Climate Scientists Issue ‘Red Alert’ for Humanity – and Health 
Temperature, extreme heat and frost, and environmental disasters will increase in frequency, duration, and magnitude as the world warms, predicted a major new scientific report.

Climate change is now an existential health problem overshadowing all others, say scientists in a major report by the Intergovernmental Panel on Climate Change (IPCC) – the world’s largest and most comprehensive assessment of the state of the planet. 

Unprecedented changes in the Earth’s climate have been recorded in every region and the world is currently 1.09°C warmer than in the second half of the 19th century. The past five years have been the hottest on record since 1850.

The report links climate change with changing weather patterns, intensifying water cycles, rising sea levels, ocean acidification, thawing of permafrost, and increasing exposure to extreme heat. 

“The alarm bells are deafening, and the evidence is irrefutable: greenhouse gas emissions from fossil fuel burning and deforestation are choking our planet and putting billions of people at immediate risk,” said UN Secretary-General António Guterres in a statement in response to the report. “Global heating is affecting every region on Earth, with many of the changes becoming irreversible.”

The report, ‘Climate Change 2021: The Physical Science Basis’, was written by 234 scientists who are members of the IPCC Working Group I, and it was approved on Friday by 195 member governments of the IPCC. 

The landmark report is the first major review of the science of climate change since 2013, and the first instalment of the IPCC’s sixth assessment report, due to be released in 2022. 

“It has been clear for decades that the Earth’s climate is changing, and the role of human influence on the climate system is undisputed,” said Valérie Masson-Delmotte, IPCC Working Group I co-chairperson, in a press release

Temperature change projections from the IPCC report, which was published on Monday.

Extreme heat exposure threatens livelihoods and health 

Since 1970, global surface temperatures have risen faster than in any other 50-year period over the past 2,000 years, said the report. 

Changes in mean temperature and extreme heat and frost have already begun to occur and are expected to increase in frequency, duration, and magnitude as the world warms. 

It is “virtually certain” that hot extremes, including heatwaves, have become more frequent and intense across most regions since the 1950s, while cold extremes have decreased in frequency and severity, according to the authors.

Human-induced climate change is the main driver of these changes. 

“Heatwaves, floods, and droughts are taking thousands of lives, forcing displacement, and exacerbating food insecurity, hunger, and malnutrition,” said WHO on Twitter. “Climate change is the single biggest health threat facing humanity.”

Heatwaves can exacerbate respiratory and cardiovascular diseases, result in excess mortality, and cause power-shortages, leading to loss of health service delivery.

The health impacts from heatwaves can include dehydration, kidney diseases, respiratory disease, and heat stroke. 

Between 1998 and 2017, more than 166,000 people died due to heatwaves. The number of people exposed to extreme heat is rising – increasing by 125 million from 2000 to 2016.

If the world’s temperature warms by 1.5°C by the end of the century, populations will have a 1.6 times higher risk of experiencing extreme heat. This risk rises to 2.3 times higher risk at 2°C warming. If the world warms by over 3°C, the report projects that 80% of the world’s land area will be exposed to dangerous heat. 

Outdoor and manual workers are particularly at risk of the negative health impacts of extreme heat exposure.

“At increasing warming levels, extreme heat will exceed critical thresholds for health, agriculture and other sectors more frequently, and it is likely that cold spells will become less frequent towards the end of the century,” said the report. 

Extreme weather affects infrastructure, displaces people 

Changes in global monsoon precipitation have increasingly been observed since the 1950s, rising in some regions and falling in others as a result of greenhouse gas and aerosol emissions, said the report. 

Tropical cyclones have increased in frequency over the last four decades. The location in the western North Pacific where cyclones previously reached their peak intensity has now shifted northward.

“Human influence has likely increased the chance of compound extreme events since the 1950s,” said the report. “This includes increases in the frequency of concurrent heatwaves and droughts on the global scale; fire weather in some regions of all inhabited continents; and compound flooding in some locations.”

The annual occurrence of disasters has increased three-fold since the 1970s and 1980s, found a report by the Food and Agriculture Organization (FAO). Low- and middle-income countries (LMICs) bear the brunt of the disasters. 

Every year, environmental disasters result in 60,000 deaths, mainly in LMICs. There will likely be an increase in the number of people displaced by and suffering from injuries from extreme weather events.

Weather-related natural disasters destroy homes, infrastructure, medical facilities, and other essential services, disrupting health care delivery. 

Variable rainfall patterns and floods can affect the supply of fresh water, increasing the risk of diarrhoeal disease, respiratory infections, and affecting the transmission of vector-borne diseases. For example, residual water may serve as breeding grounds for disease-carrying mosquitoes. 

Climate change jeopardizes nutrition and food security

Today’s food systems are fragile and unequal, requiring widespread reforms in policies, farming practices, and financing.

Human activities have contributed to changing weather and precipitation patterns, along with agricultural and ecological droughts, impacting crop yields, nutrition, and food security.

“Several regions in Africa, South America and Europe are projected to experience an increase in frequency and/or severity of agricultural and ecological droughts, [while] heavy precipitation and associated flooding events are projected to become more intense and frequent in the Pacific Islands and across many regions of North America and Europe,” said the study. 

Climate change affects food production, availability, access, quality, utilization, and the stability of food systems.

As temperatures rise, crop yields are expected to decline, particularly in tropical and semi-tropical regions. Food security is already being affected in arid areas in Africa and high mountainous regions of Asia and South America. 

Rising temperatures and variable precipitation are likely to decrease the production of staple foods, particularly in LMICs. This will increase the prevalence of malnutrition and undernutrition, which currently cause 3.1 million deaths every year.

The loss of crop and livestock production from natural disasters can result in a total of 6.9 trillion lost kilocalories per year – the equivalent of the annual calorie intake of seven million adults.  

Increased carbon dioxide emissions lower the nutritional value of crops as temperatures rise. Previous studies by IPCC show that wheat grown at 546-586 ppm CO2 has 5.9% to 12.7% less protein, along with less zinc and iron. 

Almost 690 million people went hungry in 2019 and 45% of deaths among children under the age of 5 years are linked to undernutrition. These numbers could increase as climate change worsens food insecurity. 

“In a number of regions (Southern Africa, the Mediterranean, North Central America, Western North America, the Amazon regions, South America, and Australia), increases in one or more of drought, aridity and fire weather will affect a wide range of sectors, including agriculture, forestry, health and ecosystems,” said the report. 

Calls for urgent and large-scale actions to reduce emissions 

The report finds that unless there are immediate, rapid, and large-scale reductions in greenhouse gas emissions, the world will not be able to limit global warming to 1.5°C or 2°C above pre-industrial levels. 

Over the next 20 years, the global temperature is expected to reach or exceed 1.5°C of warming. 

“This report is a reality check,” said Masson-Delmotte. “We now have a much clearer picture of the past, present and future climate, which is essential for understanding where we are headed, what can be done, and how we can prepare.” 

The findings of the report “imply that reaching net zero anthropogenic CO2 emissions is a requirement to stabilize human-induced global temperature increase at any level,” said the authors. 

Emitting an extra 500 billion tonnes of carbon dioxide would leave only a 50-50 chance of staying under 1.5°C. The authors believe that 1.5°C of warming will be reached by 2040, but drastic measures to cut global emissions and reach net zero could slow or even halt the rise in temperatures.

“Stabilizing the climate will require strong, rapid, and sustained reductions in greenhouse gas emissions, and reaching net zero CO2 emissions. Limiting other greenhouse gases and air pollutants, especially methane, could have benefits both for health and the climate,” said IPCC Working Group I Co-Chair Panmao Zhai. 

“The message could not be clearer, as long as we continue to emit CO2 the climate will continue to warm and the weather extremes – which we now see with our own eyes – will continue to intensify,” said Corinne Le Quéré, Professor of Climate Change Science at the University of East Anglia in the UK and contributing author to the report. “Thankfully we know what to do: stop emitting CO2.”

It is too late for some of the effects of climate change, which are already irreversible for hundreds to thousands of years.

“If global net negative CO2 emissions were to be achieved and be sustained, the global CO2-induced surface temperature increase would be gradually reversed but other climate changes would continue in their current direction for decades to millennia,” said the report. 

“For instance, it would take several centuries to millennia for global mean sea level to reverse course, even under large net negative CO2 emissions,” the report said.

Messages to COP26 participants

The release of the report comes three months before a key climate summit, the 26th UN Climate Change Conference of the Parties (COP26), is set to be held in Glasgow. 

“The innovations in this report, and advances in climate science that it reflects, provide an invaluable input into climate negotiations and decision-making,” said Hoesung Lee, Chair of the IPCC.

“In my view, there are two key messages from the report for attendees at COP26. First, the report emphasises to climate negotiators – again – the need to reduce emissions further than currently looks likely in order to hit Paris targets,” said Nigel Arnell, Professor of Climate System Science at the University of Reading in the UK and a contributing author to the report. 

“Second, the report highlights – more urgently than the last report from 2013 – the importance of ramping up our collective efforts to adapt to our changing climate and increase resilience to more frequent and more extreme weather disasters in the future,” he said.

“Recent events have shown we are all exposed to climate risks,” Arnell added.

Extreme events are currently being felt across the globe, with wildfires in North America to floods in China, Europe, India, and parts of Africa, and heatwaves in Siberia.

Image Credits: Issy Bailey/ Unsplash, FAO.

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