I'm stumped on this sentence.
一度環境中に増えた二酸化炭素などの長寿命な温室効果ガスは、能動的に固定しない限り、約100年間(5年–200年[9])にわたって地球全体の気候や海水に影響を及ぼし続けるため、今後20–30年以内の対策が温暖化による悪影響の大小を大きく左右することになる[10]
My best attempt at this so far is. (If anyone could improve on this, it would be a big help.)
Greenhouse gasses like carbon dioxide with a long lifetime in the atmosphere, once released, will continue to have an effect on the climate and sea level over approximately 100 years until their emissions are limited. For this reason, the action taken on climate change in the next 20-30 years will have a big influence on the degree of their harmful consequences.
Edit:
I have updated the translation to accommodate the comments and answer below.
Greenhouse gasses like carbon dioxide with a long lifetime in the atmosphere, once released, will continue to have an effect on the climate and the oceans over an approximately 100 year period unless actively fixated. For this reason, the action taken on climate change in the next 20-30 years will have a big influence on the degree of such harmful consequences.
Edit 2:
Sorry; this is a reading comprehension question, not a translation question. I wasn't looking for the right translation or for proofreading. 能動的に固定しない限りwas the main barrier to my understanding, since it involved very technical Japanese and my dictionary wasn't very helpful.
However, my question was answered.