During the week of May 13th, the CO2 level at the Mauna Loa Observatory in Hawaii topped 400 ppm repeatedly. Daily levels of CO2 can vary due to weather, and there are seasonal trends as well.
Free Entry to National Parks April 17-25, 2010
The National Park Service is waiving entrance fees, so visitors can enjoy all 392 national parks for free April 17-25.
Find a park near you at www.nps.gov
