used to infer historical temperatures, but generally in a more qualitative manner than natural proxies. Recent evidence suggests that a sudden and short-lived climatic shift between 2200 and 2100 BCE occurred in the region between Tibet and Iceland, with some evidence suggesting a global change. The result was a cooling and reduction in precipitation. This is believed to be a primary cause of the collapse of the Old Kingdom of Egypt. Satellite and balloon (1950s-present) Weather balloon radiosonde measurements of atmospheric temperature at various altitudes begin to show an approximation of global coverage in the 1950s. Since December 1978, microwave sounding units on satellites have produced data which can be used to infer temperatures in the troposphere. Several groups have analyzed the satellite data to calculate temperature trends in the troposphere. Both the University of Alabama in Huntsville (UAH) and the private, NASA funded, corporation Remote Sensing Systems (RSS) find an upward trend. For the lower troposphere, UAH found a global average trend between 1978 and 2019 of 0.130 degrees Celsius per decade. RSS found a trend of 0.148 degrees Celsius per decade, to January 2011. In 2004 scientists found trends of +0.19 degrees Celsius per decade when applied to the RSS dataset. Others found 0.20 degrees Celsius per decade up between 1978 and 2005, since which the dataset has not been updated. Thermometers (1850-present) See also Climate variability and change Global warming (causing recent climate change) CLIWOC (climatological database for the world's oceans) Dendroclimatology References External links Hadley Centre: Global temperature data NASA's Goddard Institute for Space Studies (GISS) — Global Temperature Trends. Surface Temperature Reconstructions for the last 2,000 Years Temperature History of climate variability and change Climate and weather statistics