Prior to 1979, there were no formal announcements of business cycle turning points.
The NBER does not define a recession in terms of two consecutive quarters of decline in real GDP. Rather, a recession is a significant decline in economic activity spread across the economy, lasting more than a few months, normally visible in real GDP, real income, employment, industrial production, and wholesale-retail sales. For more information, see the latest announcement from the NBER's Business Cycle Dating Committee, dated 9/20/10.
The researchers involved — affiliated with the Marine Biological Laboratory at Woods Hole, Mass., the University of New Hampshire, the University of Massachusetts at Amherst and New Hampshire-based Research Designs — have continually measured the difference in carbon dioxide emissions emanating from the different plots. The hypothesis is that warmer temperatures would lead microorganisms in the soil to become more active in breaking down plant matter and other materials. These microbes would then release more soil carbon into the atmosphere in the form of carbon dioxide gas, in a process known as respiration.