When will production of oil and coal peak? After the peak, production will decline because supplies are being depleted and no new sources are to be found. Peak oil is the point in time when the maximum rate of global petroleum extraction is reached, after which the rate of production enters terminal decline. Optimistic estimations of peak production forecast the global decline will begin by 2020 or later, and assume major investments in alternatives will occur before a crisis, without requiring major changes in the lifestyle of heavily oil-consuming nations. These models show the price of oil at first escalating and then retreating as other types of fuel and energy sources are used. Pessimistic predictions of future oil production operate on the thesis that either the peak has already occurred, that oil production is on the cusp of the peak, or that it will occur shortly. The most recent edition of the respected science journal Nature contemplates the end of cheap coal with an analysis of the decline of global coal supplies by Post Carbon Institute Fellows David Fridley and Richard Heinberg. The estimates for global peak coal production vary wildly. Many coal associations suggest the peak could occur in 200 years or more, while scholarly estimates predict the peak to occur as early as 2010. Research in 2009 by the University of Newcastle in Australia concluded that global coal production could peak sometime between 2010 and 2048.