and 2010. That data was collected from the highest-quality weather stations across Australia.

Number of record hot day maximums at Australian climate reference stations, 1960-2010. Bureau of Meteorology 2010

Number of days in each year where the Australian area-averaged daily mean temperature is extreme. Extreme days are those above the 99th percentile of each month from the years 1910-2015. Bureau of Meteorology

Why are heatwaves worsening, and record hot days doubling?
The trend in rising average temperatures in Australia in the second half of the 20th century is likely to have been largely caused by human-induced climate change.
Recent record hot summers and significant heatwaves were also made much more likely by humans' effect on the climate.

The human influence on Australian summer temperatures has increased and we can expect more frequent hot summers and heatwaves as the Earth continues to warm.

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