The Earthʹs past climate–including temperature and elements in the atmosphere–has recently been studied by analyzing ice samples from Greenland and Antarctica.

The air bubbles in the ice have shown that, over the past 160,000 years, there has been a close correlation between temperature changes and level of natural greenhouse gases carbon dioxide and methane. One recent analysis from Greenland showed that at the end of the last glacial period (when the great ice sheets began to retreat to their present position), temperatures in southern Greenland rose from 5 to 7 degrees in about 100 years.

Air bubbles are not the only method of determining characteristics of the Earthʹs ancient climate history. Analysis of dust layers from ancient volcanic activity is another such method; as is the study of ice cores, which interpret past solar activity that may have affected our climate.

Although the development of new infrastructure is usually determined by governmental planning, sometimes this development can be planned more flexibly and realistically by private investors who anticipate profit from the collection of user fees.

Such profits can contribute to the financing of more infrastructure if demand proves great enough, whereas the reluctance of developers to invest in such projects can signal that additional infrastructure is not needed. During the economic boom of the 1980’s, for example, the state of Virginia authorized private developers to build a $300 million toll road. These developers obtained the needed right-of-way from property owners, but by 1993 they still had not raised the necessary financing. The unwillingness of investors to finance this project does not negate the viability of privately financed roads; rather, it illustrates a virtue of private financing. If a road appears unlikely to attract enough future traffic to pay for the road, then it should not be built.