Samma på svenska https://larsschnellsblogg.blogspot.com/2025/11/eus-vag-fordonsflotta-slapper-ut-ca-764.html
I posed the same two questions to two AIs.
1. What are the estimated annual CO₂ emissions from EU road traffic vehicles?
2. How many trees does this correspond to (with an assumed CO₂ sequestration of approximately 25 kg per tree per year, given after a certain size)?
ChatGPT (without subscription)
Answer 1)
Road traffic total (EU-27): ≈ 764 million tonnes of CO₂ equivalents per year (Includes passenger cars, light commercial vehicles, heavy-duty vehicles, and buses.)
Passenger cars (only): ≈ 450 million tonnes of CO₂ per year (Approx. 13% of total EU emissions.)
Answer 2) Calculation: Road traffic emissions: 764 million tonnes of CO₂/year A tree can sequester approximately 25 kg of CO₂/year = 0.025 tonnes of CO₂/year Number of trees required: 764,000,000 tonnes ÷ 0.025 tonnes per tree = 30,560,000,000 trees
≈ 30.6 billion trees Therefore, approximately thirty billion trees are needed to offset EU road traffic emissions on an annual basis, assuming each tree is mature and sequesters 25 kg of CO₂ per year.
Gemini (with subscription)
Answer 1) Greenhouse gas emissions from road transport in the EU’s 27 Member States amount to over 700 million tonnes of carbon dioxide equivalents (MtCO2e) per year. Here is a more detailed insight based on available data from EU sources (although exact figures vary slightly depending on the source and measurement year): Order of Magnitude: The transport sector (including road traffic, aviation, shipping, rail) accounts for a significant portion of total EU emissions. Road traffic is the largest source within the transport sector. Historical Data: Before the pandemic, road traffic emissions were at a level around 700–750 MtCO2e per year. During 2020 and 2021, emissions temporarily decreased due to the pandemic, but they have since tended to increase again. EU Goal: The EU aims to reduce transport emissions by 90 percent by 2050 compared to 1990 levels, as part of the European Green Deal. Road transport accounts for the majority of transport emissions in the EU, and they have proven difficult to reduce quickly.
Answer 2) That is an interesting comparison!
With the figure you provided, 25 kg of CO₂ sequestration per tree per year, we can do an estimation. (It is important to note that 25 kg CO₂/year is a common standard for an average, growing tree, but the exact amount varies greatly depending on tree species, age, size, and location.)
We previously used the estimate that EU road traffic emits over 700 million tonnes of carbon dioxide equivalents (MtCO2e) per year. Let us use 700 MtCO2e for the calculation.
Calculation
Convert tonnes to kg: 700 million tonnes = 700 × 10⁹ kg CO₂e
Divide the total emissions by the sequestration capacity per tree: Number of trees = Total emissions in kg / Sequestration per tree in kg Number of trees = 700,000,000,000 kg / 25 kg/tree Number of trees = 28,000,000,000 trees
Conclusion
To sequester the annual emissions of approximately 700 MtCO₂e from EU road traffic, it would theoretically require 28 billion trees that each sequester 25 kg of CO₂ per year.
This illustrates the immense scale of emissions from road traffic. By comparison, Sweden has an estimated total of 87 billion trees, but a large proportion of these trees have already reached their maximum growth and therefore no longer sequester carbon dioxide at this high rate.
The interesting thing here is that Sweden has 3 times as many trees as would need to be planted to offset the annual CO₂ emissions of the EU's 27 Member States. So the next question to the AI is: what area would this correspond to/cover in coastal/river-near areas in, for example, the Sahara, and how long would it take to produce these plants, which should be fast-growing species?
Chat GPT
Answer 3) Assumptions and starting points (clear and brief): Need: 30.56 billion trees (previous calculation). Sweden: 87 billion trees → one third ≈ 29 billion trees (close to the need). Planting density (common range for fast-growing plantations): 500 / 1,000 / 2,000 trees per hectare. Conversions: 1 ha = 0.01 km², 1 km² = 100 ha.
Area required for 30.56 billion trees (various densities) | Density | Area (ha) | Area (km²) | % of Sahara (~9,200,000 km²) | | :--- | :--- | :--- | :--- | | 500 trees/ha | 61,120,000 ha | 611,200 km² | ≈ 6.6 % of Sahara | | 1,000 trees/ha | 30,560,000 ha | 305,600 km² | ≈ 3.3 % of Sahara | | 2,000 trees/ha | 15,280,000 ha | 152,800 km² | ≈ 1.7 % of Sahara |
Time until trees provide intended sequestration (fast-growing species) — realistic range:
Production of seedlings in nursery: 0.5–2 years (depending on species and method).
Survival and establishment in the field (especially in dry areas): the first 1–3 years are critical; significant mortality without irrigation/measures.
Timeframe to significant carbon uptake ≈ 25 kg CO₂/tree/year: typically 5–15 years in favorable, irrigated, and nutrient-enhanced conditions; in marginal, semi-arid conditions, it may take 10–20+ years or never reach full effect without constant maintenance.
Summary (concrete): To plant ~30.6 billion trees in coastal/river-near parts of the Sahara, you need approximately 153–611 thousand km² depending on planting density (2,000–500 trees/ha). Producing the seedlings takes 0.5–2 years in the nursery; reaching full sequestration capacity (~25 kg/year/tree) takes approx. 5–15 years in good conditions (longer in arid conditions) and requires extensive irrigation and maintenance.
Gemini
Answer 3)
It is a thought-provoking idea to compare the necessary number of trees with Sweden's total forest stock, and then to place them in a challenging area like the Sahara. Let us divide the answer into three parts:
Calculation of the area required.
Estimate of the time required to grow the seedlings.
Climatic and logistical challenges (especially in the Sahara).
🌳 1. Calculation of the area required You stated that approximately 28 billion trees would be needed. We use a moderately conservative assumption for effective afforestation: Assumption: We plant 1,500 trees per hectare.
Calculation Total area (hectares) = Number of trees / Trees per hectare Total area (hectares) = 28,000,000,000 / 1,500 trees/ha ≈ 18,666,667 hectares
Comparison in square kilometers 18,666,667 hectares × 0.01 km²/hectare = 186,667 km²
Answer on area: The 28 billion trees would cover an area of approximately 187,000 square kilometers (187,000 km²). This corresponds to approximately 42% of Sweden's total land area. It is roughly the size of the country Syria or the state Florida (USA).
🌱 2. Time required to grow the seedlings If one were to build a production chain that could deliver 1 billion seedlings per year (which is itself an enormous goal), it would take 28 years to produce the total number of seedlings.
🌊 3. Challenges in coastal/river-near areas in the Sahara Placing the forest in the Sahara creates enormous challenges that are not just about the tree's CO₂ sequestration, but about its survival: Water (The critical problem): Access to sufficient freshwater to establish and maintain 187,000 km² of forest in an arid climate is extremely demanding. Solution: Massive desalination projects or large-scale irrigation from underground sources/rivers would be necessary. Soil: Sandy desert soil often lacks the nutrients and water retention capacity required to rapidly establish a large forest. Solution: Significant soil improvement would be necessary.
The challenges are water, soil improvement until foliage, soil biotope, etc., take over, and the number of plants needed. The solutions are solar-powered desalination plants and the millions of people in nearby areas who could get jobs, partly with planting machines, desalination equipment, and growing seedlings. I believe that with an offensive approach against drought and all the problems this solves around the world, it will not take 28 years, and if so, we should start immediately. One can also take national responsibility – so that everyone understands that one does not shut down nuclear reactors when the electricity is needed for electric vehicles – but instead co-plans the purchase of equipment.
If it gets very hot and all the glaciers melt away during that time – with major disruptions, including to the Gulf Stream – then one must simply simulate a large volcanic eruption with harmless aerosols that reduce the shortwave radiation from the sun.
I started writing letters to the editor about desert plantings over 20 years ago to counteract wars over scraps, deadly pension systems, and if one had started then, one would have been forced to protect deserts from tree plantings if several countries understood that drought on a water planet will be difficult to explain to some UFO crew that lands.
I know there are other problems like salt intrusion, albedo values, etcetera, but solve them as they arise and start planting now. As mentioned, there are emergency solutions like simulated cooling volcanic eruptions = Stratospheric Aerosol Injection (SAI).
| Layer (Sphere) | Approximate Height | Temperature Trend | Key Features |
| 1. Troposphere | 0 to approx 8-15 km | Decreases with height. | Contains almost all water and is where all weather occurs. It is turbulent and has vertical air movement. |
| 2. Stratosphere | approx 15 km to approx 50 km | Increases with height. | Contains the ozone layer, which absorbs UV radiation and causes the temperature increase. Airflow is stable; the location for SAI (geoengineering). |
| 3. Mesosphere | approx 50 km to approx 85 km | Decreases with height. | The coldest layer in the atmosphere (temperature can drop to -90 °C). Where most meteors burn up. |
| 4. Thermosphere | approx 85 km to approx 600 km | Increases sharply with height. | Air molecules are extremely few, but they are highly energetic (hot). This is where the aurora (Aurora Borealis/Australis) occurs. The International Space Station (ISS) orbits in this layer. |
| 5. Exosphere | approx 600 km and up | Variable. | The outermost boundary of the atmosphere, where molecules can escape into space. The thin atmosphere gradually transitions into space. |
The Great Green Wall (Stora Gröna Muren)
How long has it been going on?
Launch: The initiative was officially launched by the African Union (AU) in 2007.
History: The idea of planting a line of trees to stop the desert has, however, existed for several decades.
Development: Over the years, the project has evolved from being a simple "wall" of trees to becoming a broader, integrated development program focusing on sustainable land management, water harvesting, and the creation of green, productive landscapes.
| Goal by 2030 | Results Achieved (Approximate, at latest measurements) |
| Restored land area: 100 million hectares | Over 25 million hectares (some sources mention up to 60 million hectares restored land depending on definition). |
| Trees planted: No official total goal for the number of trees, but the ambition is gigantic. | 26.4 million trees (specific projects contribute many more). Individual partner organizations have planted tens of millions of trees. |
| Carbon sequestration: 250 million tonnes | Ongoing process. |
| Create green jobs: 10 million jobs | Over 20,000 jobs created, with an ambition to scale up enormously. |
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