CLIMATE CHANGE: LONG-TERM TRENDS AND SHORT-TERMOSCILLATIONS

Identifying the Northern Hemisphere (NH) temperature reconstruction and instrumental data forthe past 1000 years shows that climate change in the last millennium includes long-term trends and variousoscillations. Two long-term trends and the quasi-70-year oscillation were detected in the global temperatureseries for the last 140 years and the NH millennium series. One important feature was emphasized thattemperature decreases slowly but it increases rapidly based on the analysis of different series. Benefits can beobtained of climate change from understanding various long-term trends and oscillations. Millennial temperatureproxies from the natural climate system and time series of nonlinear model system are used in understanding thenatural climate change and recognizing potential benefits by using the method of wavelet transform analysis. Theresults from numerical modeling show that major oscillations contained in numerical solutions on theinterdecadal timescale are consistent with that of natural proxies. It seems that these oscillations in the climatechange are not directly linked with the solar radiation as an external forcing. This investigation may concludethat the climate variability at the interdecadal timescale strongly depends on the internal nonlinear effects in the climate system.