This is Scientific American 60-Second Earth. I'm David Biello. Your minute begins now.
Atmospheric carbon dioxide levels have now touched 400 parts per million and keep rising.
So who's responsible?
Scientists peg the start of this seemingly inexorable rise to about 1750, when people started burning coal to run steam engines.
But the CO2 increase also stems from activities like clearing forestlands for farming.
Now a new analysis assigns national blame for CO2 pollution and its ensuing global warming.
The seven biggest contributors both historically and today are, in alphabetical order: Brazil, China, Germany, India, Russia, the United Kingdom and the United States.
The report is in the journal Environmental Research Letters.
The undisputed champion of greenhouse gas pollution is no surprise: the U.S.
Our emissions to date mean we're responsible for 0.15 degree Celsius of the 0.8 degree Celsius rise in global average temperatures: 19 percent of the total.
That's more than twice as much as the next highest country, China.
The worst polluting country per person? The tiny U.K.
Unfortunately, China looks set to pass the U.S., unless their reliance on coal changes in short order.
As for us, after several years of our greenhouse gas pollution falling, CO2 emissions rose again in 2013.
Here's one area in which the U.S.shouldn't want to lead.
Your minute is up, for Scientific American 60-Second Earth. I'm David Biello.