The tundra is a biome on the Earth that covers approximately 20% of its land mass, and it is almost exclusively located in the Northern Hemisphere. It is an environment that helps in the regulation of the CO2 in the atmosphere, and it is one of the biggest natural CO2 sinks. The living organisms in the tundra, are using the CO2 for their needs, thus removing parts of it from the atmosphere, and when they die, because the tundra is cold, and the decomposition is very slow, most of the CO2 remains trapped, and doesn't go into the atmosphere.
Unfortunately, the global warming is slowly changing the tundra, and prolongs the summer periods, thus reducing the permafrost period of the year, so the decomposition of the living organisms is getting quicker, and also bigger percentage of the CO2 from them gets to the atmosphere.
3000 is the correct evelation. If you follow the line Z is one, you end up with 3000.
