Par Kenny Chicate-Moibert, André Naegely-Hofstetter, Florian Girardot, Maria Smetanina, Julien Brocard, Paul Frere, Manon Lombardet, étudiants ESTA Belfort, 05/2022
Mots clés: #IPCC #climate change #global warming
What is the IPCC?
The IPCC prepares a comprehensive assessment of the current state of scientific, technical and socioeconomic knowledge on climate change, its impacts and future risks, and options for reducing climate change. It also produces reports on issues agreed by member governments, as well as methodological reports that provide guidance for the preparation of greenhouse gas inventories. The IPCC is preparing the Sixth Assessment Report, which consists of three working group papers and a synthesis report. The WG1 contribution was completed in August 2021, and the WG2 contribution was completed in February 2022.
IPCC 1 group : Impact
Definition of the environmental impact, how to calculate it with the carbon footprint, how does the IPCC calculate it with their data (digging in their previous reports to find the most accurate parts and global stats that we can add in order to make our article the clearest it can be.
Give a brief first glance on how the IPCC predicts our future in the coming years (the 5 different scenarios regarding the climate in the coming years), so that we can develop each single scenario individually afterwards.
Current climate conditions and the IPCC Scénarios
Current climate conditions
There is no doubt that human influence has warmed the atmosphere, ocean and land. Rapid and significant changes have occurred in the atmosphere, ocean, cryosphere and biosphere.
100% of global warming is due to human activity. This is a certain and unequivocal fact (to understand what radiative forcing is, read this article).
The magnitude of recent changes in the overall climate system and the current state of many aspects of the climate system are unprecedented, ranging from hundreds to thousands of years.
Over the past three thousand years, sea level has not risen as rapidly as it has since 1900
Since the first IPCC report was published in 1990, 1,000 billion tons of carbon dioxide have been emitted. That’s almost half of our emissions since the beginning of the entire industrial era.
Human activity is warming the climate at a rate not seen in at least 2,000 years. Recent climate change has been widespread, rapid and intensified. Compared to 1850-1900, temperatures have increased by 1.1°C in the last 10 years.
Human-induced climate change has affected many extreme weather and climate events in all regions of the world. Evidence of changes in extreme events such as heat waves, heavy rainfall, droughts, and tropical cyclones, especially their attribution to human influence, has increased since AR5.
We will develop the different scenarios.
The IPCC Scénarios (Intergovernmental Panel on Climate Change)
SSP1-1.9 : The addition of the CO2 concentration in the atmosphere of from -18 Gita Tons of CO2 per year, -9 Megatons of Methane per year, 8 Megatons of Nitrous oxide per year and 4 Megatons of Sulphur dioxide per year will lead to a global surface temperature increase from 1,2°C to 1,9°C
SSP1-2.6 : The addition of the CO2 concentration in the atmosphere of from -9 Gita Tons of CO2 per year, -9 Megatons of Methane per year, 8 Megatons of Nitrous oxide per year and 4 Megatons of Sulphur dioxide per year will lead to a global surface temperature increase from 1,4°C to 2,6°C
SSP2-4.5 : The addition of the CO2 concentration in the atmosphere of from 5 Gita Tons of CO2 per year, 8 Mega Tons of Methane per year, 240 Megatons of Nitrous oxide per year and 31 Megatons of Sulphur dioxide per year will lead to a global surface temperature increase from 2°C to 3,5°C
SSP3-7.0 : The addition of the CO2 concentration in the atmosphere of from 82 Gita Tons of CO2 per year, 790 Mega Tons of Methane per year, 21 Megatons of Nitrous oxide per year and 79 Megatons of Sulphur dioxide per year will lead to a global surface temperature increase from 2,6°C to 4,6°C
SSP5-8.5 : The addition of the CO2 concentration in the atmosphere of from 125 Gita Tons of CO2 per year, 490 Mega Tons of Methane per year, 16 Megatons of Nitrous oxide per year and 35 Megatons of Sulphur dioxide per year will lead to a global surface temperature increase from 3,2°C to 5,7°C
Average estimations from the following graphics :
From IPCC’s AR6 WGI full report
The IPCC’s Average estimations of temperatures evolution on Near term, Mid-term and Long-terme :
Near-term : 2021 – 2040
Mid-term : 2041 – 2060
Long-term : 2081 – 2100
From the best estimation to the worst one.
Note : Best estimation is the average temperature between the best one and the worst one.
All SSP scenarios predict that the Earth will warm by 1.5°C. The most ambitious emission projections predict that we will reach 1.5°C in the 2030s, then peak at +1.6°C, before falling back to 1.4°C by the end of the century.
The problem is that we know that the technology needed to achieve negative emissions at these orders of magnitude does not exist or has never been tested at this scale.
Information on future climate change and its consequences
Under scenarios of increasing CO2 emissions, oceanic and terrestrial carbon sinks will be less effective in slowing the accumulation of CO2 in the atmosphere
The IPCC describes the evolution of future temperatures according to 5 different socio-economic pathways (SSP)
In all emission scenarios (except the lowest one, SSP1-1.9), we will exceed the global warming threshold of +1.5°C in the near future (between 2021 and 2040) and remain above +1.5°C until the end of the century.
With continued warming, each region could experience more extreme weather events, sometimes in combination, and with multiple consequences. This is more likely to happen with +2°C warming than 1.5°C (and even more so with additional warming levels). Translate « combined » as « several at once » (heatwave, followed by megafires for example, as in Canada in June 2021).
Tipping points are included in the report because, although they have a lower probability of occurring, they could have devastating consequences. Low-probability events, such as ice sheet melt, abrupt changes in ocean currents (e.g., AMOC), some cumulative extreme events, and warming significantly greater than the range of warming estimated to be very likely, cannot be excluded and are included in the risk assessment.
The glaciers in the mountains and at the poles are doomed to melt for decades or even centuries to come, while the release of carbon from the permafrost by thawing, considered over a period of more than 1000 years, is irreversible.
Limiting climate change in the future
In order to limit global warming, strong, rapid and sustainable actions will be needed to reduce CO2, methane and other greenhouse gas emissions. This would not only reduce the consequences of climate change but also improve air quality.
Limiting global warming to +1.5°C will no longer be possible without an immediate and large-scale reduction of GHG emissions (see the different scenarios).
If we reach carbon neutrality, global warming should stop (with more certainty than in the previous report).
Many changes due to past and future greenhouse gas emissions are irreversible for centuries or even millennia, including changes in the oceans, ice caps, and global sea level. However, some changes can be slowed and some stopped by limiting global warming.
Estimates of the remaining carbon budget – a simplified way of assessing how much CO2 can be released before a given level of warming is reached – have been improved since previous reports, but the carbon budget remains broadly unchanged.
Change projection :
Projected changes are shown at global warming levels of 1°C, 1.5°C, 2°C, and 4°C and are relative to 1850-1900 representing a climate without human influence. The figure depicts frequencies and increases in intensity of 10-year or 50-year extreme events from the base period (1850-1900) under different global warming levels. (Too change and explain properly)
Attribution of extreme events
Very significant progress has been made since the last IPCC attribution report. It is science that tells us whether we can attribute extreme weather events to climate change. Here is what the IPCC told us:
« Human-induced climate change has affected many extreme weather and climate events in all regions of the world. Since AR5, evidence of changes in extreme events such as heat waves, heavy rainfall, droughts, and tropical cyclones, particularly their impact on the attribution of human influence, has been strengthened. »
The global proportion of major tropical cyclones (categories 3 to 5) may have increased over the past four years.
It is no longer necessary to talk about the effects of climate change on all events in general; for example, we can estimate how much human activity has exacerbated a given heat wave (see also the work on global weather attribution)
The IPCC is the first to describe the observed increase in extreme hurricanes. Previously, these changes were too uncertain to have international consensus. Extreme weather events are now becoming more severe in all regions of all continents (with the exception of southern South America, where data is too sparse).
Here is an excellent infographic that expresses the probability of different extreme events based on possible warming:
Regionality of climate change
The IPCC also points out that « natural factors and internal variability will moderate anthropogenic changes, particularly on a regional scale and in the short term, with little effect on centennial climate warming ». These adjustments are important when planning for any possible changes, especially for risk management.
Based on the 2 temperatures proposed by the IPCC (+2°C and +4°C), it is clear how differently things are warming on Earth.
The second diagram shows the rise in water levels caused by global warming. We therefore notice that the more the climate changes, the more the consequences on our lives (rising sea levels, temperature increases) the more difficult our living conditions will be.
Proportion of CO2 emissions
The graph above shows the division of CO2 emissions between 3 different spaces (ocean, land, atmosphere) according to the 5 scenarios from 1850 to 2100. From this graph, we can observe that it is in the atmosphere that global warming will have the most impact. Indeed, it is in the atmosphere that there is the biggest difference according to the scenarios. However, we must not forget that the oceans and the land will also be affected by these changes.
Global surface temperature changes in °C (referral : 1850-1900)
In all scenarios the global temperature increases however we observe a high delta (about 3.5°C).
Arctic ice evolution and projections in 10^6 km²
The global warming of the surface temperature leads to a melting of the ice. From the graph above, we can see that the ice melt is important. In 3 of the 5 scenarios, we can see that by 2100 we will be below the practically ice-free limit.
Sea level increasing projections in metters
Due to global warming and melting ice, the sea level is rising between 0.2 and 0.7 metters depending on the different scenarios until 2100.
Ocean acidity (pH) projections
This graph shows us that the ocean acidity increase more and more strongly according to the different scenarios.
Synthesis and conclusion
According to climate scientists, our world is likely to continue to warm this century and beyond. The conclusion is based on scientists’ understanding of how the climate system works and computer models developed to simulate Earth’s climate. Results from various climate model simulations suggest that Earth’s average temperature in 2100 could be 1.1 to 5.4°C (2 to 9.7°F) warmer than it is today.
The main cause of the temperature increase is carbon dioxide and other heat-trapping « greenhouse gases » produced by human activities. The biggest source of extra carbon dioxide is people burning coal and other fossil fuels.
The exact amount of warming that will occur in the coming century depends largely on the energy choices that we make now and in the next few decades, particularly since those choices directly influence how fast we put heat-trapping gases into the atmosphere. And so we have to take care about the different consequences of this warming. These risks include sea level rise, leading to coastal flooding and erosion; changes to the salinity of coastal groundwater supplies, resulting in freshwater stress; risks to marine ecosystems, such as mass coral bleaching and die-offs; and more intense tropical cyclones. Limiting warming to 1.5 degrees Celsius will mean 40,000 less people will see their land inundated by 2150.
IPCC AR6 WG (2021), Climate Change 2021 The Physical Science Basis, available from: https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Full_Report.pdf
Thank you for this article about IPCC Climate report !
You talk aout limitate global warming/climate change in the future, but how can we do that to avoid SSP5 ?
What are concrete actions that we/the society can do to limitate global warming ? It less consumption or are there other concrete actions?
Thank you in advance for your answer.
We can all act at our own level to fight against global warming
We can for example use more transport, consume less meat, choose local food…
To limit global warming we have to change our lifestyle.
Bravo for this quality article! Everything is very well explained and even if it doesn’t reassure much, you at least state the truth.
However, I had a question about the carbon neutrality you discuss in your article. You say that if we achieve carbon neutrality, global warming should stop. Do you really think we can achieve a balance between carbon emissions and carbon absorption from the atmosphere by carbon sinks when the world’s population is growing? This means more energy production and consumption to satisfy all these people and consequently a lot of GHG emissions.
Thank you for your comment Léonore. I think to answer your question we should change the mentality of people. I think people should limit their consumption. This could solve a lot of problems in my opinion.
Hello Leonore, thank you for your comment. The answer you received from Julien was clear but I think that we have to highlight something else : we have to understand that when we are talking about « people » we are also talking about the entity composed by those « people ». For example governments and companies could have a big impact if they involve themselves to this challenge. We have to do it all together, that’s the only way to achieve it !
First I would like to congrats you for this wonderful job you did on summarizing the IPCC Climate report ! Your article was really pleasant to read and well illustrated, however, I would have liked to see more illustrations in the introduction !
Also I was looking at the different scenario the IPCC Climate report identified and I was wondering which one is the most likely to happen. In my opinion, it is scenario SSP2-4.5, even though it is not the most favorable it is the most realistic.
You may have a better understanding of the subject so in your opinion which scenario is the most likely to happen as of today ?
Thank you Alessio for your comment and we will take note to better illustrate our next publication.
In my opinion, this is also the most realistic SSP2-4.5 scenario, even if it is not the most favourable. Nevertheless I do not exclude scenario 1. I really hope that this is what will happen because it would allow us to live in a better world. But for that to happen, as I answered Leonore earlier, we would have to change our mentalities to allow us to limit consumption.
I have a question for you, but first of all I would like to congratulate you for your rewarding article. It is clear, concise and it contains all the information necessary about the five IPCC’s scenarios.
In your article you say we need to reach carbon neutrality to stop global warming. But what are the concrete solutions to reach it ? You are not mentionning that and I would like to know if there are any possibilities !
This article was very clear and interesting!
We should be more aware about the impact of global warming!
I wonder what would happen in a doomsday scenario where the temperature would rise by almost 10°C? If you have a hypothesis for this scenario I would be glad to hear it!
And cool video by the way !!!
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