New paleoclimatic evidence of an extraordinary rise in temperature in the Northern Hemisphere in the last 3–4 decades

Abstract

ABSTRACT Prognosis of temperature changes in the Northern Hemisphere for the period 1980–2020 was made using seven temperature paleoreconstructions covering the last 1–2 millennia and ending 1979–2016. Forecasts were made using the analogue nonlinear prediction method. A part of paleodata before 1800 (prior to the beginning of anthropogenic impact) was used as an information bank. In all seven cases, the forecast gave either a decrease or a very slight increase in temperature during 1980–2020. Statistical experiments performed with using prediction errors based on a conservative estimation of reconstruction uncertainties showed that a temperature increase of 0.25°C in the specified epoch is not excluded, but its probability is low (P < 0.20). This means that if the climate in the 20th - early 21st century was controlled by the same dynamic system as before 1800, the noticeable warming of the Northern Hemisphere in 1980–2020 should not be observed. Thus, it was shown that the data of modern paleoclimatology confirm that the climate of the Northern Hemisphere in the last 40–50 years was significantly influensed by an additional factor that did not act in the previous 1–2 millennia. It was also shown that if the actual uncertainties are significantly higher than the conservative estimates used, a warming of 0.5 degrees between 1980 and 2020 due to internal climate variability becomes possible.