On August 9, the IPCC published its 6th report. Let's try to see things more clearly, and to start, let's focus for a moment on the IPCC.

WHAT IS THE IPCC?

Here is what we can read on the organization's website:
“The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 to provide detailed assessments of the state of scientific knowledge , technical and socio-economic on climate change, its causes, its potential repercussions and coping strategies. »

In other words, the IPCC compiles, studies and evaluates the scientific press relating to climate to produce summaries, updated periodically. Its authors do not make recommendations, they do not give orders to decision-makers, they take stock of current knowledge and model scenarios, based on available data, to anticipate the climate future.

This time, the 234 authors – handpicked AND volunteers – combed through 14,000 publications to produce a first version of the report. This was shared with reviewers who were able to make 78,000 comments, all of which were taken into account to obtain the second version. The revised version, which runs to some 4,000 pages, as well as the technical summary and that intended for political decision-makers, was finally submitted to all the representatives of the IPCC member states, who validated it, line by line.

This “repeat” publication system minimizes the risk of error and indicates that the 195 nations represented have read and validated the conclusions of the report.
Finally, let us remember that this report is the fruit of the work of group 1 of the IPCC, which has three:

• Group 1 studies the physical functioning of the climate and models its evolution.
• Group 2 is interested in the vulnerability of our societies to climate change, by evaluating the positive and negative consequences they can have as well as the possibility of adapting to them.
• Group 3 evaluates existing solutions to reduce greenhouse gas emissions or otherwise mitigate climate change.

The reports of groups 2 and 3, which will complement the one that interests us today, will be published next February and March respectively. A summary of the 3 reports is due to be published in September 2022.

OVERVIEW

Here are some key points to remember about the current state of the climate:

• It is indisputable that human activities are the cause of climate change.
• Recent climate changes, whether affecting the atmosphere, oceans, cryosphere or biosphere, are widespread, rapid and intensifying. They are unprecedented in thousands of years.
• Global warming makes extreme events, including heat waves, heavy precipitation and droughts, more frequent and more severe.
• The increase in surface temperature accelerates the rise of sea levels and causes warming, loss of oxygen and acidification of the oceans.
• Unless there is an immediate, rapid and large-scale reduction in greenhouse gas emissions, limiting warming to 1.5°C will be out of reach.

EACH ADDITIONAL TON OF CO2 RELEASE INTO THE ATMOSPHERE INCREASES WARMING

Warming is almost proportional to cumulative CO2 emissions into the atmosphere.
If each ton of CO2 released amplifies warming, by contrast, all avoided emissions reduce warming. Let's open a digression to explain what the 5 scenarios retained by the IPCC in this report correspond to:

• SP1-1.9
• SSP1-2.6
• SSP2-4.5
• SSP3-7.0
• SSP5-8.5

Let's take the SSP2-4.5 scenario as an example.

SSP stands for Shared Socio-economic Pathway and designates a scenario which takes into account several parameters such as the evolution of the world population, the pace of growth or the degree of international cooperation in the face of the climate emergency.
SSP2 therefore refers to a defined socio-economic scenario, nicknamed “the middle way”. To find out the details of the five scenarios, go to the corresponding Wikipedia page. 4.5 designates the level of radiative forcing associated with the SSP2 scenario. This notion, which is essential to fully understand the phenomenon of global warming, is explained very clearly by Le bon pote here. Today the radiative forcing is 2.3 W/m². Remember that it increases each time CO2 is emitted and stored in the atmosphere. And the more it increases, the more the temperature on the surface of the globe increases.

To put it simply, the SSP1-1.9 scenario corresponds to the best of all worlds, in which the energy transition would take place at high speed, in a concerted manner at the national and international levels; the SSP5-8.5 scenario models the disaster scenario, with galloping growth, increased use of fossil fuels and no measures taken to reduce emissions. Both are equally improbable.

For the moment we are rather following the yellow curve, SSP2-4.5, which leads to an increase of 2°C around 2050, and of 2.7°C by 2100.

CLIMATE CHANGE ALREADY AFFECTS ALL INHABITED REGIONS OF THE PLANET

Extreme heatwaves will increase throughout the world, with a high degree of certainty in most cases.
Intense precipitation will increase in some regions while droughts will gain ground in others. However, these forecasts are less reliable, due to a lack of consensus or a limited data panel.

WARMING AMPLIFIES EXTREME CLIMATIC PHENOMENA (HEAT WAVES, HEAVY PRECIPITATION, DROUGHTS, CYCLONES)

If we take the example of heatwaves occurring once every ten years before the industrial era, we observe that today, due to an increase of 1°C in the average temperature, they will occur probably 2.8 times per decade.
If warming reaches 2°C, they will occur on average 5.6 times per decade, and their intensity, which was around +1.2°C with a warming of 1°C, will increase to +2.6°C .

Intense precipitation and droughts will be subject to a comparable surge, although to a lesser extent.

What should we conclude from this?
Well, the more the average temperature increases on the surface of the globe, the more violent and frequent will be heatwaves, droughts, floods, precipitation... In other words, and as climatologist Christophe Cassou, author of the report, says: “Each fraction of a degree counts because it conditions the risk associated with extreme events. If we cannot contain global warming to +1.5°C, we must do everything to limit it to +1.6°C. »

CARBON BUDGETS

Since the publication of the first IPCC report in 1990, that is to say in thirty years, 1,000 billion tonnes of CO2 (GtCO2) have been emitted. This is almost half of our cumulative emissions (2,390 GtCO2) since the start of the industrial era in 1850.

Taking into account the almost proportional relationship between cumulative emissions and the increase in the average temperature on the surface of the globe, it is possible to calculate what margin we have left depending on a temperature objective to be achieved, or not to be achieved. exceed.

This is where carbon budgets come from.

Given that global emissions are currently around 40 GtCO2/year, this budget is likely to shrink dramatically, hence the rapid, widespread and sustained changes over time that the IPCC is urging policy makers to make.

CONCLUSION

“Unequivocally”: this formula is a big step for the IPCC. Man's responsibility is now demonstrated. Energy production, industry, transport, residential, tertiary, agriculture, waste treatment, all these sectors, because they emit greenhouse gases, contribute to warming the planet.

If the consequences of “business as usual” as described in this report – the red scenarios – send chills down our spines, the worst can still and must be avoided. To do this, it is about being aware of the threat that weighs, taking note of it and acting accordingly.

The avenues are known: energy efficiency of buildings, renewable energies, sustainable mobility, creation of carbon sinks... All of this contributes to the reduction of carbon dioxide emissions and therefore slows down global warming and mitigates its consequences.

The fact remains that ambitious public policies, massive investments, accountability of all economic actors, as well as effective collaboration on an international scale, will be all decisive factors for the success of the energy transition which is taking place. imposed.