Qui réchauffe le climat (et comment) ? Ft. Le Réveilleur — Transcript

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1. 0:02"It is unequivocal that human influence has warmed the atmosphere ocean and land"
2. 0:08That is a quote from the 1st part of the 6th IPCC report,
3. 0:11a scientific work that describes the physical manifestations
4. 0:15of climate change and reaffirms the responsibility of human activities.
5. 0:21The 2nd part outlines the past, present,
6. 0:23and future consequences of climate change,
7. 0:27and the 3rd details how to reduce greenhouse gas emissions,
8. 0:31which are the primary cause of this climate change.
9. 0:35But what are these greenhouse gases? Who is emitting them?
10. 0:39And how?
11. 0:41That's what we're going to look at in this video because we need to know
12. 0:44the answers to these questions in order to act on these emissions.
13. 0:51Among the greenhouse gases, whose emissions by human societies
14. 0:55affect the climate, are carbon dioxide, methane,
15. 0:58nitrous oxide and fluorinated gases,
16. 1:02which are a group of many molecules containing
17. 1:05one or more fluorine atoms.
18. 1:08Because of their physical differences, these gases have different effects.
19. 1:13First, they warm the planet differently.
20. 1:17Secondly, depending on the gas, the excess added by our emissions
21. 1:21to the atmosphere will take more or less time to be eliminated.
22. 1:25Fortunately, there is a tool to compare
23. 1:27and aggregate the emissions of different greenhouse gases.
24. 1:32The Global Warming Potential (GWP) allows us to convert a quantity
25. 1:36of a gas into its CO2 equivalent.
26. 1:44Let's take methane as an example.
27. 1:47This factor indicates how many kilos of CO2 would be needed to produce
28. 1:51the same warming as 1 kg of methane over a given period of time.
29. 1:56That's right.
30. 1:56Because of the difference in the lifespan of these gases,
31. 1:59we have to define the period considered in order to make a comparison.
32. 2:04If we consider the 20 years following the emission,
33. 2:061 kg of methane is equivalent to 81 kg of CO2.
34. 2:10But if we consider the century following the emission,
35. 2:141 kg of methane is equivalent to 28 kg of CO2.
36. 2:17And if we consider 500 years, we drop to 8 kg of CO2 equivalent.
37. 2:23The further into the future we consider the effects,
38. 2:26the less important methane is compared to CO2.
39. 2:29Within the framework of the international climate negotiations,
40. 2:32the convention has been set at 1 century.
41. 2:34This is the convention that will be used for the rest of the video,
42. 2:38and it is the one that is generally used for quantifying equivalents in CO2.
43. 2:45If we stop here, we may get the impression that methane plays
44. 2:49a greater role in climate change than CO2.
45. 2:51But we're looking at an effect per kilogram, so you have to multiply that by the amounts
46. 2:56emitted.
47. 2:58In 2019, methane emissions from human societies
48. 3:02were about 400 M tons
49. 3:05and CO2 emissions were over 40 bn tons.
50. 3:09With the global warming potential defined earlier,
51. 3:12we can convert methane emissions into a CO2 equivalent.
52. 3:17This allows us to aggregate these two gases.
53. 3:20We can do the same work for the other greenhouse gases
54. 3:23and integrate them into this representation.
55. 3:26In 2019, fluorinated gases will account for 2%
56. 3:31of total global emissions in CO2 equivalent,
57. 3:33nitrous oxide for 4%,
58. 3:37methane for 18% and CO2 for 75%.
59. 3:48We now know what these gases are. But where do they come from?
60. 3:53Let's focus first on CO2 emissions. We can trace them from 1850 on.
61. 4:00The annual amount of CO2 emitted by human societies has increased
62. 4:05from decade to decade.
63. 4:07These emissions can be separated into 2 categories.
64. 4:11First, the emissions from what is called land-use change.
65. 4:16These are the CO2 emissions and removals from human-managed land.
66. 4:21For example, the CO2 emissions from a forest that would
67. 4:24be destroyed to make a field instead.
68. 4:28At the global level, you can see that the net effect
69. 4:31is an emission of CO2, notably because of deforestation.
70. 4:36Then there are the emissions from industrial processes and especially
71. 4:40from the combustion of fossil fuels.
72. 4:43They have increased very quickly since 1950.
73. 4:46They can be divided into different sub-categories.
74. 4:50Coal remains the fossil resource whose combustion adds the most CO2
75. 4:54to the atmosphere each year,
76. 4:57followed by oil and then fossil gas, a more accurate name than natural gas.
77. 5:03We can also note cement, the production of which directly emits CO2.
78. 5:08These annual CO2 emissions are added to the atmosphere.
79. 5:13As a result, the atmospheric concentration
80. 5:16of CO2 has only increased since the industrial revolution
81. 5:20and much more rapidly in the last few decades when emissions have been higher.
82. 5:24There is a direct and almost linear relationship
83. 5:27between this concentration and the rise in temperature.
84. 5:30So let's look at the cumulative CO2 emissions.
85. 5:34Between 1850 and 2019, human societies have added
86. 5:392,430 billion tons of CO2 to the atmosphere.
87. 5:44Which countries have emitted all this?
88. 5:51In order to answer more easily, we must first group them together.
89. 5:55Developed countries are separated into those in North America,
90. 5:58Europe and the rest of the world.
91. 6:01Then we have a group for all the rest of the Americas,
92. 6:02a group for the African countries and another for the Middle East.
93. 6:08The rest of Eurasia is divided into a group encompassing
94. 6:11Eastern Europe and part of Asia, East Asia, which includes China,
95. 6:15South Asia, which includes India,
96. 6:18and Southeast Asia, to which we add
97. 6:21the developing countries of the Pacific.
98. 6:25If we look at the cumulative CO2 emissions between 1850 and 2009,
99. 6:30in each of these groups, we get this.
100. 6:33Emissions from fossil resources
101. 6:35and industrial processes are shown in black
102. 6:39and those from land-use change in green.
103. 6:42We also see emissions from international air and sea transport,
104. 6:46which are conventionally counted separately.
105. 6:50With this historical approach, developed countries account
106. 6:53for nearly 45% of CO2 emissions.
107. 7:00The distribution of the historical accumulation is an important element,
108. 7:04but it does not tell us anything about the current distribution of emissions.
109. 7:08If we take all the greenhouse gases emitted in 2019,
110. 7:11we have 59 billion tons of CO2 equivalent.
111. 7:16If we divide these emissions between the groups we have defined,
112. 7:19we get this: East Asia, which includes China,
113. 7:23is responsible for a little more than 1/4 of the 2009 emissions
114. 7:26and dominates this representation.
115. 7:30This was not the case for the previous one.
116. 7:33But some of these groups are much more populated than others.
117. 7:37To take this aspect into account, we can divide the emissions
118. 7:40of the different groups by their population to obtain emissions per capita.
119. 7:45This changes the picture again.
120. 7:48We see, for example, that per capita emissions
121. 7:50are more than 7 times higher in North America than in South Asia.
122. 7:55Now, let's give these columns a width
123. 7:57proportional to the population of the group.
124. 8:00For each group, the height of the rectangle
125. 8:03gives the per capita emissions and the width gives the population.
126. 8:07The per capita emissions for North America are 19 tons
127. 8:10of CO2 equivalent for 366 M people.
128. 8:16This representation allows us to see, for example, that South Asia,
129. 8:20a group containing India, has low per capita emissions,
130. 8:24but weighs about as much as Europe in the total emissions,
131. 8:26because it is a much more populated region.
132. 8:35These greenhouse gas emissions can be broken down into CO2 emissions
133. 8:40from fossil resources and industry, CO2 emissions from land-use change,
134. 8:45and emissions of other greenhouse gases.
135. 8:49Land-use change accounts for CO2 emissions and removals from land managed by humans.
136. 8:55In some regions, deforestation causes CO2 emissions,
137. 8:58but there are large variations.
138. 9:01In particular, we see the importance of deforestation
139. 9:04in Latin America and Southeast Asia.
140. 9:07In Europe and North America, there is slightly more absorption
141. 9:10than emission, partly because forests are expanding.
142. 9:16I can add one last subtlety, but we need to change the source of our data
143. 9:20and only consider CO2 emissions from fossil resources and industry.
144. 9:25If a phone is made in China, but used in Europe,
145. 9:28should we allocate the emissions from its manufacture to the country
146. 9:33of the producer or the consumer?
147. 9:36So far, we use a territorial approach
148. 9:39for this allocation.
149. 9:40This is the official way of doing it.
150. 9:42We attribute the emissions to the countries where they took place.
151. 9:46But we can use a carbon footprint approach and allocate emissions
152. 9:50according to the country where the product is consumed.
153. 9:54If we take into account the net effect of trade,
154. 9:57we get this:
155. 9:58Some regions of the world reduce their emissions,
156. 10:01notably East Asia, to increase those of others,
157. 10:05notably developed countries.
158. 10:13Footprint or territorial approach,
159. 10:16taking into account only fossil CO2 or all greenhouse gases,
160. 10:21emissions per capita or per country, recent emissions
161. 10:26or cumulative past emissions.
162. 10:28The distribution and therefore our perception
163. 10:32of responsibilities change according to what we choose to look at.
164. 10:36This does not simplify international negotiations on the subject.
165. 10:41Now, let's leave the approach by groups of countries and look
166. 10:44at the human activities that emit these greenhouse gases.
167. 10:50When we look at the direct emissions of greenhouse gases by economic sector,
168. 10:54we note the important share of heat and electricity production.
169. 10:58Globally, electricity is still largely produced
170. 11:01with fossil resources, especially coal.
171. 11:04But we can attribute the emissions of heat and electricity production
172. 11:07to the sectors that consume them.
173. 11:11If we do this, we can see that at the global level,
174. 11:14industry, with 34% of direct and indirect emissions,
175. 11:18is the first sector to emit greenhouse gases.
176. 11:22If we look at these emissions in detail, we see that 8% of global emissions come
177. 11:27from the extraction and refining of metals.
178. 11:31After industry, we have buildings with 17%
179. 11:34of global emissions, including 11% for residential,
180. 11:40followed by transport with 15% of emissions, including 10% for road transport.
181. 11:51This is where we are today.
182. 11:54The emissions we are talking about here have not stopped increasing
183. 11:58over the last decades.
184. 11:59We must act quickly and in a sustained manner
185. 12:01in the coming decades if we want to limit warming to less than 2°C,
186. 12:05or even less than 1.5°C.
187. 12:08For that, the last part of the 6th IPCC report
188. 12:11identifies many actionable levers in the different sectors we mentioned.
189. 12:16For example, the possibility of having
190. 12:18more efficient equipment and buildings, among other things via the renovation
191. 12:22of buildings already built.
192. 12:24Gains can also come from behavioral changes, such as reducing meat consumption
193. 12:29in countries where it is high, or reducing car use in developed countries.
194. 12:35Significant reductions can be achieved through the deployment of technologies,
195. 12:38including low-carbon electricity generation:
196. 12:41wind, photovoltaic, hydro,
197. 12:45geothermal and nuclear.
198. 12:48Especially since low-carbon electricity opens the possibility of emission reductions
199. 12:54by electrifying transportation and heat production.
200. 12:57The most relevant levers vary from country to country
201. 12:59and depend on political choices.
202. 13:02It is hard to give a quick and global vision,
203. 13:05but we already have in our hands solutions that allow us to substantially reduce our
204. 13:10CO2 emissions over the next decades.
205. 13:14The question is whether we will be able to mobilize them fast
206. 13:16enough at the global level.
207. 13:23Well, I hope you've enjoyed this video
208. 13:26and now know a little more about global greenhouse gas emissions.
209. 13:30For those who would have liked a video on France, don't worry,
210. 13:33we are working on it.
211. 13:34And you will see that the sectoral distribution
212. 13:37of emissions is different from the one I have shown here at the global level.
213. 13:41I don't know if it's useful to remind you, but this is a vast and complex subject
214. 13:46and such a short format only touches it.
215. 13:48In addition to the sources, I'll leave you some links in the description
216. 13:52for those who want to go further.
217. 13:53This was Rodolphe Meyer for Le Monde. See you soon on the Net.