Question: From what you now know about global climate change, which of the following statements are true? Check all that apply. Based on the preceding graph, an atmospheric CO2 concentration of 396 ppm has been observed in the past 420,000 years. Increased cloud cover can potentially raise global temperatures by trapping more heat within the lower atmosphere. Oceans help absorb increasing amounts of CO2 from the atmosphere, but are in turn becoming more acidic.