Deadly Heat Waves Could Endanger 74% of Mankind by 2100, Study Says: A new online tool explores the number of days per year in places worldwide when heat is likely to exceed a deadly threshold if nothing is done about climate change.

Heat waves will spread farther around the world as global temps riseAn increasing percentage of the planet faces deadly heat for 20 or more days per year, with one-third of the world’s population currently at risk. Credit: Chris Hondros/Getty Images

Inside Climate News, June 2017

Deadly heat waves—already a risk for 30 percent of the world’s population—will spread around the globe, posing a danger for 74 percent of people on Earth by the end of this century if nothing is done to address climate change, according to a new study.

Nearly as alarming, the researchers project that even if greenhouse gases are aggressively reduced, at least 48 percent of the population will still face deadly heat waves by 2100 because of the amount of long-lived heat-trapping gases that already have accumulated in the atmosphere.

“We’re running out of good options for the future,” said lead author Camilo Mora, a biologist at the University of Hawaii at Manoa. “For heat waves, our options are now between bad or terrible.”

The new study comes as near-record heat is forecast for this week in California and the U.S. southwest, with the temperature expected to soar to 120 degrees in Phoenix, and as severe heat grips parts of Europe, contributing to forest fires that have killed at least 60 people in Portugal.

A handful of deadly heat episodes have made headlines in recent decades, including the 2003 European heat wave that was blamed fore more than 30,000 deaths; the 2010 heat wave in Russia that, along with wildfire smoke, contributed to more than 50,000 deaths; and the three-day 1995 Chicago heat wave that killed more than 700 people. But Mora and his team, in analyzing heat mortality episodes reported in peer-reviewed scientific literature between 1980 and 2014, found that deadly heat episodes are far more common and widespread than previously thought.

The researchers identified 911 papers with data on 1,949 case studies where human deaths were associated with high temperatures. They found that lethal heat waves had occurred in 164 cities across 36 countries. The team obtained climatic data for the times and locations of those episodes, including surface air temperature, relative humidity, solar radiation, wind speed and several other metrics.

The team was able to plot a threshold beyond which conditions are lethal, based both on temperature and humidity.

Sustained exposure to air temperatures at and above the human body temperature—98.6 degrees Fahrenheit (37 degrees Celsius)—can result in dangerous body heat accumulation. But humidity is also a key factor. When relative humidity is high, air temperatures around 90 degrees can become lethal, as sweating becomes less effective for dissipating the body’s heat.

The area of the planet where the deadly heat threshold is crossed for 20 or more days per year has been increasing, and now encompasses one-third of the world’s population—primarily at tropical latitudes, the team said in their study published today in the science journal Nature Climate Change. But with climate change, the risk will extend both south and north. An online tool released with the paper allows counting, for any place on Earth, the number of days per year when temperature and humidity would exceed such a deadly threshold—both today and in the future under different climate change scenarios.

For example, by the time children born today are in their 80s, New York will have 50 days per year with temperatures and humidity exceeding the threshold beyond which people have previously died due to hyperthermia, if no steps are taken to curb greenhouse gas emissions. Sydney would face 20 deadly heat days a year by 2100 and Los Angeles would face 30 under a “business as usual” scenario. The study notes that the consequences of exposure to deadly climatic conditions will be aggravated by an aging population, since elderly people are more vulnerable to heat mortality, and by increasing urbanization, because of the heat-trapping effect of asphalt surfaces, building materials, and reduced vegetation.

For Orlando and Houston, deadly heat would last the entire summer by 2100 without steps to reduce greenhouse gas emissions, the study projects. Indeed, even though the degree of future warming is projected to be greater in temperate zones and at the poles, the greatest risk to people from deadly heat events will be at zones closer to the equator, because of the additional impact of humidity.

“With high temperatures and humidity, it takes very little warming for conditions to turn deadly in the tropics,” said Iain Caldwell, a post-doctoral researcher at the University of Hawaii at Manoa, another of the paper’s authors.

The study bolsters previous research projecting increasing risk to humanity due to heat waves because of climate change.

Howard Frumkin, a professor of environmental and occupational health sciences at the University of Washington School of Public Health, who was not involved in the new study, notes it is difficult to project how many people will die in future heat waves—and the new research does not try to do so—because it is hard to predict how people will adapt to the changing climate, by increasing use of air conditioning, for example.

“That’s a two-edged sword,” notes Frumkin, one of the lead authors of the U.S. National Climate Assessment’s chapter on human health effects, most recently updated in 2014. “Until we power our air-conditioners solely with renewable energy sources, the steps we take to cope with the threat actually aggravate the threat,” he said. Frumkin also noted that the risk of severe, prolonged heat will be greatest for the poor, who often don’t have access to air-conditioning.

Overall, the study reinforces what we already knew: that large areas of the inhabited world will experience unprecedented levels of heat exposure in the next several decades, and that this hazard shift has significant potential implications for health,” said Jeremy Hess, another environmental and health sciences expert at the University of Washington, who was a co-author of the National Climate Assessment. Hess said a logical conclusion from the new research is that the U.S. exit from the Paris climate agreement, and the lessened effort to reduce greenhouse gas emissions that it represents, means that the risks will arrive sooner than if nations take aggressive action on climate change.

The increasing risk of heat mortality was one of the risks cited by the U.S. Environmental Protection Agency in 2009 when it adopted its finding that greenhouse gas emissions are a danger to human health and ecosystems. That endangerment finding was the legal foundation for the actions the Obama administration took to curb fossil fuel emissions.

Although the Trump administration is now seeking to undo most of those steps and to pull the United States out of the Paris climate accord, it has not yet sought to undo the endangerment finding, despite urging from some opponents of climate action.

Mora said that even though the team’s research projects the spread of deadly heat even under the most aggressive international policy to reduce greenhouse gas emissions, he hopes that the study helps spur such action.

His greatest fear, he said, is that people read the grim results as a reason to abandon effort as useless. On the contrary, Mora said, a delay in curbing greenhouse gas emissions will make the spread of heat mortality more difficult to manage and reverse.

“As bad as this is,” he said, “we cannot afford to give up hope.”

Marianne Lavelle is a reporter for InsideClimate News. She has covered environment, science, law, and business in Washington, D.C. for more than two decades. She has won the Polk Award, the Investigative Editors and Reporters Award, and numerous other honors. Lavelle spent four years as online energy news editor and writer at National Geographic. She also has worked at U.S. News and World Report magazine and The National Law Journal. While there, she led the award-winning 1992 investigation, “Unequal Protection,” on the disparity in environmental law enforcement against polluters in minority and white communities. She can be reached at PGP key:  

Additional excerpt from The Guardian

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.
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.

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.”

Without action to curb CO2 emissions, more than a third of the world could face climates that are different from anything observed anywhere today, a new study finds.

The research, recently published in Environmental Research Letters, follows hot on the heels of a recent paper in Nature Climate Change, which looked at how global temperature rise means that billions of people will experience climates that are “unusual”, “unfamiliar” and “unknown” in the future.

While the new study is similar, it goes a step further by considering how rainfall is likely to change in the future, as well as temperature.

Co-author Dr Erich Fischer, from the Institute for Atmospheric and Climate Science at ETH Zürich, presented the study at the recent European Geosciences Union General Assembly in Vienna. Carbon Brief caught up with him to discuss the research, which you can see in the video clip below.

Unprecedented climates

The researchers had started out looking for “climate analogues”. This means identifying climates that already exist somewhere in the world today that match the future projected climate of a particular location.

But what they found was that large areas of the world had no climate analogues. In other words, their projected future climate was like nowhere else on Earth at the moment.

You can see this in the map below. The green shading shows areas that would have climate analogues under 2C of warming, while the red shading indicates areas that would not. In between, the yellow shading shows regions that would have climate analogues for some seasons of the year, but not others.

It’s worth noting that the 2C of warming used here is relative to 1986-2005, rather than pre-industrial levels. This means the warming is about 0.61C more than the 2C limit set out in the Paris Agreement.

Map showing where projected future climates already do (green shading) or do not (red) exist somewhere today, under 2C of warming (relative to a 1986-2005 baseline). Yellow shading shows areas where future climates exist for some seasons only. Analysis takes into account future changes in both temperature and rainfall. Stippling indicates where more than 66% of the 35 models agree on the results. Source: Dahinden et al. (2017)

Map showing where projected future climates already do (green shading) or do not (red) exist somewhere today, under 2C of warming (relative to a 1986-2005 baseline). Yellow shading shows areas where future climates exist for some seasons only. Analysis takes into account future changes in both temperature and rainfall. Stippling indicates where more than 66% of the 35 models agree on the results. Source: Dahinden et al. (2017)

As you can see from the map, areas that will likely experience entirely new climates in the future are mostly found at low latitudes. This is because they are already hot today and have the lowest year-to-year variability, which means the signal of climate change emerges quickly from the noise of natural variability. But, as the paper notes, other parts of the world will also experience “unprecedented” climates:

“Climates that are likely to disappear with increasing warming are predominantly found in the northern high-latitudes, Andes, Central America, sub-Saharan Africa and southeast Asia.”

Overall, at 2C of warming, about 21% of the Earth’s land area would see climates that are different from anything observed anywhere today, the study says. At 1.5C of warming, this drops to about 15%, but at 4C of warming this increases to more than a third of the global land surface (34-44%).

Dahinden, F. et al. (2017) Future local climate unlike currently observed anywhere, Environmental Research Letters, doi:10.1088/1748-9326/aa75d7

IEA says we can (and should) get off of fossil fuels now – we can get to net zero worldwide, by 2060

In its new report, the IEA says:  “Technologies can make a decisive difference in achieving global climate goals while enhancing economic development and energy security. For the first time, [our] technology-rich modelling expands the time horizon to 2060 and reveals a possible although very challenging pathway to net-zero carbon emissions across the energy sector.”

The path to meeting this zero-by-2060 scenario is narrow and requires unprecedented action, the IEA says, though it does not rely on unforeseen breakthroughs in innovation. Its report emphasises the scale of the challenge:

“Deployment of clean energy technologies, inclusive of those currently available and in the innovation pipeline, is pushed to its maximum practical limits across all key sectors…This pathway implies that all available policy levers are activated throughout the outlook period [2014-2060] in every sector worldwide. This would require unprecedented policy action as well as effort and engagement from all stakeholders.”

Even so, its zero-by-2060 scenario would give only a 50-50 chance of keeping global temperature rise below 1.75C. This is within the bounds of the Paris goals, though the IEA says it is not trying to set the definition of the “well below 2C” target in the agreement.

Efficiency and renewables

Most of the emissions cuts in the IEA 2C and below-2C scenarios come from energy efficiency and renewables. To move from our current 2.7C path towards its 2C scenario, the IEA sees these two sectors providing 75% of the emissions reductions, with another 14% from carbon capture and storage (CCS), 6% from nuclear and 5% from fuel switching, for instance from coal to gas.

Shifting from the 2C path to its below-2C scenario would again put heavy emphasis on energy efficiency across transport, buildings and industry, to make 34% of the additional carbon savings. The importance of CCS would increase, making up 32% of extra effort, as the chart below shows..

Compared to the current path, efficiency and renewables would still play the largest role, as the chart below shows.

Cumulative emissions reductions to 2060, by source of savings. Source: IEA Energy Technology Perspectives 2017.

Cumulative emissions reductions to 2060, by source of savings. RTS is the IEA’s reference technology scenario, incorporating current policies and pledges. The 2DS and B2DS scenarios are for 2C and below 2C. Source: IEA Energy Technology Perspectives 2017.

As efficiency cuts demand and renewables scale up, fossil fuels’ share of the global energy mix falls from 82% in 2014 to 35% in 2060 under the 2C scenario, with coal use falling by 72%, oil by 45% and natural gas by 26% compared with 2014.

In the below-2C scenario these reductions are even more stark, with fossil fuels’ share of global energy falling to 26%, with coal use falling by 78%, oil by 64% and natural gas by 47%. Coal use without CCS is already largely eliminated in the 2C scenario, so the shift to below 2C disproportionately cuts into the space available for burning oil and gas.

Stranded fossils

In the power sector, low-carbon electricity meets 96% of global demand by 2060, even under the less ambitious 2C scenario. The IEA’s latest report goes further than ever before in spelling out the financial implications of this shift for coal and gas-fired power stations.

As the transition to zero-carbon accelerates, many fossil-fueled power stations will have to be closed before they reach the end of their natural life, the IEA says, causing lost earnings and creating “stranded assets” that are worth less than expected by investors.

Under its 2C scenario, some 1,520 gigawatts (GW) of capacity is closed early, of which 1,285GW is coal. For comparison, the combined fleets of China and the US today, the world’s top two countries for coal capacity, total 1,208GW. Adding Russia and Poland takes this to 1,285GW.

In its below-2C scenario, the IEA sees 1,715GW closing early, of which 1,330GW is coal. This is equivalent to the current fleets of China, the US, Japan, Germany and Poland. The plants closing early would lose $3.7tn in revenue to 2060 for the electricity they would otherwise have generated.

If action in the power sector is delayed, the extent of early closures and financial losses only increases, the IEA notes. If global power sector emissions remain flat until 2025, before falling more steeply later on, then losses could reach $8.3tn by 2060 and early retirements of coal and gas plants would climb to 2,350GW. The current global coal fleet is 1,965GW.

It’s worth noting that despite the significant role for CCS in its scenarios, the IEA says under a 2C or higher path: “Coal-fired power plants with CCS become too carbon intensive at a certain point, since 10-15% of their emissions are not captured.”

Unless these residual emissions can be eliminated through technical advance, then this issue will limit the potential to prevent stranded coal assets by adding CCS later on. That’s particularly true if climate ambition is pushed towards below 2C, or if action is delayed, the IEA report suggests.

Still, its scenarios include a key contribution from bioenergy with CCS (BECCS) to generate negative greenhouse gas emissions. The IEA includes significant levels of negative emissions, reaching nearly 5 gigatonnes of CO2 (GtCO2) per year in 2060, as the chart below shows.

Emissions to 2060 by sector in the 2C and below 2C scenarios. Source: IEA Energy Technology Perspectives 2017.

Emissions to 2060 by sector in the 2C and below 2C scenarios. Other transformation includes refineries, as well as biofuel or hydrogen production. For negative emissions, it could include biofuels linked to CCS or biogas used to produce hydrogen with CCS. Source: IEA Energy Technology Perspectives 2017.

Some experts argue this level of demand for biomass would be unsustainable, while others point to slow progress on CCS. Nevertheless, negative emissions from BECCS are “central” to the below-2C scenario developed by the IEA, where stubborn emissions from transport and industry are offset by negative emissions in the power and transformation sectors (for example, bioenergy-derived fuel production linked to CCS).


The broad outlines of what is needed to meet the goals of the Paris Agreement are well known: the world must reach net-zero emissions soon after 2050 to keep the rise in temperature to 2C or less. Yet the scale of the challenge is daunting and, as the IEA points out, most sectors are off track.

Part of its latest report is devoted to tracking the progress of clean energy, technology by technology, repeating a sobering reality check that it carries out each year. This year, the IEA says electric vehicles, energy storage, plus solar and wind are on track for a 2C scenario.

This compares poorly to the eight sectors that are not on track and the 15 sectors where more efforts are needed. While this picture appears fairly gloomy, it’s worth comparing to what the IEA said two years ago, when no sectors were on track, and last year, when only one was.

View image on TwitterView image on TwitterView image on Twitter

We’re not on track for 2C, but things are improving. Compare IEA indicators from 2015, 2016 and 2017:
(Zero, 1 then 3 are green)

It’s also worth reiterating the IEA’s view that meeting the aims of Paris is technically feasible with existing technologies and those in development, without the need for breakthrough innovation. As ever, world leaders’ lack of political will stands in the way of meeting their stated climate goals.
%d bloggers like this: