The twentieth century is not the least bit climatically unusual. In more than three decades of attentive research Lamb's optimism ha s blossomed into facts about the last 1,000 years' climate change. With better tools and techniques, researchers have gathered comprehensive information about past climate change from proxies such as tree rings, pollen, coral, glaciers, boreholes, and sea sediments sampled worldwide.
Examples are geographically widespread and numerous.
In central Argentina during the LO, glaciers retreated and the plains regions turned warm and humid. During the LIA, glaciers advanced and the plains became cooler and semi-arid. That same region felt the chill of the LIA between 1550 and 1750 A.D., and that period was the coldest of the last 2000 years, according to oxygen isotope measurements in peat cellulose. The temperature in the interior of South Africa was higher by 3C during the LO and lower by 1C during the LIA compared with today, based on measurements of carbon and oxygen isotopes in stalagmites. The surface temperature of the Sargasso Sea in the North Atlantic exhibited a 1C rise 1,000 years ago and 1C decrease about 400 years ago, as shown by the level of the oxygen isotope in seafloor sediments.