二氧化碳(CO2)。二氧化碳是大气中微小但非常重要的组成部分，通过呼吸和火山爆发等自然过程以及森林砍伐、土地利用变化和燃烧化石燃料等人类活动释放。自工业革命开始以来，人类已使大气中CO2浓度增加了三分之一。这是最重要的长寿的“逼格”;气候变化。< / p >
An article by NC State University says that a healthy tree can store 13 pounds of carbon per year. As I understand it, carbon dioxide is processed by the tree: the carbon is stored, and the oxygen released.
Given that, how many trees would I need to plant to solve the global climate change crisis? Should I optimize for a specific type of tree, or would pine work as well as oak or black walnut?
There is also the problem that forested land is likely to have a lower albedo than the land surface that it covers, and hence the planet will reflect less sunlight back into space which would lead to some extra warming, so we would also need to compensate for that somehow. Apparently about 26% of Earth's land is already covered with forests. I rather doubt over half of the uncovered land surface is suitable for new forests, the continents have large bands either side of the equator that are generally too arid, and the regions close to the poles are too cold.
In short, it isn't going to work, even with the most generous assumptions about forest CO2 exchanges (unless of course I have made an arithmetic error, which is definitely a possibility).
首先，你需要把它看作一个森林。在森林中，除了获胜的树外，也有在进化游戏中失败的树。< / p >
Second, you need to look where (in terms of climate) your forest is, and what's its soil. This defines the tree type.
Third, you need to cut your forest on time to optimize it' growth rate. 26 years is optimum, so roughly 4 times a century.
This way you can reach growth rates like 4.8 tn/ha/year in Finland or
5.16 tons/acre/year in the USA. I am not sure about the unit used in this source, but if their ton is 907 kg and an acre is 4046.85 m$^2$, this results in 11.56 tn/ha/year.
If the used carbon amount is $9.2 \times 10^9$ tons, and half of wood weight is carbon then you need $1.6 \times 10^9$ ha or 16 000 000 km$^2$ of forest.
There is 39 500 000 km$^2$ of forest in the world. If 40% of it is used optimally, it would be enough at present rates. The CO$_2$ concentration is not a problem; human population growth is.
In essence, new calculations show that NCS (natural climate solutions: a combination of land management, forestation, etc):
...can provide over one-third of the cost-effective climate mitigation needed between now and 2030 to stabilize warming to below 2 °C.
Source: Griscom et al (2017), Natural climate solutions, PNAS, https://doi.org/10.1073/pnas.1710465114
However!
Turns out that trees, other than sequestering carbon, also emit volatile organic compounds (VOC) that act as greenhouse gases. Therefore, the answer isn't as simple as planting trees.
Quoting some recent articles on the subject:
Many scientists applaud the push for expanding forests, but some urge caution. They argue that forests have many more-complex and uncertain climate impacts than policymakers, environmentalists and even some scientists acknowledge. Although trees cool the globe by taking up carbon through photosynthesis, they also emit a complex potpourri of chemicals, some of which warm the planet. The dark leaves of trees can also raise temperatures by absorbing sunlight. Several analyses in the past few years suggest that these warming effects from forests could partially or fully offset their cooling ability.
Source: Gabriel Popkin (2019), How much can forests fight climate change?, Nature, http://doi.org/10.1038/d41586-019-00122-z
and
That doesn’t mean that all forests cool the planet, however. Researchers have known for decades that tree leaves absorb more sunlight than do other types of land cover, such as fields or bare ground. Forests can reduce Earth’s surface albedo, meaning that the planet reflects less incoming sunlight back into space, leading to warming. This effect is especially pronounced at higher latitudes and in mountainous or dry regions, where slower-growing coniferous trees with dark leaves cover light-coloured ground or snow that would otherwise reflect sunlight. Most scientists agree, however, that tropical forests are clear climate coolers: trees there grow relatively fast and transpire massive amounts of water that forms clouds, two effects that help to cool the climate.
Source: Gabriel Popkin (2019)
and
Atmospheric chemist Nadine Unger, then at Yale University in New Haven, Connecticut, conducted one of the first global studies examining one part of this exchange: the influence of volatile organic compounds, or VOCs, emitted by trees. These include isoprene, a small hydrocarbon that can warm the globe in several ways. It can react with nitrogen oxides in the air to form ozone — a potent climate-warming gas when it resides in the lower atmosphere. Isoprene can also lengthen the lifetime of atmospheric methane — another greenhouse gas. Yet isoprene can have a cooling influence, too, by helping to produce aerosol particles that block incoming sunlight.
Source: Gabriel Popkin (2019)
and
Plants take up carbon dioxide and release volatile organic compounds (VOCs), in a similar way to how other organisms breathe in oxygen and exhale CO2. These VOCs are oxidized in the atmosphere and then contribute substantially to the burden of tiny particles suspended in the air, which are known as aerosols. Aerosols produced from VOCs are known as secondary organic aerosols (SOAs), and affect both air quality and Earth’s climate. The total rate of SOA production was thought to be the sum of the individual rates associated with the oxidation of each VOC. But writing in Nature, McFiggans et al.1 show that a more accurate description is needed to improve the representation of SOAs in computational models of air quality and climate.
Fangqun Yu (2019), Atmospheric reaction networks affecting climate are more complex than was thought, Nature, https://doi.org/10.1038/d41586-019-00263-1
Sources of the articles:
无，热带幼树除外。总的来说，树木是碳中性的。木材/生物质必须通过地质隔离来长期储存碳。这需要一棵