Have humans already changed the climate of earth?  As Cliff Mass of the University of Washington describes in his blog this week, “The answer is emphatically yes.”  But the changes are due to much more than just the addition of greenhouse gases like carbon dioxide into the atmosphere.  Our changes also have to do with irrigation, urbanization, travel, and other human activities.  You can read about all of these changes at https://cliffmass.blogspot.com/2015/04/human-alteration-of-climate-what-media.html.

Here in the Southeast, we attribute the “warming hole” or absence of long-term warming seen in other parts of the country at least in part to human land use changes over time.  A hundred years ago, there was a lot more bare soil in agricultural fields from cotton and other crops.  Now Georgia is over 70 percent forested as the boll weevil and increased agriculture in California moved a lot of the production westward.  Forests are cooler and moister than bare ground, which may have contributed to the long-term trends.  What will happen if California is no longer able to maintain its production due to water issues?  Will production move back east or will it move out of the country?  That is a topic of major interest for the future.

Contrails.  Source: Lamiot, Commons Wikimedia.
Contrails. Source: Lamiot, Commons Wikimedia.