Global Science Report is a weekly feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”
Many eyes will be on President Obama’s State of the Union address tonight watching to see how he follows his inauguration promise to “respond to the threat of climate change.” Rumors are flying that he will use his executive power to bypass Congress and further EPA efforts to regulate greenhouse gas emissions. But his best response would be to get the federal government out of the energy market and allow it to flourish as it may. The inconvenient truth is that the U.S. influence on global climate is rapidly diminishing as greenhouse gas emissions from the rest of the world rapidly expand. As a consequence, whether or not the United States reduces its emissions at all is immaterial to the path of future climate change and its impacts.
Several reports last week have shown that carbon dioxide emissions from the United States declined in 2012 and now stand at a level on par with what they were back in 1994. U.S. carbon dioxide emissions have dropped about 13 percent from their high in 2007.
All the while, global carbon dioxide emissions have been on the rise—primarily fueled by rapid emissions growth in developing countries, namely China (which is responsible for about two-thirds of the global increase during the past decade).
Since carbon dioxide is well-mixed in the atmosphere, who actually emits it is of little consequence when it comes to its potential to lead to global warming. This means that the global percentage of a country’s annual carbon dioxide emissions is equivalent to its annual percentage contribution to the increased warming pressure (we use the term “warming pressure” to indicate that things other than the atmospheric concentration of greenhouse gases also act to influence that global average temperature from one year to the next). Since total global carbon dioxide emissions are quickly distancing themselves from U.S. emissions, as time passes, the relative influence of U.S. emissions on the future state of the global climate is rapidly declining.