The 6th IPCC report detailed

The 6th IPCC report, to be published in 2021 (final version of the first group’s work), is divided into several working groups:

  • “IPCC Working Group I (GWI) examines the physical sciences underlying past, present and future climate change.”
  • Working Group II (GWII) assesses the vulnerability of socio-economic and natural systems to climate change, the negative and positive consequences of climate change, and options for adapting to them.”
  • Working Group III (GW III) focuses on climate change mitigation, the evaluation of methods to reduce greenhouse gas emissions and the removal of greenhouse gases from the atmosphere.”

Chapters 1 and 2 deal with the reality and human (anthropogenic) origin of climate disruption and its consequences. They have already been dealt with by many people, and are not a priority for the purpose of Discover The Greentech, which is above all to study solutions. We’ll present them in a short paragraph. On the other hand, the conclusions of the third group will be discussed in detail.

[I had done this work based on the Technical Summary published in 2021. I’m now starting again with the final publication, digging into the complete document. I’ve made a dedicated page for each topic that has been the subject of such in-depth study]

Working groups 1 and 2: the physical reality behind climate change

[In progress. This will be a short summary. These chapters have already been covered by many, so I won’t go into too much detail]

Working group 3: decarbonizing the economy in practice

Group 3 of the latest IPCC report provides information on responses to climate change. In particular, it tells us that several measures could radically reduce greenhouse gas emissions for less than $20/tonne of CO2 avoided: decarbonization of electricity (wind, solar, nuclear), efficiency measures (methane leaks, buildings, lighting, etc.) and societal changes (telecommuting, development of cycling, etc.).

I’m going to concentrate here on two sets. On the one hand, the technical summary, which is very concise, to which I will refer with the following notation: TS, p.xx (TS= Technical Summary).


GHG emissions rose from 2.1% a year between 2000 and 2009 to 1.3% between 2010 and 2019. In 2019, they reached 59GTCO2eq, including 45 for CO2, 11 for methane, 2.7 for nitrous oxide (N2O) and 1.4 for fluorinated gases.

Emissions reductions in developed countries have not offset the global increase in population, electricity and heating demand.

Globally, GDP per capita and population growth would have been the main drivers of the increase in CO2 from fossil fuel combustion in the last decade [Rq: this assertion seems disctutable, as GDP was only an artificial indicator, not an agent, which is moreover admitted by the following, which evokes the GDP/CO2 decoupling], representing an annual increase of respectively 2.3and 1.2% respectively, which exceeds the reduction in energy use per unit of GDP (-2%/year) and energy carbon intensity (-0.3%/year). There has been a decoupling between CO2 (based on consumption) and GDP for some countries with high GDP/person. However, the 10 households with the highest incomes account for between 36 and 45% of GHG emissions. (TS, p.60)

Agriculture, forestry and other land uses1322%
TS p.65
Production of greenhouse gases (GHG) in Gigatons CO2eq by sector

If we include emissions linked to heat and electricity (= energy), transport, industry and buildings account for 66% of emissions (compared with 44% otherwise).

Forest cover has increased overall since 2010. However, deforestation in the Amazon has accelerated since 2016.

Households with incomes in the top 10% contribute between 36 and 45% of global GHG emissions. Two-thirds of them live in developed countries and one-third in developing countries.

Possible solutions

The IPCC has evaluated 8 trajectories (C1 to C8) of GHG evolution for which the global climate warms up to 4.2°C. (TS-42) C1 and C2 remain below 1.5°C in 2100, and C3 and C4 below 2°C. To limit global warming to 1.5°C, we need to release no more than 510 GtCO2eq, and 890 to stay probably below 2°C.

To achieve warming of 1.5°C, the trajectory envisages an increase in forest cover of 322 Mn ha by 2050. The amount of land dedicated to biomass production is 199 (56-482) million ha in 2100. Nevertheless, “the use of bioenergy can increase or reduce emissions, depending on the scale of deployment, the conversion technology, the fuel replaced and the location and method of biomass production.” There should also be a share of direct carbon removal(Carbon Dioxide Removal, CDR): afforestation and direct CO2 capture. (TS-47)

Chapters 6 to 12 of the final report assess recent advances in the various sectors. Overall, solutions representing a cost of less than $20 per tonne of CO2 avoided account for more than half of the economy’s decarbonization potential. (TS-107) The overall summary is at the end of the article.


In effective cost paths, the energy sector reaches “net zero CO2” before the rest of the economy. (TS-46) For scenarios C1 to C4, net energy emissions fall by 38-52n 2030 and 87% to 97n 2050. Electricity rises from 20 e the energy used in 2019 to 48-58 e the final energy in 2050.

Between 2015 and 2020, photovoltaic and wind electricity prices fell by 56t 45t and battery prices by 64% respectively. The reduction is even more dramatic when compared with the 2000s: the price of photovoltaics has been divided by around 10 and that of onshore wind power by 2 or 3. The price of batteries has been divided by 10 since 2010. Note that the price of offshore wind power is similar to that of the 2000s. (TS, p.67;

Between 2015 and 2019, photovoltaic power generation increased by 170%, reaching 680TWh, and wind power increased by 70%, reaching 1420 TWh. Nuclear power increased by 9t to 2790TWh. Hydroelectric power increased by 10%, reaching 4290 TWh. Overall, these energies accounted for 37 e of the electricity generated in 2019.

The emissions that can be anticipated with current infrastructures are 660GtCO2eq or, including infrastructures under design, 850, which is incompatible with the C1-C4 trajectories. (TS-26) To make it compatible without carbon capture (CCUS), fossil-fired power plants would have to be retired between 17 and 23 years before the end of their lifetime. (TS-53)

To decarbonize uses that direct electricity use cannot address, energy carriers will be needed, such ashydrogen, ammonia or low-carbon hydrocarbons (biogenic or synthetic). If the principle is that unprocessed electricity is the preferred option, hydrogen is particularly interesting for storing renewable energy. The efficiency of the “electricity-to-hydrogen-to-electricity” cycle could reach 50n 2030 [rq: it is ajd of 25%]. (TS-55)

Multiple energy supply options are available to reduce emissions over the next decade. (high confidence) Nuclear power and hydropower are established technologies. Solar photovoltaics and wind power are now cheaper than fossil fuel electricity in many places. Bioenergy accounts for around a tenth of the world’s primary energy. Carbon capture is widely used in the oil and gas industry, with early applications in power generation and biofuels. It will not be possible to widely deploy all these and other options without efforts to address the geophysical, environmental-ecological, economic, technological, socio-cultural and institutional factors that can facilitate or hinder their implementation. (high confidence)

Translated from the English, TS-56

Urban planning

The IPCC seems to favor urban concentration:

Although urbanization is a global trend often associated with rising incomes and increased consumption, the increasing concentration of people and activities allows for greater resource efficiency and large-scale decarbonization (very high confidence).

IPCC 2021, TS-61

Urbanization could triple between 2015 and 2050. The construction of new urban infrastructures could represent, with current practices, 8.5 to 14 GtCO2 annually until 2030 and double the need for materials from 40 billion tonnes per year in 2010 to 90 billion in 2050. (TS-65) Urban areas already account for between 67 and 72 of CO2 and CH4 emissions in 2020 (28GtCO2eq), through the production and consumption of goods and services. This could rise to 34 to 65 GtCO2eq by 2050. (TS-61)


Transport accounted for 5 GtCO2eq in 1990 and 8.7 GtCO2eq in 2019. It accounts for 23 of the CO2 emissions linked to energy production. 70% comes from land vehicles, 12 from aviation, 11 from ships and 1 from trains. Electric vehicles produce fewer greenhouse gases over their lifecycle than their combustion equivalents if they use low-carbon electricity (TS-67)

Electrification will play the central role for land transport, and biofuels and hydrogen [we talk about hydrogen mobility] will be able to play a role in decarbonizing freight in certain contexts. They are expected to be prominent in naval transport and aviation. (TS-68)

Theelectrification of public transport services has been shown to be a feasible, scalable and affordable mitigation option for decarbonizing mass transport. Electric vehicles are the fastest-growing segment of the automotive industry, having reached double-digit market share by 2020 in many countries. When charged withlow-carbon electricity, these vehicles can significantly reduce emissions.

One of the difficulties will be lithium extraction and the associated risks: availability of the resource, of course, but also the condition of workers and the local ecological impact.


Buildings accounted for 12 GtCO2eq in 2019, or 21 u total. 57% (6.8 GtCO2eq) was due to the external generation of electricity and heat, 24% (2.9 GtCO2eq) was produced on site, and 18% (2.2 GtCO2eq ) was due to the production of cement and steel required for their construction. Overall demand represented 128 EJ in 2019, 43 of which was electricity.

Solutions are divided into three areas: Sufficiency, Efficiency and Renewability (SER).

  • Sufficiency measures (Sufficiency, m²/person) to limit the demand for energy and materials over the long-term life of buildings. For example, we need to design buildings that are dense, compact and bioclimatic (?), encourage the circular use of materials, adapt housing to changing household needs, optimize the use of buildings through lifestyle changes, and so on. This type of measure could reduce the sector’s emissions by 17% by 2050. What’s more, these changes would be profitable for those implementing them.
  • Efficiency measures (EJ/m²) are the continuous improvement of technologies. They could reduce emissions by 30% by 2050.
  • Renewable” measures (MtCO2/EJ) could reduce emissions by 43% by 2050.


Note that the issue of sufficiency seems to be the most problematic. Indeed, the IPCC projects a 22% reduction in GHGs from the sector with efficiency improvements and 23 with renewables. On the contrary, the topic of sufficiency would increase emissions by 38% under current dynamics. (TS-73)

These measures would reduce the cost of building construction and use, without reducing the well-being of occupants.


The possibility of decarbonizing most industrial processes has been demonstrated using technologies that includeelectricity andhydrogen as energy or feedstock, carbon capture and utilization technologies(CCUS) for remaining emissions, and innovation in the circularity of material flows. (TS-10) There are several ways of reducing the need for primary production: reducing demand, increasing efficiency and the circular economy.

Nevertheless, industrial emissions continue to rise. Total decarbonization will be difficult, especially as it will account for 24% of total emissions in 2019. If we include emissions linked to the energy it consumes (heat/electricity), this rises to 34%, making it the main GHG emitter. We’re using more and more materials per GDP point.

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One of the challenges will be plastic: it is derived from

One of the challenges will be plastic: it is derived from

One of the challenges will be plastic: it is derived from

One of the challenges will be plastic: it is derived from

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