The UN's IPCC and associated climate doomsday scientists attempted to convince policymakers and the public that extreme climate change was occurring in the modern world world and that it was "unprecedented" - the historical empirical evidence does not support that conclusion
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Read here. The UN's IPCC is not a climate science research agency. Instead, it is a bureaucratic political agency charged with "proving" human greenhouse gases (ie, CO2 emissions) are causing "unprecedented" global warming and climate change.
It conducts no original research, instead relying on cherry-picked peer reviewed studies and non-peer reviewed reports from green activist organizations. It prefers research studies that happen to also rely on cherry-picked data and/or flagrantly absurd statistical methodoloiges that produce the infamous hockey-stick presentation of past temperatures. The classic case of this IPCC-style of science, that's since been discredited, is this study and the most recent hockey-stick fiasco that had to be withdrawn is this one.
Because of the easy access to knowledge and information that the internet now provides, we can also discover the past and more current peer reviewed studies that the IPCC chose to avoid, ignore or dismissed because they did not support the political objective of proving the climate evils of CO2 greenhouse gases. One such report from the past that was ignored was conducted by Japanese researchers, which confirmed that modern climate change was not unusual but part of a natural pattern.
"In the early 1990s, Japanese scientists Kitagawa and Matsumoto extracted eleven tree ring cores from cedars on the...Japan island of Yakushima. The cores contained tree-rings going back some 2000 years. The researchers determined the carbon 13 isotope values and found the delta-13-C values fluctuated in a characteristic manner...The results showed that temperatures over the previous 2000 years in South Japan fluctuated over a range of 5°C...A clear millennium cycle is depicted. The cold period of the Migration Period, the Medieval Warm Period, the Little Ice Age and the Modern Warm Period are clearly recognisable. Moreover, this climate development is well documented in Japanese historical records...They carried out a detailed frequency analysis of their data and found characteristic cycles with periods in the range of several decades and centuries. Among others, they discovered a period of 187 years, which coincides with the known Suess/de Vries solar activity cycle. In a similar manner the 70 and 89-year Gleissberg-cycle was identified." [Hiroyuki Kitagawa and Eiji Matsumoto 1995: Geophysical Research Letters]