The Earth's heat balance is such that without the atmosphere, the average temperature on our planet would be -18 °C. But now the average annual temperature is 15 °C. The difference of 33 degrees is considered a greenhouse effect. It is interesting that in the ice age, the average temperature was only 4 degrees lower: we can imagine that the Earth would be at -18 ° C - a ball of ice, not suitable for life.
Short-wave radiation comes from the Sun, and our atmosphere lets it through completely. Only the harsh ultraviolet rays are trapped by oxygen. When the Earth heats up, it emits long-wave radiation, and our atmosphere is no longer transparent to this type of radiation. Longwave radiation is trapped by some gases: about 31 degrees of the 33-degree difference in the greenhouse effect is due to water vapor. Human activity enhances the greenhouse effect by emitting CO2 - relevant measurements of CO2 levels, which have been made since 1959, show a steady increase in this parameter.
Since the beginning of the century, the average temperature on Earth has increased by 0.75 degrees. This does not seem like much, but we should not forget that a difference of only 4 degrees led to the Ice Ages. That is why international agreements set a limit on temperature growth: 2 degrees is the limit we must not cross. In order to achieve this, we have to cut CO2 emissions by 70%. That is impossible because you would have to stop the world's energy industry and therefore the economy. This is why many people believe that the only way is to find technological ways to reduce not emissions, but the CO2 content in the atmosphere.
Different projects are being developed for this purpose.
Some of them suggest pumping CO2 out of the atmosphere and burying it in waste mines. The second way is to plant fast-growing trees that will absorb CO2. However, the trees themselves would then also have to be buried. The third way is to reduce the influx of sunlight. To do this, it is necessary to fly into the stratosphere at a height of 10-15 thousand meters and spray some particles. When a large volcano erupts, the ash particles cool the Earth for another three years after the eruption. By analogy, it is usually proposed to use small silver particles, which will also actively reflect the sun's rays. Of course, this method is not the most convenient. First, you would have to spray silver continuously over the entire planet. Secondly, if the spraying ends, there will be a very sharp temperature increase. So right now, the climate situation is almost stalemated. There is no real way to combat atmospheric CO2.
We just wait and watch the temperature rise.
Climate change is a gradual process, and our adaptation to these changes is relatively rapid. Mankind has already experienced similar warming and cooling eras, and there is no reason to panic. Warming of more than 2 degrees already took place in the Northern Hemisphere between 1000 and 1300. It was then that Greenland was discovered and populated, which is why it received such a strange name by today's standards. Around the same time, vineyards were growing in England and wine was being made there - hard to imagine now. And then the warm era was replaced by the Little Ice Age, which lasted until the middle of the nineteenth century. It was so cold that the Thames River froze regularly.
The climate is constantly changing. It gets warmer and colder on Earth because atmospheric circulation fluctuates. The ratio of air mass coming from the ocean or forming on continental land can vary. Since the 1970s, warming has been exacerbated by anthropogenic accumulation of CO2 in the atmosphere, but the next ice age will definitely happen, albeit in 10,000 years.
The Intergovernmental Panel on Climate Change has been in existence since 1988. Every two or three years it publishes reports summarizing all climate research. Now many climate models have been created to increase the average annual temperature. In 2015, the Paris Agreement was adopted, under which each country made commitments to reduce CO2 emissions. It was under this agreement that the temperature increase threshold was announced. For island nations, a warming of even 2 degrees is already too dangerous. If the ocean starts to rise, the islands will experience salinization of groundwater and the main sources of fresh water. That is why they were in favor of lowering the official permissible threshold to 1.5 degrees, but for the rest of the countries it is too hard a limit, which is practically unattainable.
The greatest climate risk occurs in countries with small territories. Their entire economy is adapted to one climate, and in case of major climate changes there is no room for maneuver, no space to relocate, for example, agriculture. If the water level rises in the Netherlands, they will have to build more dams. If desertification starts in Africa, it will be impossible to influence it, and there will be waves of migration.
It is important to realize that there is no real way to fight climate change yet. Despite the agreements, the Paris commitments will lead to a warming of the planet by more than 3.5 degrees, because no country wants to limit itself economically. But there is hope that mankind will adapt to the situation quickly enough. There is enormous scientific potential in the world, and the same biotechnology can fundamentally change agriculture. We have time, and we can remain optimistic about the problem of climate change.