Paleo Slide Set: Polar Ice Cores
Non-Sea Sulfate and Nitrate Concentrations since 1900

Records of recent human activities are also stored in the Greenland Ice Sheet. Research from 
the top layers of the ice sheet shows how concentrations of nitrates (NO3-) and non-sea salt sulfates 
have increased dramatically since 1900 A. D. Sulfates and nitrates are released when fossil fuels are 
burned. They react with water in the atmosphere to form sulfuric and nitric acids (H2SO4 and HNO3, respectively), 
two of the leading components of acid rain (rain is naturally mildly acidic; the term acid rain is used to refer 
to precipitation with acidity higher than that occurring naturally). It is one of the great ironies of contemporary 
climatology that the huge quantities of sulfates released into the air by fossil-fuel burning may be helping to 
counteract the so-called Greenhouse Effect, the warming of the atmosphere anticipated because of increased carbon 
dioxide concentrations emitted during the very same burning of fossil fuels. One of the driving forces behind 
paleoclimatic research is the desire to gain a greater understanding of the climate system in the hopes of 
anticipating and/or preventing the possible adverse effects human activities may have on the environment. 
If anything is to be learned from the GISP2 project, perhaps it is this: Earth's climate has been very unstable 
in the past, and our understanding of the climate system is currently not advanced enough to know what caused 
this instability. Is it possible that the activities of human beings could usher in yet another era of climatic 
instability?

Data from GISP2 and dozens of other ice cores from polar and alpine areas are important tools in the search for 
answers to these crucial questions. 

Photo Credits:
Graphic produced by Thomas Andrews using data from Mayewski et al. (1986 and 1990). 
NOAA Paleoclimatology Program