We have another Twitter chat today on climate change: 2pm ET. Where:@EarthVitalSigns. Topics: greenhouse...

We have another Twitter chat today on climate change: 2pm ET. Where:@EarthVitalSigns. Topics: greenhouse gases & global warming. Ask questions: #askclimate. For more on our "Ask A Climate Scientist" campaign: http://youtu.be/49Lu1dTa0_k