二氧化碳水平指的是全球对流层中二氧化碳的浓度分布，一般以百万分之一为测量单位。
根据美国宇航局夏威夷莫纳罗亚天文台的读数，在2019年5月，人类历史上二氧化碳水平首次达到415 ppm。上一次地球的二氧化水平在这一浓度时，大约是300万年前，那时候海平面比现在高出了25米。
二氧化碳是一种重要的温室气体，通过人类活动，如焚烧森林、燃烧化石燃料以及其他自然因素，如呼吸和火山爆发等形式释放出来。
地球的温度上升已经不能用自然因素来解释了。人类活动向大气中排放的二氧化碳达到前所未有的水平，地球气候将发生剧烈变化，导致海平面上升、洪水泛滥、风暴和干旱等，这些气候问题正日益严重地威胁人类的生存。
Carbon dioxide level measures global distribution and variation of the concentration of mid-tropospheric carbon dioxide in parts per million (ppm).
According to the readings taken at NASA’s Mauna Loa Observatory in Hawaii, carbon dioxide level on earth have officially hit 415 ppm in May 2019. This is the first time in human history that carbon dioxide level has reached 415 ppm. At the previous time when earth’s carbon dioxide was at this level of concentration, the sea levels were 25 meters higher. That happened around 3 million years ago.
Carbon dioxide is an important heat-trapping (greenhouse) gas, which is released through human activities such as deforestation and burning fossil fuels, as well as natural processes such as respiration and volcanic eruptions.
Earth’s temperature rise could no longer be explained by natural factor. With the unprecedented amount of carbon dioxide released into the atmosphere due to human activities, earth climate will change drastically and cause sea level rises, flooding, severe storms and droughts among other problems, threatening human survival.
