Atmospheric carbon dioxide reaches 400 parts per million concentration milestone
Text-Dependent Questions
1.
2.
3.
4.
5.
6.
Why are atmospheric CO2 levels of 400 ppm a significant milestone?
How do we determine atmospheric CO2 levels?
Is there a historical precedent for the levels of atmospheric CO2 that are present today?
How do past periods with high atmospheric CO2 levels compare to conditions today?
Why are high levels of atmospheric CO2 a concern?
What can humans do to slow this trend?
Article link:
http://www.washingtonpost.com/blogs/capital-weather-gang/wp/2013/05/10/atmosphericcarbon-dioxide-concentration-400-parts-per-million/