What are the implications of global climate change and what can we do about it? Looking at average temperatures during the past 150 years, the global average temperature of the earth began to rise between 1850 and 1910. From 1910 to 1940, the global average increased about .4 degrees. However, if you look at the recent climate record, there is a sense of an accelerated warming trend. Nine of the warmest years in the last 150 years were in the 1990's.

Yet, how do we know if the increase in temperature is really caused by humans, rather than by a natural phenomenon? For example, a thousand years ago, the earth experienced a relatively warm period called the Medieval Optimum. This warm period ended in 1200 or 1400, after which the earth plunged into what is known as the Little Ice Age. That ended at the beginning of the Industrial Revolution, its ending coincidentally coinciding with the increase of CO2. The earth is warmer today than at any time during the past 1,500 years, and perhaps longer. Yet, modeling the climate scientifically is a very complicated problem, and firm conclusions about the rate and scope of climate change are often illusory. At present, we do not know enough about our climate to be absolutely confident of the predictive abilities of our climate model.