7 not-so-dumb questions about the latest IPCC report

7 not-so-dumb questions about the latest IPCC report

Our summary of the first part of the latest IPCC synthesis report on climate change.

Patrick Nollet

Patrick Nollet



🤔 What is this IPCC report that everyone is talking about?

👉 This is the first part of the new IPCC report (the previous synthesis report was from 2014), describing our understanding of climate change, its causes as well as its physical consequences. Two other parts will be published by the end of 2022: the second will focus on the implications for biodiversity and human societies as well as adaptation solutions, and the third will describe the state of the art of solutions to limit emissions and envisage a sustainable future.

🤔 But the IPCC are ideological ecologists, right?

👉 Non : Le rapport est scientifiquement inattaquable. Un travail immense a été réalisé (234 auteurs, 14000 références…). C’est une synthèse exemplaire de la littérature scientifique existante qui permet de dégager un vrai consensus scientifique. Chaque affirmation du rapport est soigneusement pondérée par la confiance qu’ont les auteurs par rapport à cette affirmation (« it is {likely / very likely / extremely likely} that… »). On peut donc lui faire confiance. Ce rapport va bien au-delà des logiques partisanes.

🤔 Is there still any doubt about the human influence on climate change?

No: One of the first sentences of the report sets the tone: "It is unequivocal that human influence has warmed the atmosphere, ocean and land. And this is not simply the acceleration of a natural process: the average temperature increases almost linearly with the amount of CO2 emitted by humans. We have entered the warmest period in over 100 000 years, and the trend is not about to be reversed.

Temperatures have risen significantly since the industrial era - IPCC

🤔 What are the expected consequences?

👉 The first obvious consequence of climate disruption is a rise in average temperatures. Several scenarios are envisaged depending on the evolution of greenhouse gas emissions, ranging from +1.4°C to +4.4°C in 2100 compared to the pre-industrial period. But beware: these are only average values. This increase is not uniform across regions. In particular, temperature increases in continental and polar areas will be much higher. Furthermore, heat waves are likely to intensify. We will have to wait for the second part of the report to get an idea of the consequences of these changes on our societies, but it is already clear that the changes will be so radical in some regions that we cannot simply say that "man will adapt".

Other consequences include a rise in sea levels of between 0.5 and 1 metre by 2100, depending on the scenario. And if we look ahead to 2300, the rise could be as much as 7 metres, or even 15 metres in a scenario that cannot be ruled out. I'll let you imagine the consequences. At 7 metres, the island of Noirmoutier has practically disappeared, and only the centre of the town of Arles is still emerged. And in some countries, the situation will be dramatic.

It should also be noted that global warming is accelerating the water cycle, which will increase rainfall in many areas. But again, the consequences have to be studied precisely region by region, because in other areas it is the droughts that will intensify.

🤔 But I had a rotten summer! I don't believe in all that.

👉 And yet: the case of France in July and August 2021 is very particular, due to an exceptional meteorological phenomenon of cold drop. All around us, heat waves have indeed occurred. There are even fears of a pasta shortage due to the heat wave in Canada and the floods in Europe that have put a strain on global durum wheat production.

Furthermore, the IPCC report reminds us that temperature variability over a decade is significant. So beware of false impressions, and let's keep an eye on general trends and the common good.

🤔 Is it still possible to reverse the trend?

Yes and no. The culprits are known. They are mainly carbon dioxide, methane and nitrous oxide emissions. Since the correlation between global warming and these emissions is known, it is easy to deduce a carbon budget that should not be exceeded depending on the scenario we wish to commit to.

So we know what we have to do: work to reduce these emissions in our activities. First of all, we need to raise our collective awareness. Then, it is up to each individual or industry to work on reducing their own emissions by implementing the following triptych:

1. Measure (Collect all the data needed to accurately calculate our carbon emissions)
2. Analyse (Identify the most important sources of emissions)
3. Act (Implement and monitor an action plan to reduce emissions).

However, if we can limit the extent of climate change, basic trends have already begun and are irreversible, particularly in the oceans (temperature rise, acidification, deoxygenation, etc.). Thus, whatever we do, the ice cap will continue to melt for centuries or even millennia, and sea levels will continue to rise. All we can do today is limit the damage. And that's already a lot!

🤔O kay, fine. I need to find out more. How do I do that?

👉 No way to read the full report (3,949 pages!), which should be seen as encyclopaedic content. Many summaries are available. The 42-page summary published by the IPCC is a bit technical but still readable if you have a good command of English. It contains many graphs and figures. If you only have five minutes to spare, at least read their 2-page super-summary. Among the French sources, special mention to BonPote who made a summary accessible to all.

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