What are greenhouse gases?
Like in a greenhouse, greenhouse gases are gases that keep the heat from earth from escaping to space, thus resulting in the warming up of the global temperature in the air and oceans.
Why is the warming up of Earth's temperature a problem?
By warming up the atmosphere and the oceans, the ice is melting, making the ocean rise from a few meter. Because of this, entire coastal cities like New-York will be wiped off the map. The change in temperature changes the climate equilibrium, which has for consequences in some part of the world heavy floods, and in other parts droughts. These extreme climate events will cause food production yields to drop, famine, diseases, and therefore a massive mortality rate and mass migration.
These extreme conditions will also have massive consequences on the economy, with a major crisis, millions of persons losing jobs.
Carbon budget and 2 degree goal
The raise of the temperature is directly linked to the concentration of greenhouse gases in the atmosphere. The highest the concentration, the highest the raise of the temperature.
In the Paris Agreement signed in 2016, 195 from 197 countries of the United Nations agreed to keep the increase in global average temperature to "well below 2 °C above pre-industrial levels; and to pursue efforts to limit the increase to 1.5 °C".
To have a 50% probability to stay below 2°C, their should be a maximum concentration of 545 ppm (parts per million) of greenhouse gases, or 478 ppm to have a 50% of chance to stay below the 1.5 °C limit.
In 2016, the concentration of greenhouse gases was already 449 ppm, with an annual increase of about 4 ppm/year.
Which gives a left "budget" of about 63 ppm. With an increase of about 4 ppm/year, this budget will be completely used within 15 years.
Who are the main contributors to greenhouse gases?
Contributors to greenhouse gases since 1751
By calculating all the CO2 that has been emitted since 1751 by each country in the atmosphere, we can determine who has contributed most to global CO2 emissions.
The first contributor being Europe (including Russia) with 33% of global emissions, then North America and Asia tied for second (29% each).
Contributors to greenhouse gases today (2017)
If we look at the same graph today, the picture looks however quite different. Today, more than half of the CO2 emissions come from Asia.
However these emissions are the one produced in the country itself. Has most of the world production has been sent to Asia, each country that has production units there, should also be accounted for these emissions in Asia.
Where do greenhouse gases come from?
The main greenhouse gases are:
Carbon dioxide (CO2) - 76% of all greenhouse gases CO2 is mainly produced while burning fuel, which produces energy (heat, electricity) used in every sectors: transport, industry, agriculture, residential, commercial.
Methane (CH4) - 17% of all greenhouse gases The main source of methane is the agriculture sector, and in particular meat production. Indeed, methane is produced by the digestive process of ruminant livestock (animals which regurgitates food and re-chews it).
Nitrous oxide (N2O) - 7% of all greenhouse gases N2O comes by 72% from agriculture. The main reason for it being the use of synthetic fertilizer to grow crops.
Therefore one quarter of all greenhouse gases comes from agriculture. From livestock on one hand and from synthetic fertilizers on the other hand.
What is the distribution of CO2 emissions from fuel combustion among the different sectors?
As shown on this graph, the four main sources of greenhouse gases emissions are:
Electricity and heat production (49%) Emissions from public heat and electricity production.
Transport (20%) All transport activity, regardless of the sector. This includes domestic aviation, domestic navigation, road, rail and pipeline transport. International marine bunkers and international aviation are not included.
Manufacturing industries & constructions (20%) Cement and aluminium play an important role here.
Residential buildings & commercial and public services (9%)
What can we do to act against climate change?
We have very much to do, and so little time. But if each and everyone of us, does as much as possible, as soon as possible, it might still be enough time to avoid the worst case.
Now, you might feel overwhelmed and ask yourself what you can do at your own scale? Well, way more than you actually think, and I will tell you what.