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A new study in Science Advances has found that intolerable bouts of potentially fatal humidity and heat are on the rise around the world, suggesting that worst-case scenario warnings about the impacts of the climate crisis are already happening. 

Humans’ ability to efficiently shed heat has enabled us to survive on every continent, but a wet-bulb temperature (TW) of 35°C marks our upper physiological limit. Previous climate models projected the first 35°C TW incidents by mid-century, and mostly in parts of the tropics and subtropics where humidity is already a problem. However, the study found that some coastal subtropical locations have already reported a TW of 35°C and that extreme humid-heat weather has more than doubled in frequency since 1979. Researchers identified thousands of previously undetected outbreaks of the weather combination in parts of Africa, Asia, Australia and South and North America, including several spots along the US Gulf coast. 

In the US, regions that experienced such extreme conditions dozens of times include eastern Texas, New Orleans and Biloxi, Mississippi. The most extreme incidents occurred along the Persian Gulf, where the heat-humidity combination surpassed the theoretical human survivability threshold on 14 occasions. 

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Slightly less extreme but more frequent outbreaks were detected across India, Bangladesh and Pakistan, north-western Australia and coastal regions along the Red Sea and Mexico’s Gulf of California.

Colin Raymond, lead author of the study, says, “Previous studies projected that this would happen several decades from now, but this shows it’s happening right now. The times these events will last will increase, and the areas they affect will grow in direct correlation with global warming.”

The team of researchers analysed hourly data from 7 877 individual weather stations, allowing them to pinpoint localised incidents.

In dry conditions, the body sweats out excess heat and evaporates it away, however humidity affects this evaporation and can even halt it in extreme conditions. If the body exceeds the threshold of survivability, organs will fail and lead to death within hours. 

Meteorologists measure the heat/ humidity effect on the ‘wet bulb’ scale. A normal internal human body temperature of 36.8° ± 0.5°C requires skin temperatures of around 35°C to remain comfortable. In theory, once the air temperature exceeds 35°C, humans will not be able to survive; this was the peak suffered in small areas of Saudi Arabia, Qatar and the UAE.

While some heat-humidity impacts can be avoided through acclimation and behavioural adaptation, humans can only withstand so much before survivability is impaired, even with perfect health, total inactivity, full shade, no clothing and unlimited drinking water.

Results suggest that under business-as-usual scenarios, wet bulb temperatures could regularly exceed 35°C in parts of South Asia and the Middle East by the third quarter of this century.

While air conditioning can mitigate the impact of heat-humidity, they are harmful to the environment and are not an option for most people in poor high-risk countries where subsistence farming is common. 

Featured image by: BrunoAmaru

Discourse around the climate crisis tends to focus on the weather-related effects, such as rising sea-levels and intense hydrological incidents such as flooding and droughts, as well as the direct impact on human lives, like famines, forced migration and geopolitical shifts. Less has been said about the impact the climate crisis could have on human conflict and the implications it could present for the future.

Cornell University professor Gary Evans explored this proposition and found a link between the climate crisis and large-scale social behaviour. He identified rising temperatures, increased frequency and severity of droughts, flooding and storms, and air pollution as the main drivers of climate change-related societal disruption. 

Evans categorised these impacts into three groups, namely heat, weather disasters and air pollution. This is how the fate of climate and society has intertwined: 

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An example conceptual model of climate change and its inter-relations with conflict and subsequent migration

Which current conflict is a direct result of climate change?

  1. Temperature, Mental Health And Quality of Life
    Starting from 1993, an 11-year long analysis of all deaths in the United Kingdom concluded that when temperatures exceeded 18°C, there was a 3.8% increase in the relative risk of suicide for each 1°C increase. Indeed, when ambient temperatures rise well above mean levels, mental health admissions to hospitals increase. However, while temperature is associated with mental health and quality of life, the direct association of rising temperatures with mental health is stymied by the complexity of suicide cases.

    A panel study examining 67 countries concluded that the warmer the coldest month of the year, the happier the country and the warmer the hottest month of the year, the less happy the country. The study included variables such as economic indicators, sociocultural factors and life expectancy to rule out alternative explanations for the differences in happiness.

    Furthermore, the study used projected changes in temperature to predict happiness levels over 30 and 60 years and found that as temperatures increase, countries at higher latitudes may become happier, while tropical and subtropical countries may become unhappier.

  2. Social Interaction, Crime and Conflict
    As the climate crisis intensifies, an increase in crime could be seen, particularly at lower latitudes. A study found that given existing US data on assaults, murders and annual temperatures in a set of 50 US cities over a 48- year period, an average annual increase of 2°F in the US would result in a staggering 24,000 additional murders/assaults each year.

    Studies looking at fluctuations in temperature in the same populations over time show increased intergroup conflict, especially in low income, agriculturally-dependant regions. For example, increased temperatures result in reduced rainfall, damaging crop yields and leading to economic distress and resource scarcity. Additionally, economic pressure caused by insufficient infrastructure and unemployment may exacerbate climate-related migration.

    The climate crisis may strengthen authoritarian trends globally, as discussed in a study published in the Journal of Environmental Psychology. Increased authoritarianism is directly linked to an increased perceived threat level; that is, situations that are troubling or distressing to an individual, which may result in populations becoming more polarised and discriminatory towards minorities and those at the margin of society.

    Eritrea is one such example. 5,000 refugees flee from its borders every month. Not incidentally, it’s one of Africa’s most food-insecure nations and and a one-party state with one of the worst human-rights records in the world.

  3. Armed Conflicts
    Armed conflicts over a 30-year period were coincident nearly 10% of the time with major heat waves or droughts and in countries with a high degree of ethnic fragmentation, the incidence was 23%. According to an article published in PNAS, this has far-reaching implications as countries vulnerable to climate change are set to suffer disproportionately from rising temperatures. The most fragile states often couple an economy of basic subsistence with deep ethnic divides. Middle Eastern countries with quarreling ethnic groups, for example Syria and Afghanistan, both experienced prolonged droughts that ravaged agricultural output at crucial moments in their recent history.

    The Pentagon also found a causal link between the climate crisis and human conflicts (for example, the ongoing Syrian conflict), but only when other conditions and factors such as drought severity and the pre-existing likelihood of conflict were present at a high enough level to ignite armed conflict.

Overall, Evans’s review indicates that behavioural changes stemming from rising temperatures will have mostly negative consequences and that without effective intervention, humans will become more violent and mental health will suffer.

A new study predicts that three quarters of the world’s major cities will experience dramatic climate shifts in their weather by 2050.


Environmental Predictions 2050

New York, San Francisco, and Washington will face unprecedented weather, while London will suffer from extreme drought by 2050, a recent study that analysed the impacts of climate change on the world’s major cities predicts. The effects of global heating will be so severe that the cities in temperate or cold zones in the northern hemisphere will be as hot as cities that are 1 000 km closer to the equator.

The research paper published in the peer-reviewed science journal PLOS ONE states that summers and winters in Europe will get considerably warmer by 2050, with average increases of 3.5C and 4.7C, respectively, compared with 2000. Water shortages will affect scores of cities in Europe as a result of the heating. The climate in London will look more like the climate in Barcelona, which suffered a major drought in 2018 resulting in millions of euros being spent on importing drinking water. Madrid will feel like Moroccan city Marrakech, Stockholm like Budapest, and Moscow like Bulgarian capital city Sofia.

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“New York City winters will be as warm as winters in Virginia Beach and wet Seattle will be as dry as San Francisco,” says the paper. “Washington D.C. will be more like today’s Nashville but with even greater variation in temperatures and precipitation.”

The residents of about a fifth of cities globally–including Jakarta, Singapore, Yangon, and Kuala Lumpur–will experience conditions currently not seen in any major cities in the world.  Rainfall will be a particular problem for such cities, with extreme flooding becoming more common alongside more frequent and severe droughts.

a) Cities in red – predicted to experience novel climate conditions. Cities in green – predicted to experience climate conditions similar to those of another major city. Size of dots represents size of change. b) The proportion of cities shifting away from the covered climate domain. c) and d) Extent of latitudinal shifts in relation to the equatorial line. Cities in blue – shifting towards the equator. Cities in yellow to red – shifting away from the equator. © 2019 Bastin et al./PLOS ONE

The researchers used state-of-the-art climate model projections of existing data. Analysing city pairs for 520 major cities in the world, they produced insights that are more meaningful to the common public. For instance, their interactive map shows different cities and their 2050 counterparts regarding weather patterns.

Cities’ Contribution to Climate Change

Cities are key contributors to climate change with urban activities causing the majority of greenhouse gas emissions. Estimates suggest that cities are responsible for 75% of global CO2 emissions, with transport and buildings being among the largest contributors.

Meanwhile, climate change is already impacting urban life across the world. With exceptional heatwaves striking across Europe last month, new temperature records were set in many cities in Belgium, the Netherlands and Germany as the mercury went above 40C. A new UK heat record was set with 38.7C in Cambridge.

In the US, millions of people were affected as the temperature soared in New York, Boston, Atlanta, and many cities in the Midwest. Millions in India also suffered as heatwaves and water shortages became severe in cities like Mumbai and Chennai. In Japan, more than 5,000 people from various urban centers sought treatment due to a heatwave in July.

Climate change will have costly impacts on cities’ basic services, infrastructure, housing, and health. It is essential, therefore, to make cities an integral part of the solution in fighting climate change by building more renewable energy infrastructures and introducing cleaner production techniques, and regulations or incentives to limit industrial emissions.


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