Scientists at the Harvard-Smithsonian Center for Astrophysics took a look at how weather has changed in the past 1,000 years. They looked at studies of changes in glaciers, corals, stalagmites, and fossils. They checked investigations of cores drilled out of ice caps and sediments lying on the bottom of lakes, rivers, and seas. They examined research on pollen, tree rings, tree lines, and junk left over from old cultures and colonies. Their conclusion: We are not living either in the warmest years of the past millennium nor in a time with the most extreme weather. This review of changes in nature and culture during the past 1,000 years was published in the April 11, 2003 issue of the Journal of Energy and Environment. It puts subjective observations of climate change on a much firmer objective foundation. For example, tree-ring data show that temperatures were warmer than now in many far northern regions from 950 to 1100 A.D. From 800 to 1300 A.D., the Medieval Warm Period, many parts of the world were warmer than they have been in recent decades. But temperatures now (including last winter) are generally much milder than they were from 1300 to 1900, the Little Ice Age.