The most important number of the climate crisis: 421.2
Atmospheric CO2 in parts per million, 19 February 2024
Source: NOAA via The Guardian
Causes of global heating
The Earth maintains a habitable temperature due to the ability of the Earth's atmosphere to reflect some of the heat (infrared radiation) from the sun back into space. The heat that reaches the Earth's surface is either absorbed or reflected upwards. The reflected heat either passes through the Earth's atmosphere into space or is reflected a second time back to Earth by certain gases in the atmosphere. This combination of receiving solar heat through the Earth's atmosphere and having some reflected back to Earth is called the Greenhouse Effect .
Without the greenhouse effect, the Earth would be a cold and hostile planet, and probably uninhabitable. Maintaining the correct balance of twice-radiated heat and heat escaping into space is essential to keeping the Earth’s temperature within a range that can support life as we know. It is a very fine balance that can easily be upset.
The greenhouse gases (GHG) comprise mainly carbon dioxide (CO2) and methane. They pose no harm when they occur naturally to maintain the right balance of radiated heat. However, when they are present in excess, the system becomes unbalanced, the ambient temperature increases and the climate starts to go awry.
When we burn organic* fuels, and when organic matter decomposes, carbon dioxide or methane is released into the air. These gases, which are additional to what Earth's natural processes produce, increase the total amount of greenhouse gases in the atmosphere. This in turn means that more heat is reflected back to Earth instead of passing through the atmosphere into space.
Our ever more industrialised society has pumped increasing amounts of greenhouse gases into the atmosphere, to the point where they are now having severe consequences for the climate and threatening most forms of life on Earth.
* "Organic" means "containing carbon atoms".
Code Red for all life on Earth
"Code Red for humanity" is the dire warning issued by António Guterres, UN Secretary General, following release of the UN's Intergovernmental Panel on Climate Change's (IPCC) 6th assessment report. But really it's Code Red for all life on our planet home.
The report says that major climate changes are inevitable and irreversible. Global temperature to 1.5 degrees C above pre-industrial levels by the early 2030s seems unavoidable. The most recent IPCC report ends by saying any further delay in climate action “will miss a brief and rapidly closing window of opportunity to secure a livable and sustainable future for all”.
We are already well into a global climate crisis, with many extreme weather events - heatwaves, droughts, storms and cyclones resulting in unprecedented wildfires, flooding, coastal erosion, and bleaching and death of coral reefs. These in turn cause devastating effects on human health and safety, economic and social wellbeing, and collapsing ecosystems.
The reports say we must cut our greenhouse gas emissions by at least 65% before 2030, and reach net zero emissions within 15 years, to avoid complete climate catastrophe.