有事情可以做,但是他们会非常明显。1。一串成千上万的地球上有史以来最大的火山喷发发生。火山可以简单匹配人类输出,但是火山爆发几分钟或几小时。你需要相当于圣海伦火山喷发持续了70年。2。如果这个星球上每一个森林燃烧的。我相信人类会注意到这样一个风暴,和我,甚至不确定如果这就足够了。3所示。光合藻类的缓慢灭绝。 without the bulk of photosynthesis to convert co2 into oxygen it could build up. Of course we monitor this so it would not go unnoticed. More importantly oxygen levels would also drop dramatically which it hasn't. [https://scied.ucar.edu/imagecontent/carbon-cycle-diagram-ipcc][1] 4. The ignition and continuous burning of millions of miles of exposed coal beds. You would need to burn approximately ~3 teratons of coal. coal beds can be ignited by natural causes but we would notice a coal fire larger than a continent. 5. A drop in sea level by hundreds of feet would do it. large sea level drop cause outgassing of methane and co2, from wetlands and sea muds. but again New York would notice it if long island stopped being an island. Some of these have actually happen in earth's geologic history just none recently, and not as consistently as we have managed (at least not since life evolved). Really scientists have spent a lot of time and money looking for other causes, and no one has found any. Scientists concluded it was human activity by eliminating every other conceivable cause. [1]: https://scied.ucar.edu/imagecontent/carbon-cycle-diagram-ipcc