The largest gap between any of the datasets in any year was 0.38ºF (0.21ºC), and the smallest gap was 0ºF/C: * To reconstruct global average temperatures in the era before instrumental measurements were made on a global scale, scientists use proxies that respond to changes in climate, such as the widths of tree rings and certain elements of the geological record, to estimate temperature variations in the past.  * The Intergovernmental Panel on Climate Change (IPCC) is a scientific body established in 1988 by the United Nations and World Meteorological Organization.It is the “leading international body for the assessment of climate change,” * The first IPCC report (1990) contains the following graph of average global temperature changes over the past 1,000 years based upon proxies.So it is important to recognize that natural variations of climate are appreciable and will modulate any future changes induced by man.* The second IPCC report (1995) states that “data prior to 1400 are too sparse to allow the reliable estimation of global mean temperature” and shows a graph of proxy-derived temperatures for Earth’s Northern Hemisphere from 1400 onward with different details but a similar overall trend to the first report. * The third IPCC report (2001) states that the latest proxy studies indicate “the conventional terms of ‘Little Ice Age’ and ‘Medieval Warm Period’ appear to have limited utility in describing …A caveat of this finding is that the feedback process operates “on a time scale of weeks,” and “it is not obvious whether similar behavior would occur on the longer time scales associated with global warming.”  * Other feedbacks that may have “a substantial impact on the magnitude, the pattern, or the timing of climate warming” include snow coverage, temperature gradients in Earth’s atmosphere, aerosols, trace gases, soil moisture changes, and ocean processes. * Per a 2003 report by the United Nations Food and Agriculture Organization, between the mid-1970s and late 1990s, apparent food consumption per person increased by 15% worldwide, 25% in developing countries, and more than 36% in China.Over this same period, world population increased by 45%, atmospheric CO2 increased by 10%, and the average global surface temperature (as calculated by NASA) increased by 0.9ºF (0.5ºC). found that a principal measure of worldwide vegetation productivity increased by 6.2% between 19.
The thesaurus of synonyms and related words is fully integrated into the dictionary.It shows a “Medieval warm period” that was warmer than the present era and a “Little Ice Age” that was cooler.The report states that: some of the global warming since 1850 could be a recovery from the Little Ice Age rather than a direct result of human activities.90% of the time, speakers of English use just 7,500 words in speech and writing.These words appear in red, and are graded with stars.