The experts on the Intergovernmental Panel on Climate Change (IPCC) state it categorically: our increasingly warm climate will pose a threat to human beings much sooner that we think. What are the mechanisms of this rise in temperature, and what consequences will it have? Here we take stock of a hot topic!
Whose fault is global warming?
The Earth has switched between cold periods and extreme heat before, as the climate changes naturally. But these phenomena that used to take millions of years are now happening much more quickly, within barely more than 100 years! So what’s causing that? Human activity that generates greenhouse gases which drive temperatures up. Unfortunately, it takes a century for them to dissipate. So even if we halted all emissions of CO2 and methane (the two main greenhouse gases) today, the atmosphere’s temperature would still rise by around 1°C by the end of the century… One little degree that would, however, mean real upheaval for the environment. For example, a variation of 1°C either way means that ice will melt or not melt. Some life forms, animals or plants which will be unable to adapt to this overly fast change, will be heavily impacted. And we’re heading for an increase of at least 2°C…
From global warming to the greenhouse effect
Every second, the sun’s rays hit the Earth and warm the ground. The ground emits infrared rays, which are released into the atmosphere along with this heat. But greenhouse gases (mainly CO2, methane and nitrogen protoxide) and water vapour form a kind of filter that keeps some of this heat in. Thickened by the build-up of greenhouse gases, this “cloud” allows fewer and fewer infrared rays to escape, and turns into a “lid” which keeps them in along with the heat emitted by them. That’s the greenhouse effect. And that’s why we refer to these gases as “greenhouse gases”. They prevent the rays from getting through, keep the heat in and drive the temperature up. It started out as a natural phenomenon, which is now thrown out of balance and amplified by human activities.
What are greenhouse gases?
These gases come from means of transport that run on petroleum-based fuels (planes, boats, cars), industrial activities powered by coal and gas combustion (electricity generation and heating), factory-style livestock farming and its consequences (deforestation to make way for cereal crop cultivation for animal feed, fertilisers, slurry fermentation, machine use, etc.).
- Excess carbon dioxide (CO2) in the atmosphere is mainly down to human activities, like the use of fossil fuels (petrochemical oil, natural gas and coal used by industry, for heating and means of transport), cement production and changes to land use (deforestation, agriculture and urban sprawl). This excess CO2 is the biggest culprit behind the additional greenhouse effect, and therefore global warming, observed since 1750.
- Methane, which takes around 10 years to disappear (compared to 100 years for CO2), has a “warming” effect that’s 28 times greater than that of CO2. And the concentration of methane has increased a great deal over the last century because of factory-style farming, marshland fermentation processes, ruminants and discharges.
- Nitrogen protoxide, which is naturally emitted by soil, comes not least from the use of nitrogen-based fertilisers in farming.
- Ozone, which occurs naturally at an altitude of 20 km, can also be emitted in the low-lying layers of the atmosphere due to compounds given off by means of transport.
Which countries emit the most CO2?
According to a report by the NGO Carbon Disclosure Project (CDP), in conjunction with the Climate Accountability Institute, dating back to July 2017 and based on figures in the public domain, 25 countries – out of the 200 in the world – are said to be behind more than half of the carbon dioxide emissions recorded since 1988. Among them, and in order), are China with 10 gigatons of CO2 per year in 2017, the USA (5 GT per year), India (2.5 GT per year), Russia (1.7GT per year), Japan (1.2GT per year) and Germany (1.8 GT per year).
The order is different if we look at CO2 emissions per capita. There, Qatar takes the lead with 30 tons per capita per year, followed by Curaçao with 23 tons per capita per year, then Kuwait, the United Arab Emirates, Gibraltar, Bahrein, Saudi Arabia, Australia, Canada, the USA and Luxembourg. Countries which are big exporters (like China) bear the brunt of the responsibility for it, whereas they mostly produce goods for other countries. Europe boasts about having drastically cut its CO2 emissions, whereas in fact, due to the relocation of production to factories and industries in Asia, it’s just emitting them on a different continent…. Which changes nothing as far as the planet is concerned!
Are fossil fuels the big culprits of global warming?
Again according to the report by the NGO Carbon Disclosure Project (CDP) in conjunction with the Climate Accountability Institute, 71% of CO2 emissions are attributable to just 100 companies, primarily those that produce the fossil fuels which are the main culprits behind global warming. The companies with the most significant ecological impact are: China Coal (14.3% of worldwide greenhouse gas emissions), the Saudi Arabian Oil Company (4.5%), Gazprom (3.9%), National Iranian Oil (2.28%), Exxon Mobil, Suncor, Shell, BP and Total (the only French company on the list, with 1% of emissions). So fossil fuels (petrochemical oil, natural gas and coal) are the main lever to counter global warming.
Les conséquences du réchauffement The consequences of global warming
The consequences of global warming impact on public health with health risks like epidemics, and also on farming, production and therefore the economy, as much as on the increasing frequency of extreme meteorological events like cyclones and drought.
The extinction of flora and fauna
Some animal species are going to go extinct, with a domino effect on the food chain, as well as plants, reducing biodiversity even further. Moreover, the disturbances can also be chemical in nature. CO2 is partly absorbed by the sea, makes seawater acidic and has disastrous consequences on marine ecosystems like coral reefs.
Disruption of the sea
L’augmentation de la température des océans empêche la photosynthèse du phytoplancton, c’est-à-dire sa capacité à produire de l’oxygène ce qui entraîne une désoxygénation des zones The increase in the temperature of the sea prevents photosynthesis (i.e. the ability to produce oxygen) in phytoplankton. This leads to widespread deoxygenation of the sea. Proximity to the sea also places islands and coastal cities under threat, either because they are sinking or because the sea level is rising. Venice immediately comes to mind here, but also affected are Miami and Jakarta, the capital of Indonesia. The city is certain to be partly submerged by 2050, and will have to… Relocate!
Climatic and meteorological disturbances
While climate change does not directly cause hurricanes and cyclones, it does make them more severe, more frequent and more lengthy. Episodes that used to be rare or seasonal occurrences, like heatwaves, are happening more frequently. In some parts of the world, temperature and humidity conditions will be such that living there will become untenable. Near the equator, by 2050, life will no longer be possible, on the one hand because of the heat, and on the other due to the consequences of this rise in temperature on the ecosystem, water, ability to cultivate crops, etc. Here in France, at least, the rise in temperature will close the gaps between the seasons. In southern countries, it will rain even less often and droughts will be even more severe. As for regions covered with ice or snow, they will see their surface area shrink, meaning that they then reflect the sun’s rays away to a lesser extent, and therefore warm up the ground further. It’s a real vicious circle: the more these cold surfaces disappear, the more the temperature rises, and the more the temperature rises… The more the surfaces melt!
What effects does this have on human health?
Floods, heatwaves and changes to ecosystems related to rising temperatures will have an effect on the occurrence, transmission and spread of viruses. It’s already the case for the dissemination of infectiousness diseases carried by mosquitoes. For example, if a region gets 1-2°C warmer, the tiger mosquito – native to tropical forests – migrates a little further north. But this species, which is one of the world’s most invasive, has become accustomed to temperate urban areas. Already found in 80 countries – including France, since 2004 – this mosquito is taking over the whole planet. A vector of a great many diseases – including yellow fever and dengue fever – and viral infections like Chikungunya and Zika – it wreaks havoc on the most fragile and city-dwelling populations. A few degrees more and the threat of malaria will loom large over millions more people, not to mention diarrhoeal diseases which are often caused by water contamination. Closer to home for us – when it comes to the influenza epidemic, mild winters can bring about the development of variants and variations in herd immunity. In addition, the increase in temperature might well do what it has already done in the tropics: lengthen the influenza “season”, allowing the virus to mutate and develop more resilient strains.
Global warming is primarily caused by the burning of fossil fuels (gas, petrochemical oil, coal) on which we are all so dependant. In the medium term, we will have to face the serious and inevitable consequences. The only solution: to do things differently to slow the uncontrollable pace of these changes and rein in global warming.