In order to study the reason why global warming is happening. Why 142 billion tone CO₂ is remaining to give global warming. Why fish production of Japan decreased. I investigated CO₂ emission, NOx emission, grain production, fish production , CO₂ fix and CO₂ increase of many countries. About 380 billion tone CO₂ is fixed by CO₂ assimilation. 142 billion tone CO₂ is remaining to give global warming. Then I found that many developed countries are eliminating NOx. About half of produced NOx 7.2 billion tone is eliminated. Then CO₂ assimilation is retarded. CO₂ fix is retarded. And 142 billion tone CO₂ Is remaining to give global warming. Japan producing 12.5 billion tone CO₂ and 0.5 Billion tone NOx. Japan eliminating all of 0.5 billion tone NOx Then CO₂ assimilation is retarded. Plankton production is retarded.. Fish production of Japan decreased to 10 % since NOx elimination and NP elimination of wast water. Therefore Japan lost 0.12 billion tone fish production, 2.4 billion tone CO₂ fix by plankton CO₂ assimilation. If developed countries stop elimination of NOx and NP in waste water, then 142 billion tone CO₂ can be fixed. And CO₂ emission produced by elimination of NOx,NP is saved . By promotion of plankton CO₂ assimilation by increasing NP concentration at sea, fish production increase and global warming can be protected. Complete use of NOx and NP are essential for the increased production of food and protection of global warming.